TY  - JOUR
AU  - Gnjatović, Nebojša
AU  - Bošnjak, Srđan
AU  - Stefanović, Aleksandar Z.
PY  - 2023
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/4903
AB  - Continuous earthmoving machines, such as bucket-wheel excavators (BWEs), are the largest mobile terrestrial machines exposed to the working loads of a periodic character. This paper aims to launch a new idea regarding the preservation of the load-carrying structures of these machines by the means of implementing a controllable frequency-controlled drive of the excavating device. Successful implementation of this idea requires a detailed analysis of the dynamic response of the load-carrying structure in order to determine the domains of frequency of revolutions of the bucket-wheel-drive electromotor (FREM) where the dynamic response of the structure is favorable. The main goal of the presented research was the development of a unique three-step method for the identification of the FREM ranges, where the vibroactivity of the load-carrying structure is within the allowed boundaries. A methodologically original study of the dynamic response was conducted on a unique dynamic model of the BWE slewing superstructure that allows for continuous variation of the FREM, i.e., of the frequency of excitation caused by the forces resisting the excavation. Validation of the spatial reduced dynamic model of the slewing superstructure and the corresponding mathematical model, as well as the overall approach to the determination of the dynamic response, were performed by the means of vibrodiagnostics under the real exploitation conditions. Application of the developed method has yielded: (1) the resonant-free FREM domains; (2) the FREM domains, where the structure is not exposed to the excessive dynamic impacts; and (3) the frequency ratio ranges defining the resonant areas. Additionally, the results of the research have pointed out that the resonant-free state represents a necessary but insufficient condition for the proper dynamic behavior of the BWE slewing superstructure.
PB  - MDPI (Basel, Switzerland)
T2  - Mathematics
T1  - Analysis of the Dynamic Response as a Basis for the Efficient Protection of Large Structure Health Using Controllable Frequency-Controlled Drives
IS  - 1
SP  - 154
VL  - 11
DO  - doi.org/10.3390/math11010154
ER  - 

@article{
author = "Gnjatović, Nebojša and Bošnjak, Srđan and Stefanović, Aleksandar Z.",
year = "2023",
abstract = "Continuous earthmoving machines, such as bucket-wheel excavators (BWEs), are the largest mobile terrestrial machines exposed to the working loads of a periodic character. This paper aims to launch a new idea regarding the preservation of the load-carrying structures of these machines by the means of implementing a controllable frequency-controlled drive of the excavating device. Successful implementation of this idea requires a detailed analysis of the dynamic response of the load-carrying structure in order to determine the domains of frequency of revolutions of the bucket-wheel-drive electromotor (FREM) where the dynamic response of the structure is favorable. The main goal of the presented research was the development of a unique three-step method for the identification of the FREM ranges, where the vibroactivity of the load-carrying structure is within the allowed boundaries. A methodologically original study of the dynamic response was conducted on a unique dynamic model of the BWE slewing superstructure that allows for continuous variation of the FREM, i.e., of the frequency of excitation caused by the forces resisting the excavation. Validation of the spatial reduced dynamic model of the slewing superstructure and the corresponding mathematical model, as well as the overall approach to the determination of the dynamic response, were performed by the means of vibrodiagnostics under the real exploitation conditions. Application of the developed method has yielded: (1) the resonant-free FREM domains; (2) the FREM domains, where the structure is not exposed to the excessive dynamic impacts; and (3) the frequency ratio ranges defining the resonant areas. Additionally, the results of the research have pointed out that the resonant-free state represents a necessary but insufficient condition for the proper dynamic behavior of the BWE slewing superstructure.",
publisher = "MDPI (Basel, Switzerland)",
journal = "Mathematics",
title = "Analysis of the Dynamic Response as a Basis for the Efficient Protection of Large Structure Health Using Controllable Frequency-Controlled Drives",
number = "1",
pages = "154",
volume = "11",
doi = "doi.org/10.3390/math11010154"
}

Gnjatović, N., Bošnjak, S.,& Stefanović, A. Z.. (2023). Analysis of the Dynamic Response as a Basis for the Efficient Protection of Large Structure Health Using Controllable Frequency-Controlled Drives. in Mathematics
MDPI (Basel, Switzerland)., 11(1), 154.
https://doi.org/doi.org/10.3390/math11010154

Gnjatović N, Bošnjak S, Stefanović AZ. Analysis of the Dynamic Response as a Basis for the Efficient Protection of Large Structure Health Using Controllable Frequency-Controlled Drives. in Mathematics. 2023;11(1):154.
doi:doi.org/10.3390/math11010154 .

Gnjatović, Nebojša, Bošnjak, Srđan, Stefanović, Aleksandar Z., "Analysis of the Dynamic Response as a Basis for the Efficient Protection of Large Structure Health Using Controllable Frequency-Controlled Drives" in Mathematics, 11, no. 1 (2023):154,
https://doi.org/doi.org/10.3390/math11010154 . .

TY  - CONF
AU  - Gnjatović, Nebojša
PY  - 2022
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/5342
AB  - Transfer bridges provide immense contribution to the efficient operation of high-capacity bulk material storages. The paper presents the design of one such system, used for transfering crushed gypsum and ash onto the barges docked in a storage facility, as well as the working technology, finite element strength and static stability analysis of the main substructures and the working devices. Due to the adjustments to the structure before its assembly, the analyses had to be repeated to account for the changes. Failureless operation of the presented transfer bridge represents an indirect validation of not only the presented results, but also the entire project, the stages of its development as well as the applied technology of manufacture and assembly.
PB  - SaTCIP
C3  - Proceedings of the III Maritime and Port Logistics - Bar Conference
T1  - Transfer bridge for Crushed Gypsum and Ash
EP  - 72
SP  - 67
UR  - https://hdl.handle.net/21.15107/rcub_machinery_5342
ER  - 

@conference{
author = "Gnjatović, Nebojša",
year = "2022",
abstract = "Transfer bridges provide immense contribution to the efficient operation of high-capacity bulk material storages. The paper presents the design of one such system, used for transfering crushed gypsum and ash onto the barges docked in a storage facility, as well as the working technology, finite element strength and static stability analysis of the main substructures and the working devices. Due to the adjustments to the structure before its assembly, the analyses had to be repeated to account for the changes. Failureless operation of the presented transfer bridge represents an indirect validation of not only the presented results, but also the entire project, the stages of its development as well as the applied technology of manufacture and assembly.",
publisher = "SaTCIP",
journal = "Proceedings of the III Maritime and Port Logistics - Bar Conference",
title = "Transfer bridge for Crushed Gypsum and Ash",
pages = "72-67",
url = "https://hdl.handle.net/21.15107/rcub_machinery_5342"
}

Gnjatović, N.. (2022). Transfer bridge for Crushed Gypsum and Ash. in Proceedings of the III Maritime and Port Logistics - Bar Conference
SaTCIP., 67-72.
https://hdl.handle.net/21.15107/rcub_machinery_5342

Gnjatović N. Transfer bridge for Crushed Gypsum and Ash. in Proceedings of the III Maritime and Port Logistics - Bar Conference. 2022;:67-72.
https://hdl.handle.net/21.15107/rcub_machinery_5342 .

Gnjatović, Nebojša, "Transfer bridge for Crushed Gypsum and Ash" in Proceedings of the III Maritime and Port Logistics - Bar Conference (2022):67-72,
https://hdl.handle.net/21.15107/rcub_machinery_5342 .

TY  - CONF
AU  - Gnjatović, Nebojša
AU  - Bošnjak, Srđan
AU  - Milenović, Ivan Lj.
AU  - Stefanović, Aleksandar Z.
AU  - Urošević, Marko
PY  - 2022
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/5001
AB  - Stackers-reclaimers represent the mechanization backbone of high-capacity storages for granular materials. The paper presents the design of a gantry bucket chain stackers-reclaimer for handling of crushed gypsum, as well as the working technology, finite element strength calculation for the main substructures: the working device, the trolley and the gantry. Failureless operation of the presented stacker-reclaimer represent an indirect validation of not only the presented results, but also the entire project as well as the applied technology of manufacture and montage.
PB  - University of Belgrade, Faculty of Mechanical Engineering
C3  - Proceedings of the XXIV International Conference MHCL’22
T1  - Gantry Bucket Chain Stacker- Reclaimer for Crushed Gypsum
EP  - 60
SP  - 55
UR  - https://hdl.handle.net/21.15107/rcub_machinery_5001
ER  - 

@conference{
author = "Gnjatović, Nebojša and Bošnjak, Srđan and Milenović, Ivan Lj. and Stefanović, Aleksandar Z. and Urošević, Marko",
year = "2022",
abstract = "Stackers-reclaimers represent the mechanization backbone of high-capacity storages for granular materials. The paper presents the design of a gantry bucket chain stackers-reclaimer for handling of crushed gypsum, as well as the working technology, finite element strength calculation for the main substructures: the working device, the trolley and the gantry. Failureless operation of the presented stacker-reclaimer represent an indirect validation of not only the presented results, but also the entire project as well as the applied technology of manufacture and montage.",
publisher = "University of Belgrade, Faculty of Mechanical Engineering",
journal = "Proceedings of the XXIV International Conference MHCL’22",
title = "Gantry Bucket Chain Stacker- Reclaimer for Crushed Gypsum",
pages = "60-55",
url = "https://hdl.handle.net/21.15107/rcub_machinery_5001"
}

Gnjatović, N., Bošnjak, S., Milenović, I. Lj., Stefanović, A. Z.,& Urošević, M.. (2022). Gantry Bucket Chain Stacker- Reclaimer for Crushed Gypsum. in Proceedings of the XXIV International Conference MHCL’22
University of Belgrade, Faculty of Mechanical Engineering., 55-60.
https://hdl.handle.net/21.15107/rcub_machinery_5001

Gnjatović N, Bošnjak S, Milenović IL, Stefanović AZ, Urošević M. Gantry Bucket Chain Stacker- Reclaimer for Crushed Gypsum. in Proceedings of the XXIV International Conference MHCL’22. 2022;:55-60.
https://hdl.handle.net/21.15107/rcub_machinery_5001 .

Gnjatović, Nebojša, Bošnjak, Srđan, Milenović, Ivan Lj., Stefanović, Aleksandar Z., Urošević, Marko, "Gantry Bucket Chain Stacker- Reclaimer for Crushed Gypsum" in Proceedings of the XXIV International Conference MHCL’22 (2022):55-60,
https://hdl.handle.net/21.15107/rcub_machinery_5001 .

TY  - CONF
AU  - Stefanović, Aleksandar Z.
AU  - Gnjatović, Nebojša
AU  - Milojević, Goran
AU  - Đenadić, Stevan
AU  - Urošević, Marko
PY  - 2022
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/4999
AB  - Bucket wheel excavators (BWEs) are the largest mobile terrestrial machines exposed to the working loads of a periodic character. This paper presents a small portion of the studies, conducted with the goal of proposing a new idea regarding preservation of the load-carrying
structures of these machines, based on the implementation of a controllable frequency-controlled drive of the excavating device. A detailed analysis of the dynamic response of the load-carrying structure is required in order to determine the domains of frequency of revolutions of the working device's driving motor where the dynamic response of the structure is favorable, and therefore successfully implement this idea. A methodologically-original study was conducted, using a unique dynamic model of the BWE slewing superstructure that allows for the continuous
variation of the frequency of excitation. This has yielded the resonant-free domains, i.e. the domains where the structure is not exposed to the excessive dynamic impacts.
PB  - University of Belgrade, Faculty of Mechanical Engineering
C3  - Proceedings of the XXIV International Conference MHCL’22
T1  - Analysis of the impact of the frequency-controlled bucket wheel drive on the dynamic response of the excavator superstructure
UR  - https://hdl.handle.net/21.15107/rcub_machinery_4999
ER  - 

@conference{
author = "Stefanović, Aleksandar Z. and Gnjatović, Nebojša and Milojević, Goran and Đenadić, Stevan and Urošević, Marko",
year = "2022",
abstract = "Bucket wheel excavators (BWEs) are the largest mobile terrestrial machines exposed to the working loads of a periodic character. This paper presents a small portion of the studies, conducted with the goal of proposing a new idea regarding preservation of the load-carrying
structures of these machines, based on the implementation of a controllable frequency-controlled drive of the excavating device. A detailed analysis of the dynamic response of the load-carrying structure is required in order to determine the domains of frequency of revolutions of the working device's driving motor where the dynamic response of the structure is favorable, and therefore successfully implement this idea. A methodologically-original study was conducted, using a unique dynamic model of the BWE slewing superstructure that allows for the continuous
variation of the frequency of excitation. This has yielded the resonant-free domains, i.e. the domains where the structure is not exposed to the excessive dynamic impacts.",
publisher = "University of Belgrade, Faculty of Mechanical Engineering",
journal = "Proceedings of the XXIV International Conference MHCL’22",
title = "Analysis of the impact of the frequency-controlled bucket wheel drive on the dynamic response of the excavator superstructure",
url = "https://hdl.handle.net/21.15107/rcub_machinery_4999"
}

Stefanović, A. Z., Gnjatović, N., Milojević, G., Đenadić, S.,& Urošević, M.. (2022). Analysis of the impact of the frequency-controlled bucket wheel drive on the dynamic response of the excavator superstructure. in Proceedings of the XXIV International Conference MHCL’22
University of Belgrade, Faculty of Mechanical Engineering..
https://hdl.handle.net/21.15107/rcub_machinery_4999

Stefanović AZ, Gnjatović N, Milojević G, Đenadić S, Urošević M. Analysis of the impact of the frequency-controlled bucket wheel drive on the dynamic response of the excavator superstructure. in Proceedings of the XXIV International Conference MHCL’22. 2022;.
https://hdl.handle.net/21.15107/rcub_machinery_4999 .

Stefanović, Aleksandar Z., Gnjatović, Nebojša, Milojević, Goran, Đenadić, Stevan, Urošević, Marko, "Analysis of the impact of the frequency-controlled bucket wheel drive on the dynamic response of the excavator superstructure" in Proceedings of the XXIV International Conference MHCL’22 (2022),
https://hdl.handle.net/21.15107/rcub_machinery_4999 .

TY  - GEN
AU  - Bošnjak, Srđan
AU  - Čolović, Vladan
AU  - Gnjatović, Nebojša
AU  - Milenović, Ivan Lj.
AU  - Stefanović, Aleksandar Z.
PY  - 2022
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/5046
AB  - Одлагачи, заједно са роторним багерима , припадају класи највећих копнених самоходних машина и чине окосницу система површинске експлоатације. Поменути системи представљају једно од најзначајнијих достигнућа у рударству XX века, чији је значај упоредив са значајем који је за рударе XIX века имало откриће и примена динамита.
Основни проблем који се решава применом техничког решења јесте проблем чврстоће и еластичне стабилности носеће конструкције ослоне гусенице међутранспортера одлагача (тзв. „мали транспорт“) PA 200‐2200/2000 (произвођач SANDVIK; укупна маса 1737 t; теоријски капацитет 8800 m3/h), који је у експлоатацију уведен 2016. године. У IV БТО (Багер‐Тракасти транспортер‐Одлагач) систему Површинског копа „Поље Ц“ (РБ „Колубара“) спрегнут је са роторним багером SchRs 1400 (произвођач KRUPP), теоријског капацитета 6600 m3/h. Иако је очекивани век носеће конструкције 50 година, већ након четири године експлоатације дошло је до тешке хаварије (01.07. 2020. године) носеће конструкције ослоне гусенице међутранспортера, што је праћено делимичним ослањањем на тло пријемног транспортера, као и међутранспортера. Хаварија се десила током транспорта, односно промене локације машине.
Током хаварије, најтежа оштећења доживели су елементи структуре попречног носача у зони везе са носачем круте гусенице. Са обе стране дошло је до гужвања правоугаоних вертикалних лимова и избочавања трапезних вертикалних лимова, што је праћено и пуцањем заварених веза. Истовремено, хоризонтални горњи појасни лим у потпуности је изгубио првобитну форму. Због отказа завртањске везе носача погонског мотора, дошло је до његовог пада на тло. Осим тога, код круте гусенице уочени су и ломови гусеничних чланака. Зглобна гусеница је претрпела незнатна оштећења.
Проблем који се решава техничким решењем јесте недовољна чврстоћа и еластична стабилност структуре ослоне гусенице међутранспортера одлагача савремене концепције.
Комплексност поменутог проблема проистиче из:
•	променљивости геометријске конфигурације машине, како током радног процеса, тако и
•	током транспорта;
•	релативно великог броја комбинација парцијалних оптерећења;
•	вишеструких ограничења (просторних и технолошких, пре свега) скупа могућих решења.
Осим код одлагача PA 200‐2200/2000, развијено техничко решење успешно је примењено и за парцијалну реконструкцију структуре ослоне гусенице међутранспортера одлагача PA 200‐2400/2200 (РБ „Колубара“, Површински коп „Тамнава Западно поље“, III БТО систем) истог произвођача (SANDVIK).
О значају примене техничког решења које, посебно имајући у виду актуелно стање основне рударске механизације у ЕПС‐у, изузетно доприноси стабилизацији производње откривке као предуслова за експлоатацију угља, упечатљиво говори чињеница да је у укупној производњи електричне енергије у Србији доминантно учешће (око 70% [6,7]) електричне енергије добијене из лигнита.
PB  - University of Belgrade, Faculty of Mechanical Engineering
T2  - ТЕХНИЧКО РЕШЕЊЕ (КАТЕГОРИЈА М82)
T1  - Унапређење структуре ослоне гусенице међутранспортера одлагача
UR  - https://hdl.handle.net/21.15107/rcub_machinery_5046
ER  - 

@misc{
author = "Bošnjak, Srđan and Čolović, Vladan and Gnjatović, Nebojša and Milenović, Ivan Lj. and Stefanović, Aleksandar Z.",
year = "2022",
abstract = "Одлагачи, заједно са роторним багерима , припадају класи највећих копнених самоходних машина и чине окосницу система површинске експлоатације. Поменути системи представљају једно од најзначајнијих достигнућа у рударству XX века, чији је значај упоредив са значајем који је за рударе XIX века имало откриће и примена динамита.
Основни проблем који се решава применом техничког решења јесте проблем чврстоће и еластичне стабилности носеће конструкције ослоне гусенице међутранспортера одлагача (тзв. „мали транспорт“) PA 200‐2200/2000 (произвођач SANDVIK; укупна маса 1737 t; теоријски капацитет 8800 m3/h), који је у експлоатацију уведен 2016. године. У IV БТО (Багер‐Тракасти транспортер‐Одлагач) систему Површинског копа „Поље Ц“ (РБ „Колубара“) спрегнут је са роторним багером SchRs 1400 (произвођач KRUPP), теоријског капацитета 6600 m3/h. Иако је очекивани век носеће конструкције 50 година, већ након четири године експлоатације дошло је до тешке хаварије (01.07. 2020. године) носеће конструкције ослоне гусенице међутранспортера, што је праћено делимичним ослањањем на тло пријемног транспортера, као и међутранспортера. Хаварија се десила током транспорта, односно промене локације машине.
Током хаварије, најтежа оштећења доживели су елементи структуре попречног носача у зони везе са носачем круте гусенице. Са обе стране дошло је до гужвања правоугаоних вертикалних лимова и избочавања трапезних вертикалних лимова, што је праћено и пуцањем заварених веза. Истовремено, хоризонтални горњи појасни лим у потпуности је изгубио првобитну форму. Због отказа завртањске везе носача погонског мотора, дошло је до његовог пада на тло. Осим тога, код круте гусенице уочени су и ломови гусеничних чланака. Зглобна гусеница је претрпела незнатна оштећења.
Проблем који се решава техничким решењем јесте недовољна чврстоћа и еластична стабилност структуре ослоне гусенице међутранспортера одлагача савремене концепције.
Комплексност поменутог проблема проистиче из:
•	променљивости геометријске конфигурације машине, како током радног процеса, тако и
•	током транспорта;
•	релативно великог броја комбинација парцијалних оптерећења;
•	вишеструких ограничења (просторних и технолошких, пре свега) скупа могућих решења.
Осим код одлагача PA 200‐2200/2000, развијено техничко решење успешно је примењено и за парцијалну реконструкцију структуре ослоне гусенице међутранспортера одлагача PA 200‐2400/2200 (РБ „Колубара“, Површински коп „Тамнава Западно поље“, III БТО систем) истог произвођача (SANDVIK).
О значају примене техничког решења које, посебно имајући у виду актуелно стање основне рударске механизације у ЕПС‐у, изузетно доприноси стабилизацији производње откривке као предуслова за експлоатацију угља, упечатљиво говори чињеница да је у укупној производњи електричне енергије у Србији доминантно учешће (око 70% [6,7]) електричне енергије добијене из лигнита.",
publisher = "University of Belgrade, Faculty of Mechanical Engineering",
journal = "ТЕХНИЧКО РЕШЕЊЕ (КАТЕГОРИЈА М82)",
title = "Унапређење структуре ослоне гусенице међутранспортера одлагача",
url = "https://hdl.handle.net/21.15107/rcub_machinery_5046"
}

Bošnjak, S., Čolović, V., Gnjatović, N., Milenović, I. Lj.,& Stefanović, A. Z.. (2022). Унапређење структуре ослоне гусенице међутранспортера одлагача. in ТЕХНИЧКО РЕШЕЊЕ (КАТЕГОРИЈА М82)
University of Belgrade, Faculty of Mechanical Engineering..
https://hdl.handle.net/21.15107/rcub_machinery_5046

Bošnjak S, Čolović V, Gnjatović N, Milenović IL, Stefanović AZ. Унапређење структуре ослоне гусенице међутранспортера одлагача. in ТЕХНИЧКО РЕШЕЊЕ (КАТЕГОРИЈА М82). 2022;.
https://hdl.handle.net/21.15107/rcub_machinery_5046 .

Bošnjak, Srđan, Čolović, Vladan, Gnjatović, Nebojša, Milenović, Ivan Lj., Stefanović, Aleksandar Z., "Унапређење структуре ослоне гусенице међутранспортера одлагача" in ТЕХНИЧКО РЕШЕЊЕ (КАТЕГОРИЈА М82) (2022),
https://hdl.handle.net/21.15107/rcub_machinery_5046 .

TY  - JOUR
AU  - Milenović, Ivan Lj.
AU  - Bošnjak, Srđan
AU  - Gnjatović, Nebojša
AU  - Obradović, Aleksandar
PY  - 2022
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/3732
AB  - Identification of the basic parameters of static stability (BPSS) of the slewing superstructure is the key step in solving the problem of its static stability, as well as static stability of the entire bucket wheel excavator (BWE). Specificity of the slewing superstructure examined in this paper lies in the kinematic breakdown system (KBS) which prevents the loss of static stability on the counterweight side. Development of a unique method for the formation and two-step validation of the calculation models for this particular design concept was the main objective of the presented research. A two-step validation of the analytical models is conducted based on the experimental results. As the outcome, the final calculation model formed in such manner represents an accurate basis both for the proof of static stability and for the monitoring of the BPSS during exploitation. By comparing the results of the control weighing and the referent values of the final calculation model it was concluded that the existing double-walled bucket wheel represents a 'weak point' of the considered BWE.
PB  - Polish Maintenance Soc, Lublin
T2  - Eksploatacja I Niezawodnosc-Maintenance and Reliability
T1  - Bucket wheel excavators with a kinematic breakdown system: Identification and monitoring of the basic parameters of static stability of the slewing superstructure
EP  - 370
IS  - 2
SP  - 359
VL  - 24
DO  - 10.17531/ein.2022.2.17
ER  - 

@article{
author = "Milenović, Ivan Lj. and Bošnjak, Srđan and Gnjatović, Nebojša and Obradović, Aleksandar",
year = "2022",
abstract = "Identification of the basic parameters of static stability (BPSS) of the slewing superstructure is the key step in solving the problem of its static stability, as well as static stability of the entire bucket wheel excavator (BWE). Specificity of the slewing superstructure examined in this paper lies in the kinematic breakdown system (KBS) which prevents the loss of static stability on the counterweight side. Development of a unique method for the formation and two-step validation of the calculation models for this particular design concept was the main objective of the presented research. A two-step validation of the analytical models is conducted based on the experimental results. As the outcome, the final calculation model formed in such manner represents an accurate basis both for the proof of static stability and for the monitoring of the BPSS during exploitation. By comparing the results of the control weighing and the referent values of the final calculation model it was concluded that the existing double-walled bucket wheel represents a 'weak point' of the considered BWE.",
publisher = "Polish Maintenance Soc, Lublin",
journal = "Eksploatacja I Niezawodnosc-Maintenance and Reliability",
title = "Bucket wheel excavators with a kinematic breakdown system: Identification and monitoring of the basic parameters of static stability of the slewing superstructure",
pages = "370-359",
number = "2",
volume = "24",
doi = "10.17531/ein.2022.2.17"
}

Milenović, I. Lj., Bošnjak, S., Gnjatović, N.,& Obradović, A.. (2022). Bucket wheel excavators with a kinematic breakdown system: Identification and monitoring of the basic parameters of static stability of the slewing superstructure. in Eksploatacja I Niezawodnosc-Maintenance and Reliability
Polish Maintenance Soc, Lublin., 24(2), 359-370.
https://doi.org/10.17531/ein.2022.2.17

Milenović IL, Bošnjak S, Gnjatović N, Obradović A. Bucket wheel excavators with a kinematic breakdown system: Identification and monitoring of the basic parameters of static stability of the slewing superstructure. in Eksploatacja I Niezawodnosc-Maintenance and Reliability. 2022;24(2):359-370.
doi:10.17531/ein.2022.2.17 .

Milenović, Ivan Lj., Bošnjak, Srđan, Gnjatović, Nebojša, Obradović, Aleksandar, "Bucket wheel excavators with a kinematic breakdown system: Identification and monitoring of the basic parameters of static stability of the slewing superstructure" in Eksploatacja I Niezawodnosc-Maintenance and Reliability, 24, no. 2 (2022):359-370,
https://doi.org/10.17531/ein.2022.2.17 . .

TY  - JOUR
AU  - Bošnjak, Srđan
AU  - Zrnić, Nenad
AU  - Momčilović, Dejan B.
AU  - Gnjatović, Nebojša
AU  - Milenović, Ivan Lj.
PY  - 2020
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/3400
AB  - Tie-rods of the bucket wheel and counterweight booms are vital parts of the bucket wheel excavator slewing superstructure. This paper is dedicated to the problem of identifying the stress state of the critical cross-section ('net section') of the eye plates on these tie-rods. It presents the results of the experimental and numerical investigations carried out on the eyebar model. The results show the appearance of a plastic deformation in the zone near the contour of the hole even when the eye is subjected to the loads within the range of the permissible loads prescribed by the standard DIN 22261-2. Plastification in the eye net section occurs across the full thickness of the plate, but it does not jeopardize the integrity of the structure. The stress value in the eye net section, calculated in accordance with the standard DIN 22261-2, is significantly lower than the actual stress values around the hole and serves only as a comparative value for the static strength proof for the eye.
PB  - Elsevier Sci Ltd, Oxford
T2  - Engineering Structures
T1  - Tie-rods of the bucket wheel excavator slewing superstructure: A study of the eye plate stress state
VL  - 207
DO  - 10.1016/j.engstruct.2020.110233
ER  - 

@article{
author = "Bošnjak, Srđan and Zrnić, Nenad and Momčilović, Dejan B. and Gnjatović, Nebojša and Milenović, Ivan Lj.",
year = "2020",
abstract = "Tie-rods of the bucket wheel and counterweight booms are vital parts of the bucket wheel excavator slewing superstructure. This paper is dedicated to the problem of identifying the stress state of the critical cross-section ('net section') of the eye plates on these tie-rods. It presents the results of the experimental and numerical investigations carried out on the eyebar model. The results show the appearance of a plastic deformation in the zone near the contour of the hole even when the eye is subjected to the loads within the range of the permissible loads prescribed by the standard DIN 22261-2. Plastification in the eye net section occurs across the full thickness of the plate, but it does not jeopardize the integrity of the structure. The stress value in the eye net section, calculated in accordance with the standard DIN 22261-2, is significantly lower than the actual stress values around the hole and serves only as a comparative value for the static strength proof for the eye.",
publisher = "Elsevier Sci Ltd, Oxford",
journal = "Engineering Structures",
title = "Tie-rods of the bucket wheel excavator slewing superstructure: A study of the eye plate stress state",
volume = "207",
doi = "10.1016/j.engstruct.2020.110233"
}

Bošnjak, S., Zrnić, N., Momčilović, D. B., Gnjatović, N.,& Milenović, I. Lj.. (2020). Tie-rods of the bucket wheel excavator slewing superstructure: A study of the eye plate stress state. in Engineering Structures
Elsevier Sci Ltd, Oxford., 207.
https://doi.org/10.1016/j.engstruct.2020.110233

Bošnjak S, Zrnić N, Momčilović DB, Gnjatović N, Milenović IL. Tie-rods of the bucket wheel excavator slewing superstructure: A study of the eye plate stress state. in Engineering Structures. 2020;207.
doi:10.1016/j.engstruct.2020.110233 .

Bošnjak, Srđan, Zrnić, Nenad, Momčilović, Dejan B., Gnjatović, Nebojša, Milenović, Ivan Lj., "Tie-rods of the bucket wheel excavator slewing superstructure: A study of the eye plate stress state" in Engineering Structures, 207 (2020),
https://doi.org/10.1016/j.engstruct.2020.110233 . .

TY  - CONF
AU  - Bošnjak, Srđan
AU  - Gnjatović, Nebojša
AU  - Stefanović, Aleksandar Z.
AU  - Milenović, Ivan Lj.
PY  - 2020
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/4940
AB  - The design concept of temporary leaning of the gas oil storage tank bearing structure used during substitution of the worn out section of the bottom plates in the zone of the central column support is presented in the paper. On the basis of comparative analysis of the results obtained using finite element structural calculations of the designed state and the state of the central column leaning on the temporary supports, it was determined that by the implementation of the temporary support, the stress-strain state of the bearing structure, which corresponds to the designed stress-strain state of the construction, is obtained. Besides, the strength proof of the structure of temporary support including its welded joint to the central column is also presented in the paper.
PB  - SaTCIP
C3  - 20th International Conference "Research and Development in Mechanical Industry" RaDMI-2020
T1  - Temporary Leaning of the Gas Oil Storage Tank Structure During Bottom Sanation
EP  - 10
SP  - 1
UR  - https://hdl.handle.net/21.15107/rcub_machinery_4940
ER  - 

@conference{
author = "Bošnjak, Srđan and Gnjatović, Nebojša and Stefanović, Aleksandar Z. and Milenović, Ivan Lj.",
year = "2020",
abstract = "The design concept of temporary leaning of the gas oil storage tank bearing structure used during substitution of the worn out section of the bottom plates in the zone of the central column support is presented in the paper. On the basis of comparative analysis of the results obtained using finite element structural calculations of the designed state and the state of the central column leaning on the temporary supports, it was determined that by the implementation of the temporary support, the stress-strain state of the bearing structure, which corresponds to the designed stress-strain state of the construction, is obtained. Besides, the strength proof of the structure of temporary support including its welded joint to the central column is also presented in the paper.",
publisher = "SaTCIP",
journal = "20th International Conference "Research and Development in Mechanical Industry" RaDMI-2020",
title = "Temporary Leaning of the Gas Oil Storage Tank Structure During Bottom Sanation",
pages = "10-1",
url = "https://hdl.handle.net/21.15107/rcub_machinery_4940"
}

Bošnjak, S., Gnjatović, N., Stefanović, A. Z.,& Milenović, I. Lj.. (2020). Temporary Leaning of the Gas Oil Storage Tank Structure During Bottom Sanation. in 20th International Conference "Research and Development in Mechanical Industry" RaDMI-2020
SaTCIP., 1-10.
https://hdl.handle.net/21.15107/rcub_machinery_4940

Bošnjak S, Gnjatović N, Stefanović AZ, Milenović IL. Temporary Leaning of the Gas Oil Storage Tank Structure During Bottom Sanation. in 20th International Conference "Research and Development in Mechanical Industry" RaDMI-2020. 2020;:1-10.
https://hdl.handle.net/21.15107/rcub_machinery_4940 .

Bošnjak, Srđan, Gnjatović, Nebojša, Stefanović, Aleksandar Z., Milenović, Ivan Lj., "Temporary Leaning of the Gas Oil Storage Tank Structure During Bottom Sanation" in 20th International Conference "Research and Development in Mechanical Industry" RaDMI-2020 (2020):1-10,
https://hdl.handle.net/21.15107/rcub_machinery_4940 .

TY  - CONF
AU  - Bošnjak, Srđan
AU  - Gnjatović, Nebojša
PY  - 2020
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/4939
AB  - A slewing superstructure (SS) represents a key functional subsystem of bucket wheel excavators (BWEs). Identification of its basic parameters of static stability (BPSS: weight and position of the center of gravity) is of equally crucial significance in design of a BWE and in its exploitation. The BPSS dominantly determine the static stability of a BWE SS and, coupled with stiffness, its
dynamic response. This paper presents the results of research on the impact of the difference between the experimentally and analytically determined SS BPSS on the: (1) intensities of forces in the ropes of the bucket wheel boom hoisting mechanism; (2) maximum loads of the SS radiaxial slew bearing balls; (3) dynamic response of the SS. The presented research represents the initial stage in forming of the integral methodology for the assessment of impact of the mentioned differences on the key indicators which determine the lifespan and integrity, as well as reliability and safety of the SS of BWEs and related surface mining and material handling machines.
PB  - Faculty of Mechanical Engineering in Niš
C3  - Proceedings of the fifth international conference “Mechanical Engineering in XXI Century” MASING 2020
T1  - Bucket Wheel Excavators: Balancing and Dynamic Response of the Slewing Superstructure
EP  - 26
SP  - 9
UR  - https://hdl.handle.net/21.15107/rcub_machinery_4939
ER  - 

@conference{
author = "Bošnjak, Srđan and Gnjatović, Nebojša",
year = "2020",
abstract = "A slewing superstructure (SS) represents a key functional subsystem of bucket wheel excavators (BWEs). Identification of its basic parameters of static stability (BPSS: weight and position of the center of gravity) is of equally crucial significance in design of a BWE and in its exploitation. The BPSS dominantly determine the static stability of a BWE SS and, coupled with stiffness, its
dynamic response. This paper presents the results of research on the impact of the difference between the experimentally and analytically determined SS BPSS on the: (1) intensities of forces in the ropes of the bucket wheel boom hoisting mechanism; (2) maximum loads of the SS radiaxial slew bearing balls; (3) dynamic response of the SS. The presented research represents the initial stage in forming of the integral methodology for the assessment of impact of the mentioned differences on the key indicators which determine the lifespan and integrity, as well as reliability and safety of the SS of BWEs and related surface mining and material handling machines.",
publisher = "Faculty of Mechanical Engineering in Niš",
journal = "Proceedings of the fifth international conference “Mechanical Engineering in XXI Century” MASING 2020",
title = "Bucket Wheel Excavators: Balancing and Dynamic Response of the Slewing Superstructure",
pages = "26-9",
url = "https://hdl.handle.net/21.15107/rcub_machinery_4939"
}

Bošnjak, S.,& Gnjatović, N.. (2020). Bucket Wheel Excavators: Balancing and Dynamic Response of the Slewing Superstructure. in Proceedings of the fifth international conference “Mechanical Engineering in XXI Century” MASING 2020
Faculty of Mechanical Engineering in Niš., 9-26.
https://hdl.handle.net/21.15107/rcub_machinery_4939

Bošnjak S, Gnjatović N. Bucket Wheel Excavators: Balancing and Dynamic Response of the Slewing Superstructure. in Proceedings of the fifth international conference “Mechanical Engineering in XXI Century” MASING 2020. 2020;:9-26.
https://hdl.handle.net/21.15107/rcub_machinery_4939 .

Bošnjak, Srđan, Gnjatović, Nebojša, "Bucket Wheel Excavators: Balancing and Dynamic Response of the Slewing Superstructure" in Proceedings of the fifth international conference “Mechanical Engineering in XXI Century” MASING 2020 (2020):9-26,
https://hdl.handle.net/21.15107/rcub_machinery_4939 .

TY  - GEN
AU  - Bošnjak, Srđan
AU  - Pantelić, Milorad
AU  - Misita, Mirjana
AU  - Gnjatović, Nebojša
AU  - Stefanović, Aleksandar Z.
PY  - 2020
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/5042
AB  - Последице отказа свих висококапацитетних машина јесу врло велики финансијски губици и озбиљни ризици по сигурност и здравље. Када је реч о багерским јединицама, финансијски губици изазвани застојем производње због отказа основне машине у систему површинске експлоатације, односно складиштења и отпреме угља, најчешће знатно превазилазе финансијске губитке изазване директном материјалном штетом, зависно од њиховог капацитета и врсте материјала који се откопава (угаљ или јаловина) [1‐5]. О величини негативних економских ефеката изазваних отказима/хаваријама упечатљиво говори податак да у САД и Европској унији укупни трошак изазван отказима машина и система износи приближно 4% од БНП [6].
Примена техничког решења омогућава решавање следећих проблема:
•	подизање нивоа одржавања, ефективности, поузданости и сигурности роторних багера, односно БТО/Д/У система;
•	подизање нивоа економичности експлоатације БТО/Д/У система; чиме се вишетрукуко смањују ризици током експлоатације и одржавања багерских јединица.
Осим тога, применом техничког решења стварају се основе за:
•	управљање поузданошћу и сигурношћу БТО/Д/У система;
•	испуњавање критеријума ригорозне регулативе везане за заштиту животне средине и сигурност руковалаца и одржавалаца.
На значај примене техничког решења у термоенергетици Србије упућују следећечињенице:
•	највећи произвођачи елекричне енергије у Србији су термоелектране. Према [7], 2014. године 65,1% електричне енергије у Србији произведено је из лигнита, док је у 2015. години 70,3 % електричне енергије добијено из поменутог извора;
•	РБ „Колубара“ даје ≈75% производње лигнита у Србији [7];
•	у цени електричне енергије угаљ учествује са ≈60%;
•	одржавање механизације на површинским коповима учествује са 35‐40% у цени угља;
•	у односу на пројектовани номинални век (35‐40 година), просечне старости машина (31,6 год. багера за континуални ископ, 31,1 год. одлагача и самоходних транспортера) и њихових капацитета (28,3 год. багера за континуални ископ, 27,2 год. одлагача и самоходних транспортера) у РБ „Колубара“, врло су високе;
•	сат застоја БТО/Д/У у РБ „Колубара“ нормира се као индиректна материјална штета у износу од 5000‐15000 €, зависно од капацитета машине, односно материјала који се откопава/транспортује.
PB  - University of Belgrade, Faculty of Mechanical Engineering
T2  - ТЕХНИЧКО РЕШЕЊЕ (КАТЕГОРИЈА М82)
T1  - Минимизација ризика у експлоатацији и одржавању роторних багера
UR  - https://hdl.handle.net/21.15107/rcub_machinery_5042
ER  - 

@misc{
author = "Bošnjak, Srđan and Pantelić, Milorad and Misita, Mirjana and Gnjatović, Nebojša and Stefanović, Aleksandar Z.",
year = "2020",
abstract = "Последице отказа свих висококапацитетних машина јесу врло велики финансијски губици и озбиљни ризици по сигурност и здравље. Када је реч о багерским јединицама, финансијски губици изазвани застојем производње због отказа основне машине у систему површинске експлоатације, односно складиштења и отпреме угља, најчешће знатно превазилазе финансијске губитке изазване директном материјалном штетом, зависно од њиховог капацитета и врсте материјала који се откопава (угаљ или јаловина) [1‐5]. О величини негативних економских ефеката изазваних отказима/хаваријама упечатљиво говори податак да у САД и Европској унији укупни трошак изазван отказима машина и система износи приближно 4% од БНП [6].
Примена техничког решења омогућава решавање следећих проблема:
•	подизање нивоа одржавања, ефективности, поузданости и сигурности роторних багера, односно БТО/Д/У система;
•	подизање нивоа економичности експлоатације БТО/Д/У система; чиме се вишетрукуко смањују ризици током експлоатације и одржавања багерских јединица.
Осим тога, применом техничког решења стварају се основе за:
•	управљање поузданошћу и сигурношћу БТО/Д/У система;
•	испуњавање критеријума ригорозне регулативе везане за заштиту животне средине и сигурност руковалаца и одржавалаца.
На значај примене техничког решења у термоенергетици Србије упућују следећечињенице:
•	највећи произвођачи елекричне енергије у Србији су термоелектране. Према [7], 2014. године 65,1% електричне енергије у Србији произведено је из лигнита, док је у 2015. години 70,3 % електричне енергије добијено из поменутог извора;
•	РБ „Колубара“ даје ≈75% производње лигнита у Србији [7];
•	у цени електричне енергије угаљ учествује са ≈60%;
•	одржавање механизације на површинским коповима учествује са 35‐40% у цени угља;
•	у односу на пројектовани номинални век (35‐40 година), просечне старости машина (31,6 год. багера за континуални ископ, 31,1 год. одлагача и самоходних транспортера) и њихових капацитета (28,3 год. багера за континуални ископ, 27,2 год. одлагача и самоходних транспортера) у РБ „Колубара“, врло су високе;
•	сат застоја БТО/Д/У у РБ „Колубара“ нормира се као индиректна материјална штета у износу од 5000‐15000 €, зависно од капацитета машине, односно материјала који се откопава/транспортује.",
publisher = "University of Belgrade, Faculty of Mechanical Engineering",
journal = "ТЕХНИЧКО РЕШЕЊЕ (КАТЕГОРИЈА М82)",
title = "Минимизација ризика у експлоатацији и одржавању роторних багера",
url = "https://hdl.handle.net/21.15107/rcub_machinery_5042"
}

Bošnjak, S., Pantelić, M., Misita, M., Gnjatović, N.,& Stefanović, A. Z.. (2020). Минимизација ризика у експлоатацији и одржавању роторних багера. in ТЕХНИЧКО РЕШЕЊЕ (КАТЕГОРИЈА М82)
University of Belgrade, Faculty of Mechanical Engineering..
https://hdl.handle.net/21.15107/rcub_machinery_5042

Bošnjak S, Pantelić M, Misita M, Gnjatović N, Stefanović AZ. Минимизација ризика у експлоатацији и одржавању роторних багера. in ТЕХНИЧКО РЕШЕЊЕ (КАТЕГОРИЈА М82). 2020;.
https://hdl.handle.net/21.15107/rcub_machinery_5042 .

Bošnjak, Srđan, Pantelić, Milorad, Misita, Mirjana, Gnjatović, Nebojša, Stefanović, Aleksandar Z., "Минимизација ризика у експлоатацији и одржавању роторних багера" in ТЕХНИЧКО РЕШЕЊЕ (КАТЕГОРИЈА М82) (2020),
https://hdl.handle.net/21.15107/rcub_machinery_5042 .

TY  - GEN
AU  - Bošnjak, Srđan
AU  - Gnjatović, Nebojša
AU  - Milenović, Ivan Lj.
PY  - 2020
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/5041
AB  - Одговор на питање „шта радити након вагања горње градње?“ дат је једино у [7] (страна 233): „Уколико се резултати вагања разликују за више од 5% од теоријских‐прорачунских вредности усвојених за анализу стабилности, мора се проверити прорачун и поновити процедура вагања. Након тога, мора се извршити корекција баласта тако да положај тежишта одговара прорачунским вредностима.“ Дакле, одговор је начелног карактера, уз напомену да су масе обртне горње градње код роторних багера средње величине (класе), који доминирају на српским угљенокопима око 1000 t, при чему се пројектоване масе баласта крећу у распону од 175 t (роторни багер SRs 2000) до 500 t (роторни багер SchRs 1760).
С обзиром на изузетан значај проблема статичке стабилности, техничким решењем уведена је класификација модела обртне горње градње у две основне групе, модели 'а приори' и модели 'а постериори' и дат поступак трансформације прорачунског модела 'а приори' (пројектована слика обртне горње градње) у прорачунски модел 'а постериори' (стварна слика обртне градње). Основне фазе нове методе прорачуна статичке стабилности обртне горње градње ('а постериори') су:
1.	усклађивање прорачунског модела са свим изменама насталим током развоја пројекта и извођења монтаже, односно формирање прорачунског модела 'а приори';
2.	прво вагање, непосредно након завршене монтаже;
3.	израчунавање тежине и положаја тежишта модела 'а приори' за мерне положаје стреле ротора;
4.	израчунавање корективне масе, као и њеног положаја, на основу резултата првог мерења;
5.	формирање прорачунског модела 'а постериори' узимајући у обзир и утицај корективне масе;
6.	валидација прорачунског модела 'а постериори' на основу резултата првог мерења;
7.	одређивање потребне корекције масе противтега и подешених вредности сила у ужадима механизма за промену угла нагиба стреле ротора, на основу резултата прорачуна стабилности изведених на моделу 'а постериори';
8.	друго (контролно) мерење са коригованом масом противтега;
9.	израчунавање тежине и положаја тежишта модела 'а постериори' за положаје стреле ротора током мерења 2;
10.	коначна валидација модела 'а постериори' на основу резултата другог мерења;
11.	коначни прорачун минималних вредности степена сигурности против претурања, на целокупном домену угла нагиба стреле ротора, коришћењем модела 'а постериори'. 
	Модели 'а постериори' од изузетне су важности и за успешну и поуздану експлоатацију машине зато што представљају основу за:
•	подешавање и контролу граничних вредности сила у ужадима механизма за промену угла нагиба стреле ротора;
•	периодичну контролу тежине и положаја тежишта;
•	евентуалне реконструкције са циљем да се оствари оптимално прилагођавање машине условима рада;
што је посебно значајно због чињенице да су роторни багери и одлагачи машине намењене за вишедеценијску експлоатацију.
Коначно, суштину техничког решења, уз детаљан приказ механичког и математичког модела, аутори су 2018. године публиковали у часопису Eksploatacja i Niezawodnosc – Maintenance and Reliability (категорија М22, IF2018=1.806), као рад под називом „From ‘a priori’ to ‘a posteriori’ static stability of the slewing superstructure of a bucket wheel excavator“, Прилог 3 (http://dx.doi.org/10.17531/ein.2018.2.04). Наведени рад представља први рад из области статичке стабилности роторних багера и сродних машина објављен у часопису са SCI листе, што доказује научни потенцијал техничког решења.
PB  - University of Belgrade, Faculty of Mechanical Engineering
T2  - ТЕХНИЧКО РЕШЕЊЕ (КАТЕГОРИЈА М82)
T1  - Од а приори до а постериори статичке стабилности роторних багера
UR  - https://hdl.handle.net/21.15107/rcub_machinery_5041
ER  - 

@misc{
author = "Bošnjak, Srđan and Gnjatović, Nebojša and Milenović, Ivan Lj.",
year = "2020",
abstract = "Одговор на питање „шта радити након вагања горње градње?“ дат је једино у [7] (страна 233): „Уколико се резултати вагања разликују за више од 5% од теоријских‐прорачунских вредности усвојених за анализу стабилности, мора се проверити прорачун и поновити процедура вагања. Након тога, мора се извршити корекција баласта тако да положај тежишта одговара прорачунским вредностима.“ Дакле, одговор је начелног карактера, уз напомену да су масе обртне горње градње код роторних багера средње величине (класе), који доминирају на српским угљенокопима око 1000 t, при чему се пројектоване масе баласта крећу у распону од 175 t (роторни багер SRs 2000) до 500 t (роторни багер SchRs 1760).
С обзиром на изузетан значај проблема статичке стабилности, техничким решењем уведена је класификација модела обртне горње градње у две основне групе, модели 'а приори' и модели 'а постериори' и дат поступак трансформације прорачунског модела 'а приори' (пројектована слика обртне горње градње) у прорачунски модел 'а постериори' (стварна слика обртне градње). Основне фазе нове методе прорачуна статичке стабилности обртне горње градње ('а постериори') су:
1.	усклађивање прорачунског модела са свим изменама насталим током развоја пројекта и извођења монтаже, односно формирање прорачунског модела 'а приори';
2.	прво вагање, непосредно након завршене монтаже;
3.	израчунавање тежине и положаја тежишта модела 'а приори' за мерне положаје стреле ротора;
4.	израчунавање корективне масе, као и њеног положаја, на основу резултата првог мерења;
5.	формирање прорачунског модела 'а постериори' узимајући у обзир и утицај корективне масе;
6.	валидација прорачунског модела 'а постериори' на основу резултата првог мерења;
7.	одређивање потребне корекције масе противтега и подешених вредности сила у ужадима механизма за промену угла нагиба стреле ротора, на основу резултата прорачуна стабилности изведених на моделу 'а постериори';
8.	друго (контролно) мерење са коригованом масом противтега;
9.	израчунавање тежине и положаја тежишта модела 'а постериори' за положаје стреле ротора током мерења 2;
10.	коначна валидација модела 'а постериори' на основу резултата другог мерења;
11.	коначни прорачун минималних вредности степена сигурности против претурања, на целокупном домену угла нагиба стреле ротора, коришћењем модела 'а постериори'. 
	Модели 'а постериори' од изузетне су важности и за успешну и поуздану експлоатацију машине зато што представљају основу за:
•	подешавање и контролу граничних вредности сила у ужадима механизма за промену угла нагиба стреле ротора;
•	периодичну контролу тежине и положаја тежишта;
•	евентуалне реконструкције са циљем да се оствари оптимално прилагођавање машине условима рада;
што је посебно значајно због чињенице да су роторни багери и одлагачи машине намењене за вишедеценијску експлоатацију.
Коначно, суштину техничког решења, уз детаљан приказ механичког и математичког модела, аутори су 2018. године публиковали у часопису Eksploatacja i Niezawodnosc – Maintenance and Reliability (категорија М22, IF2018=1.806), као рад под називом „From ‘a priori’ to ‘a posteriori’ static stability of the slewing superstructure of a bucket wheel excavator“, Прилог 3 (http://dx.doi.org/10.17531/ein.2018.2.04). Наведени рад представља први рад из области статичке стабилности роторних багера и сродних машина објављен у часопису са SCI листе, што доказује научни потенцијал техничког решења.",
publisher = "University of Belgrade, Faculty of Mechanical Engineering",
journal = "ТЕХНИЧКО РЕШЕЊЕ (КАТЕГОРИЈА М82)",
title = "Од а приори до а постериори статичке стабилности роторних багера",
url = "https://hdl.handle.net/21.15107/rcub_machinery_5041"
}

Bošnjak, S., Gnjatović, N.,& Milenović, I. Lj.. (2020). Од а приори до а постериори статичке стабилности роторних багера. in ТЕХНИЧКО РЕШЕЊЕ (КАТЕГОРИЈА М82)
University of Belgrade, Faculty of Mechanical Engineering..
https://hdl.handle.net/21.15107/rcub_machinery_5041

Bošnjak S, Gnjatović N, Milenović IL. Од а приори до а постериори статичке стабилности роторних багера. in ТЕХНИЧКО РЕШЕЊЕ (КАТЕГОРИЈА М82). 2020;.
https://hdl.handle.net/21.15107/rcub_machinery_5041 .

Bošnjak, Srđan, Gnjatović, Nebojša, Milenović, Ivan Lj., "Од а приори до а постериори статичке стабилности роторних багера" in ТЕХНИЧКО РЕШЕЊЕ (КАТЕГОРИЈА М82) (2020),
https://hdl.handle.net/21.15107/rcub_machinery_5041 .

TY  - JOUR
AU  - Pantelić, Milorad P.
AU  - Bošnjak, Srđan
AU  - Misita, Mirjana
AU  - Gnjatović, Nebojša
AU  - Stefanović, Aleksandar Z.
PY  - 2020
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/3285
AB  - Surface mining systems (SMSs) are among the most significant 20th century achievements in mining industry, whose significance to miners is comparable to the invention of dynamite in the 19th century. However, problems of SMS risk assessment are very scarce in relevant literature. For this reason, this paper aims to establish a consistent risk quantification approach for bucket wheel excavators (BWEs), the backbones of these systems. Based on the original structural scheme of a BWE, the risk parameters assessing criteria stemming from multidecadal experience and the database of recorded standstills (in the considered case, one hour of SMS downtime generates indirect financial losses of approximate to 15000(sic)), a study was conducted applying the Service FMECA technique to the BWE SRs2000 (one of the best-selling models from "Takraf"), with the following conclusions: (a) the material conveying subsystem is the highest contributor in the total number of mechanical and electrical failures, as well as in total downtime; (b) during the monitoring period, there were no extreme risk level failures. Besides, corrective actions for reducing risk levels of the most critical mechanical and electrical failure modes are given in the paper. The presented approach for risk quantification for a BWE can be successfully applied to other SMS subsystems, notably spreaders.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Engineering Failure Analysis
T1  - Service FMECA of a bucket wheel excavator
VL  - 108
DO  - 10.1016/j.engfailanal.2019.104289
ER  - 

@article{
author = "Pantelić, Milorad P. and Bošnjak, Srđan and Misita, Mirjana and Gnjatović, Nebojša and Stefanović, Aleksandar Z.",
year = "2020",
abstract = "Surface mining systems (SMSs) are among the most significant 20th century achievements in mining industry, whose significance to miners is comparable to the invention of dynamite in the 19th century. However, problems of SMS risk assessment are very scarce in relevant literature. For this reason, this paper aims to establish a consistent risk quantification approach for bucket wheel excavators (BWEs), the backbones of these systems. Based on the original structural scheme of a BWE, the risk parameters assessing criteria stemming from multidecadal experience and the database of recorded standstills (in the considered case, one hour of SMS downtime generates indirect financial losses of approximate to 15000(sic)), a study was conducted applying the Service FMECA technique to the BWE SRs2000 (one of the best-selling models from "Takraf"), with the following conclusions: (a) the material conveying subsystem is the highest contributor in the total number of mechanical and electrical failures, as well as in total downtime; (b) during the monitoring period, there were no extreme risk level failures. Besides, corrective actions for reducing risk levels of the most critical mechanical and electrical failure modes are given in the paper. The presented approach for risk quantification for a BWE can be successfully applied to other SMS subsystems, notably spreaders.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Engineering Failure Analysis",
title = "Service FMECA of a bucket wheel excavator",
volume = "108",
doi = "10.1016/j.engfailanal.2019.104289"
}

Pantelić, M. P., Bošnjak, S., Misita, M., Gnjatović, N.,& Stefanović, A. Z.. (2020). Service FMECA of a bucket wheel excavator. in Engineering Failure Analysis
Pergamon-Elsevier Science Ltd, Oxford., 108.
https://doi.org/10.1016/j.engfailanal.2019.104289

Pantelić MP, Bošnjak S, Misita M, Gnjatović N, Stefanović AZ. Service FMECA of a bucket wheel excavator. in Engineering Failure Analysis. 2020;108.
doi:10.1016/j.engfailanal.2019.104289 .

Pantelić, Milorad P., Bošnjak, Srđan, Misita, Mirjana, Gnjatović, Nebojša, Stefanović, Aleksandar Z., "Service FMECA of a bucket wheel excavator" in Engineering Failure Analysis, 108 (2020),
https://doi.org/10.1016/j.engfailanal.2019.104289 . .

TY  - JOUR
AU  - Gnjatović, Nebojša
AU  - Bošnjak, Srđan
AU  - Milenović, Ivan Lj.
AU  - Stefanović, Aleksandar Z.
PY  - 2020
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/3337
AB  - An original method for validation of the number of buckets on the working device of a bucket wheel excavator based on the dynamic response of its slewing superstructure (SS) is presented. A set of 16 seemingly acceptable solutions which satisfied the rigid design restrictions, based on the preservation of the existing (a) bucket wheel drivetrain, (b) theoretical capacity, (c) characteristics of the excavated soil and (d) position of the superstructure centre of gravity (CoG), was analysed. Already on the basis of the limiting vertical and lateral accelerations of the bucket wheel centre, which represents a well-grounded indicator of its dynamic behaviour prescribed by the code DIN 22261-2, 14 out of 16 analysed design variants have been discarded, reducing the set of possible solutions to only two - the originally-designed variant (with 17 buckets), and the variant with 20 buckets. Conclusions on the validity of these two design variants were derived on the basis of the dynamic response analysis of the referent points of the SS. The analysis of the impact of soiling on the dynamic response of the SS has shown that negative dynamic effects, observed in the preceding analysis of the originally-designed solution, increase with the amount of the adhered material. Although the redesigned variant with 20 buckets has proven as the only suitable solution from the standpoint of dynamic behaviour of the SS, the results have to be assessed carefully due to the fact that the reduction of the mass of the bucket wheel steel structure by more than 14% leads to the appearance of unfavourable dynamic effects, even though the SS CoG position is preserved.
PB  - Elsevier Sci Ltd, Oxford
T2  - Engineering Structures
T1  - Bucket wheel excavators: Dynamic response as a criterion for validation of the total number of buckets
VL  - 225
DO  - 10.1016/j.engstruct.2020.111313
ER  - 

@article{
author = "Gnjatović, Nebojša and Bošnjak, Srđan and Milenović, Ivan Lj. and Stefanović, Aleksandar Z.",
year = "2020",
abstract = "An original method for validation of the number of buckets on the working device of a bucket wheel excavator based on the dynamic response of its slewing superstructure (SS) is presented. A set of 16 seemingly acceptable solutions which satisfied the rigid design restrictions, based on the preservation of the existing (a) bucket wheel drivetrain, (b) theoretical capacity, (c) characteristics of the excavated soil and (d) position of the superstructure centre of gravity (CoG), was analysed. Already on the basis of the limiting vertical and lateral accelerations of the bucket wheel centre, which represents a well-grounded indicator of its dynamic behaviour prescribed by the code DIN 22261-2, 14 out of 16 analysed design variants have been discarded, reducing the set of possible solutions to only two - the originally-designed variant (with 17 buckets), and the variant with 20 buckets. Conclusions on the validity of these two design variants were derived on the basis of the dynamic response analysis of the referent points of the SS. The analysis of the impact of soiling on the dynamic response of the SS has shown that negative dynamic effects, observed in the preceding analysis of the originally-designed solution, increase with the amount of the adhered material. Although the redesigned variant with 20 buckets has proven as the only suitable solution from the standpoint of dynamic behaviour of the SS, the results have to be assessed carefully due to the fact that the reduction of the mass of the bucket wheel steel structure by more than 14% leads to the appearance of unfavourable dynamic effects, even though the SS CoG position is preserved.",
publisher = "Elsevier Sci Ltd, Oxford",
journal = "Engineering Structures",
title = "Bucket wheel excavators: Dynamic response as a criterion for validation of the total number of buckets",
volume = "225",
doi = "10.1016/j.engstruct.2020.111313"
}

Gnjatović, N., Bošnjak, S., Milenović, I. Lj.,& Stefanović, A. Z.. (2020). Bucket wheel excavators: Dynamic response as a criterion for validation of the total number of buckets. in Engineering Structures
Elsevier Sci Ltd, Oxford., 225.
https://doi.org/10.1016/j.engstruct.2020.111313

Gnjatović N, Bošnjak S, Milenović IL, Stefanović AZ. Bucket wheel excavators: Dynamic response as a criterion for validation of the total number of buckets. in Engineering Structures. 2020;225.
doi:10.1016/j.engstruct.2020.111313 .

Gnjatović, Nebojša, Bošnjak, Srđan, Milenović, Ivan Lj., Stefanović, Aleksandar Z., "Bucket wheel excavators: Dynamic response as a criterion for validation of the total number of buckets" in Engineering Structures, 225 (2020),
https://doi.org/10.1016/j.engstruct.2020.111313 . .

TY  - JOUR
AU  - Milovanović, Aleksandar
AU  - Sedmak, Aleksandar
AU  - Gnjatović, Nebojša
PY  - 2020
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/3374
AB  - Fracture mechanics parameters have been applied to assess pressure vessel integrity. The pressure vessel analysed here was the ammonia spherical tank (volume of 1800 m(3), outer diameter 15.12 m, thickness 30 mm) where different cracks in the longitudinal and transverse butt joints were found. The finite element method was used to calculate stress and strain state and to analyse cracks and their influence on spherical storage tank integrity. Toward this end, the stress intensity factors were analytically determined, and compared with the fracture toughness to find out the critical pressure using Failure Assessment Diagram (FAD) in combination with net stress vs. critical stress.
PB  - Univ Osijek, Tech Fac, Slavonski Brod
T2  - Tehnički vjesnik
T1  - Application of Fracture Mechanics Parameters to Spherical Storage Tank Integrity Assessment
EP  - 1596
IS  - 5
SP  - 1592
VL  - 27
DO  - 10.17559/TV-20191021140800
ER  - 

@article{
author = "Milovanović, Aleksandar and Sedmak, Aleksandar and Gnjatović, Nebojša",
year = "2020",
abstract = "Fracture mechanics parameters have been applied to assess pressure vessel integrity. The pressure vessel analysed here was the ammonia spherical tank (volume of 1800 m(3), outer diameter 15.12 m, thickness 30 mm) where different cracks in the longitudinal and transverse butt joints were found. The finite element method was used to calculate stress and strain state and to analyse cracks and their influence on spherical storage tank integrity. Toward this end, the stress intensity factors were analytically determined, and compared with the fracture toughness to find out the critical pressure using Failure Assessment Diagram (FAD) in combination with net stress vs. critical stress.",
publisher = "Univ Osijek, Tech Fac, Slavonski Brod",
journal = "Tehnički vjesnik",
title = "Application of Fracture Mechanics Parameters to Spherical Storage Tank Integrity Assessment",
pages = "1596-1592",
number = "5",
volume = "27",
doi = "10.17559/TV-20191021140800"
}

Milovanović, A., Sedmak, A.,& Gnjatović, N.. (2020). Application of Fracture Mechanics Parameters to Spherical Storage Tank Integrity Assessment. in Tehnički vjesnik
Univ Osijek, Tech Fac, Slavonski Brod., 27(5), 1592-1596.
https://doi.org/10.17559/TV-20191021140800

Milovanović A, Sedmak A, Gnjatović N. Application of Fracture Mechanics Parameters to Spherical Storage Tank Integrity Assessment. in Tehnički vjesnik. 2020;27(5):1592-1596.
doi:10.17559/TV-20191021140800 .

Milovanović, Aleksandar, Sedmak, Aleksandar, Gnjatović, Nebojša, "Application of Fracture Mechanics Parameters to Spherical Storage Tank Integrity Assessment" in Tehnički vjesnik, 27, no. 5 (2020):1592-1596,
https://doi.org/10.17559/TV-20191021140800 . .

TY  - JOUR
AU  - Gnjatović, Nebojša
AU  - Bošnjak, Srđan
AU  - Milenović, Ivan Lj.
PY  - 2020
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/3302
AB  - Exploitation of bucket wheel excavators (BWEs) is accompanied by an increase of mass due to transport and adherence of a large amount of the material. Technical regulations do not account for the dynamic behaviour of BWEs. Such problems are analysed as quasi-static. A procedure and results of investigation of the influence of masses of the bucket wheel (BW) incrustation and soil in a blocked BW chute on the superstructure response are presented. Analysis of sensitivity of dynamic characteristics and the response to adherence of the material is conducted. The method and results can be used in the design stages of new and in reconstructions of obsolete BWEs.
PB  - Polish Soc Theoretical & Applied Mechanics, Warszawa
T2  - Journal of Theoretical and Applied Mechanics
T1  - The influence of incrustation and chute blockage on the dynamic behaviour of a bucket wheel excavator slewing superstructure
EP  - 584
IS  - 3
SP  - 573
VL  - 58
DO  - 10.15632/jtam-pl/121942
ER  - 

@article{
author = "Gnjatović, Nebojša and Bošnjak, Srđan and Milenović, Ivan Lj.",
year = "2020",
abstract = "Exploitation of bucket wheel excavators (BWEs) is accompanied by an increase of mass due to transport and adherence of a large amount of the material. Technical regulations do not account for the dynamic behaviour of BWEs. Such problems are analysed as quasi-static. A procedure and results of investigation of the influence of masses of the bucket wheel (BW) incrustation and soil in a blocked BW chute on the superstructure response are presented. Analysis of sensitivity of dynamic characteristics and the response to adherence of the material is conducted. The method and results can be used in the design stages of new and in reconstructions of obsolete BWEs.",
publisher = "Polish Soc Theoretical & Applied Mechanics, Warszawa",
journal = "Journal of Theoretical and Applied Mechanics",
title = "The influence of incrustation and chute blockage on the dynamic behaviour of a bucket wheel excavator slewing superstructure",
pages = "584-573",
number = "3",
volume = "58",
doi = "10.15632/jtam-pl/121942"
}

Gnjatović, N., Bošnjak, S.,& Milenović, I. Lj.. (2020). The influence of incrustation and chute blockage on the dynamic behaviour of a bucket wheel excavator slewing superstructure. in Journal of Theoretical and Applied Mechanics
Polish Soc Theoretical & Applied Mechanics, Warszawa., 58(3), 573-584.
https://doi.org/10.15632/jtam-pl/121942

Gnjatović N, Bošnjak S, Milenović IL. The influence of incrustation and chute blockage on the dynamic behaviour of a bucket wheel excavator slewing superstructure. in Journal of Theoretical and Applied Mechanics. 2020;58(3):573-584.
doi:10.15632/jtam-pl/121942 .

Gnjatović, Nebojša, Bošnjak, Srđan, Milenović, Ivan Lj., "The influence of incrustation and chute blockage on the dynamic behaviour of a bucket wheel excavator slewing superstructure" in Journal of Theoretical and Applied Mechanics, 58, no. 3 (2020):573-584,
https://doi.org/10.15632/jtam-pl/121942 . .

TY  - JOUR
AU  - Arsić, Dušan
AU  - Gnjatović, Nebojša
AU  - Sedmak, Simon
AU  - Arsić, Aleksandra
AU  - Uhricik, Milan
PY  - 2019
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/3056
AB  - In this paper are presented results of tests and analyses of complex dynamic loads carried out on the bucket-wheel excavator SchRs 650/5x24 Krupp, as well as assessment of service life of vital welded structures of a bucket-wheel excavator boom subjected to cyclic loading with a variable amplitude through the use of experimental tests carried out in order to determine operational strength and growth of a fatigue crack for one structural part. Bucket-wheel excavator was built by "Thyssen Krupp" company, Germany. Outer loads, or in other words digging forces for the overburden and coal have been calculated on the basis of measured values of actual current intensity of the bucket-wheel drive and recorded output values of changeable loads. Correlations between the power of the bucket-wheel drive system and adequate hourly production, depending on the overall digging resistance which affects the stress condition of the bucket-wheel, were also determined. Results of the theoretical and experimental analysis of natural and forced oscillations of the support structure for various exploitation conditions are presented in first part of the paper. Deformations epsilon(i) determined by tensometric measurements on the rotating shaft of the bucket-wheel were converted into tangential stresses through the introduction of the modulus of elasticity and Poisson's ratio, which, along with the polar moment of inertia of the cross-section, define the moment of rotation on the bucket-wheel shaft. Through the use of the load - strength comparison method (maximization of the ratio of load and strength indicators) the application factor of the gear with the largest number of turns K-A has been determined. In the second part of the paper methodological approach for the assessment of service life of vital welded structures of a bucket-wheel excavator boom was presented. Assessment was done in order to determine operational strength and growth of a fatigue crack, through the use of experimental tests. Realized researches and results presented in this paper offer great possibilities for the analyses of behaviour of vital welded structures of the bucket-wheel boom. By the application of the measurement device with 8 channels for registration and processing of electric signals HBM Spider 8 and measurement tapes HBM 6/350xXY31 deformations were measured at vital welded structures of the boom in the area of the bucket-wheel. The objective of the test is to determine if there is a possibility of occurrence of plastic deformations or initial cracks due to fatigue at vital welded structures and to obtain data which define crack growth.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Engineering Failure Analysis
T1  - Integrity assessment and determination of residual fatigue life of vital parts of bucket-wheel excavator operating under dynamic loads
EP  - 195
SP  - 182
VL  - 105
DO  - 10.1016/j.engfailanal.2019.06.072
ER  - 

@article{
author = "Arsić, Dušan and Gnjatović, Nebojša and Sedmak, Simon and Arsić, Aleksandra and Uhricik, Milan",
year = "2019",
abstract = "In this paper are presented results of tests and analyses of complex dynamic loads carried out on the bucket-wheel excavator SchRs 650/5x24 Krupp, as well as assessment of service life of vital welded structures of a bucket-wheel excavator boom subjected to cyclic loading with a variable amplitude through the use of experimental tests carried out in order to determine operational strength and growth of a fatigue crack for one structural part. Bucket-wheel excavator was built by "Thyssen Krupp" company, Germany. Outer loads, or in other words digging forces for the overburden and coal have been calculated on the basis of measured values of actual current intensity of the bucket-wheel drive and recorded output values of changeable loads. Correlations between the power of the bucket-wheel drive system and adequate hourly production, depending on the overall digging resistance which affects the stress condition of the bucket-wheel, were also determined. Results of the theoretical and experimental analysis of natural and forced oscillations of the support structure for various exploitation conditions are presented in first part of the paper. Deformations epsilon(i) determined by tensometric measurements on the rotating shaft of the bucket-wheel were converted into tangential stresses through the introduction of the modulus of elasticity and Poisson's ratio, which, along with the polar moment of inertia of the cross-section, define the moment of rotation on the bucket-wheel shaft. Through the use of the load - strength comparison method (maximization of the ratio of load and strength indicators) the application factor of the gear with the largest number of turns K-A has been determined. In the second part of the paper methodological approach for the assessment of service life of vital welded structures of a bucket-wheel excavator boom was presented. Assessment was done in order to determine operational strength and growth of a fatigue crack, through the use of experimental tests. Realized researches and results presented in this paper offer great possibilities for the analyses of behaviour of vital welded structures of the bucket-wheel boom. By the application of the measurement device with 8 channels for registration and processing of electric signals HBM Spider 8 and measurement tapes HBM 6/350xXY31 deformations were measured at vital welded structures of the boom in the area of the bucket-wheel. The objective of the test is to determine if there is a possibility of occurrence of plastic deformations or initial cracks due to fatigue at vital welded structures and to obtain data which define crack growth.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Engineering Failure Analysis",
title = "Integrity assessment and determination of residual fatigue life of vital parts of bucket-wheel excavator operating under dynamic loads",
pages = "195-182",
volume = "105",
doi = "10.1016/j.engfailanal.2019.06.072"
}

Arsić, D., Gnjatović, N., Sedmak, S., Arsić, A.,& Uhricik, M.. (2019). Integrity assessment and determination of residual fatigue life of vital parts of bucket-wheel excavator operating under dynamic loads. in Engineering Failure Analysis
Pergamon-Elsevier Science Ltd, Oxford., 105, 182-195.
https://doi.org/10.1016/j.engfailanal.2019.06.072

Arsić D, Gnjatović N, Sedmak S, Arsić A, Uhricik M. Integrity assessment and determination of residual fatigue life of vital parts of bucket-wheel excavator operating under dynamic loads. in Engineering Failure Analysis. 2019;105:182-195.
doi:10.1016/j.engfailanal.2019.06.072 .

Arsić, Dušan, Gnjatović, Nebojša, Sedmak, Simon, Arsić, Aleksandra, Uhricik, Milan, "Integrity assessment and determination of residual fatigue life of vital parts of bucket-wheel excavator operating under dynamic loads" in Engineering Failure Analysis, 105 (2019):182-195,
https://doi.org/10.1016/j.engfailanal.2019.06.072 . .

TY  - CONF
AU  - Arsić, Miodrag
AU  - Bošnjak, Srđan
AU  - Grabulov, Vencislav
AU  - Gnjatović, Nebojša
AU  - Milenović, Ivan Lj.
PY  - 2019
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/4938
AB  - Damaging of the carrying steel structure and embedding of the rejecting drum of the stacker conveyor occurred during the exploitation of the bucket-wheel reclaimer with the belonging stacker. The analysis of the cause and level of damaging led to the conclusion that damaged parts should be replaced by new ones and that methodology of repair should be based on the application of a suitable welding technology. This paper presents the methodology of repair welding performed during the replacement of the damaged carrying structure and embedding of the rejecting drum of the stacker conveyor which consist of steel sheets and profiles that’s based on the conceptual solution for damage repair through the use of program package ’Catia’ – V5 that enabled the creation of models and graphic documentation of structural parts that should be replaced by new ones. It should also be noted that geodetic survey of the lower belt of the stacker structure was performed after the substitution of damaged parts of the structure.
PB  - University of Belgrade, Faculty of Mechanical Engineering
C3  - Proceedings of the XXIII International Conference MHCL’19
T1  - Repair methodology for the carrying structure of the rejecting drum of the bucket-wheel reclaimer stacker conveyor at coal landfill
EP  - 122
SP  - 117
UR  - https://hdl.handle.net/21.15107/rcub_machinery_4938
ER  - 

@conference{
author = "Arsić, Miodrag and Bošnjak, Srđan and Grabulov, Vencislav and Gnjatović, Nebojša and Milenović, Ivan Lj.",
year = "2019",
abstract = "Damaging of the carrying steel structure and embedding of the rejecting drum of the stacker conveyor occurred during the exploitation of the bucket-wheel reclaimer with the belonging stacker. The analysis of the cause and level of damaging led to the conclusion that damaged parts should be replaced by new ones and that methodology of repair should be based on the application of a suitable welding technology. This paper presents the methodology of repair welding performed during the replacement of the damaged carrying structure and embedding of the rejecting drum of the stacker conveyor which consist of steel sheets and profiles that’s based on the conceptual solution for damage repair through the use of program package ’Catia’ – V5 that enabled the creation of models and graphic documentation of structural parts that should be replaced by new ones. It should also be noted that geodetic survey of the lower belt of the stacker structure was performed after the substitution of damaged parts of the structure.",
publisher = "University of Belgrade, Faculty of Mechanical Engineering",
journal = "Proceedings of the XXIII International Conference MHCL’19",
title = "Repair methodology for the carrying structure of the rejecting drum of the bucket-wheel reclaimer stacker conveyor at coal landfill",
pages = "122-117",
url = "https://hdl.handle.net/21.15107/rcub_machinery_4938"
}

Arsić, M., Bošnjak, S., Grabulov, V., Gnjatović, N.,& Milenović, I. Lj.. (2019). Repair methodology for the carrying structure of the rejecting drum of the bucket-wheel reclaimer stacker conveyor at coal landfill. in Proceedings of the XXIII International Conference MHCL’19
University of Belgrade, Faculty of Mechanical Engineering., 117-122.
https://hdl.handle.net/21.15107/rcub_machinery_4938

Arsić M, Bošnjak S, Grabulov V, Gnjatović N, Milenović IL. Repair methodology for the carrying structure of the rejecting drum of the bucket-wheel reclaimer stacker conveyor at coal landfill. in Proceedings of the XXIII International Conference MHCL’19. 2019;:117-122.
https://hdl.handle.net/21.15107/rcub_machinery_4938 .

Arsić, Miodrag, Bošnjak, Srđan, Grabulov, Vencislav, Gnjatović, Nebojša, Milenović, Ivan Lj., "Repair methodology for the carrying structure of the rejecting drum of the bucket-wheel reclaimer stacker conveyor at coal landfill" in Proceedings of the XXIII International Conference MHCL’19 (2019):117-122,
https://hdl.handle.net/21.15107/rcub_machinery_4938 .

TY  - CONF
AU  - Bošnjak, Srđan
AU  - Gnjatović, Nebojša
AU  - Milenović, Ivan Lj.
AU  - Stefanović, Aleksandar Z.
AU  - Urošević, Marko
PY  - 2019
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/4936
AB  - A bucket wheel with drive represents a vital subsystem of any bucket wheel excavator. A multidecadal experience in the exploitation and maintenance of bucket wheel excavators SRs 2000 has imposed a need for modernization and unification of the excavating devices of four of such machines, used for the excavation of overburden in Serbian open pit mines. This paper presents a portion of the research dedicated to the problems of strength and dynamic properties of the bucket wheel boom, static stability of the superstructure as well as installation of the unified design solution for the bucket wheel drive of the bucket wheel excavator SRs 2000. By
installing a modernized design solution of the bucket wheel with drive, i.e. by the means of partial revitalization of the bucket wheel excavator, its exploitational life span is prolonged and, additionally, the level of reliability and availability of the overburden systems is increased, and a
significant reduction in maintenance expenses is achieved.
PB  - University of Belgrade, Faculty of Mechanical Engineering
C3  - Proceedings of the XXIII International Conference MHCL’19
T1  - Modernization and unification of the excavating devices of bucket wheel excavators SRs 2000 deployed in Serbian open pit mines
EP  - 182
SP  - 175
UR  - https://hdl.handle.net/21.15107/rcub_machinery_4936
ER  - 

@conference{
author = "Bošnjak, Srđan and Gnjatović, Nebojša and Milenović, Ivan Lj. and Stefanović, Aleksandar Z. and Urošević, Marko",
year = "2019",
abstract = "A bucket wheel with drive represents a vital subsystem of any bucket wheel excavator. A multidecadal experience in the exploitation and maintenance of bucket wheel excavators SRs 2000 has imposed a need for modernization and unification of the excavating devices of four of such machines, used for the excavation of overburden in Serbian open pit mines. This paper presents a portion of the research dedicated to the problems of strength and dynamic properties of the bucket wheel boom, static stability of the superstructure as well as installation of the unified design solution for the bucket wheel drive of the bucket wheel excavator SRs 2000. By
installing a modernized design solution of the bucket wheel with drive, i.e. by the means of partial revitalization of the bucket wheel excavator, its exploitational life span is prolonged and, additionally, the level of reliability and availability of the overburden systems is increased, and a
significant reduction in maintenance expenses is achieved.",
publisher = "University of Belgrade, Faculty of Mechanical Engineering",
journal = "Proceedings of the XXIII International Conference MHCL’19",
title = "Modernization and unification of the excavating devices of bucket wheel excavators SRs 2000 deployed in Serbian open pit mines",
pages = "182-175",
url = "https://hdl.handle.net/21.15107/rcub_machinery_4936"
}

Bošnjak, S., Gnjatović, N., Milenović, I. Lj., Stefanović, A. Z.,& Urošević, M.. (2019). Modernization and unification of the excavating devices of bucket wheel excavators SRs 2000 deployed in Serbian open pit mines. in Proceedings of the XXIII International Conference MHCL’19
University of Belgrade, Faculty of Mechanical Engineering., 175-182.
https://hdl.handle.net/21.15107/rcub_machinery_4936

Bošnjak S, Gnjatović N, Milenović IL, Stefanović AZ, Urošević M. Modernization and unification of the excavating devices of bucket wheel excavators SRs 2000 deployed in Serbian open pit mines. in Proceedings of the XXIII International Conference MHCL’19. 2019;:175-182.
https://hdl.handle.net/21.15107/rcub_machinery_4936 .

Bošnjak, Srđan, Gnjatović, Nebojša, Milenović, Ivan Lj., Stefanović, Aleksandar Z., Urošević, Marko, "Modernization and unification of the excavating devices of bucket wheel excavators SRs 2000 deployed in Serbian open pit mines" in Proceedings of the XXIII International Conference MHCL’19 (2019):175-182,
https://hdl.handle.net/21.15107/rcub_machinery_4936 .

TY  - CONF
AU  - Gnjatović, Nebojša
AU  - Bošnjak, Srđan
AU  - Milenović, Ivan Lj.
AU  - Stefanović, Aleksandar Z.
PY  - 2019
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/4934
AB  - The method for validation of the number of buckets on the working device of a bucket wheel excavator from the aspect of dynamic behaviour of the system, partially presented in this paper, was developed on the basis of the original spatial reduced dynamic model of the bucket wheel excavator with two masts, which enables modal analysis and analysis of the dynamic
response of the system for continuous variation of constructional parameters and parameters of excitation. The set of 16 seemingly acceptable solutions, all of which satisfied the rigid design restrictions which were: (a) use of the same bucket wheel drivetrain, (b) preservation of the theoretical capacity, (c) possibility of the excavation of soil of the fourth category and (d) preservation of the superstructure centre of gravity position, was analyzed. On the basis of limiting vertical and lateral accelerations, derived from dynamic coefficients prescribed by the code DIN 22261-2, of the bucket wheel centre, which for a proper geometrically-designed bucket wheel excavator structure represents a well grounded indicator of its dynamic behaviour, 14 out of 16 analyzed solutions were discarded, yielding the set of possible solutions to only 2, the originally designed one (with 17 buckets) and the solution with 20 buckets installed on the bucket wheel.
PB  - University of Belgrade, Faculty of Mechanical Engineering
C3  - Proceedings of the XXIII International Conference MHCL’19
T1  - Validation of the number of buckets on the working device of a bucket wheel
EP  - 196
SP  - 187
UR  - https://hdl.handle.net/21.15107/rcub_machinery_4934
ER  - 

@conference{
author = "Gnjatović, Nebojša and Bošnjak, Srđan and Milenović, Ivan Lj. and Stefanović, Aleksandar Z.",
year = "2019",
abstract = "The method for validation of the number of buckets on the working device of a bucket wheel excavator from the aspect of dynamic behaviour of the system, partially presented in this paper, was developed on the basis of the original spatial reduced dynamic model of the bucket wheel excavator with two masts, which enables modal analysis and analysis of the dynamic
response of the system for continuous variation of constructional parameters and parameters of excitation. The set of 16 seemingly acceptable solutions, all of which satisfied the rigid design restrictions which were: (a) use of the same bucket wheel drivetrain, (b) preservation of the theoretical capacity, (c) possibility of the excavation of soil of the fourth category and (d) preservation of the superstructure centre of gravity position, was analyzed. On the basis of limiting vertical and lateral accelerations, derived from dynamic coefficients prescribed by the code DIN 22261-2, of the bucket wheel centre, which for a proper geometrically-designed bucket wheel excavator structure represents a well grounded indicator of its dynamic behaviour, 14 out of 16 analyzed solutions were discarded, yielding the set of possible solutions to only 2, the originally designed one (with 17 buckets) and the solution with 20 buckets installed on the bucket wheel.",
publisher = "University of Belgrade, Faculty of Mechanical Engineering",
journal = "Proceedings of the XXIII International Conference MHCL’19",
title = "Validation of the number of buckets on the working device of a bucket wheel",
pages = "196-187",
url = "https://hdl.handle.net/21.15107/rcub_machinery_4934"
}

Gnjatović, N., Bošnjak, S., Milenović, I. Lj.,& Stefanović, A. Z.. (2019). Validation of the number of buckets on the working device of a bucket wheel. in Proceedings of the XXIII International Conference MHCL’19
University of Belgrade, Faculty of Mechanical Engineering., 187-196.
https://hdl.handle.net/21.15107/rcub_machinery_4934

Gnjatović N, Bošnjak S, Milenović IL, Stefanović AZ. Validation of the number of buckets on the working device of a bucket wheel. in Proceedings of the XXIII International Conference MHCL’19. 2019;:187-196.
https://hdl.handle.net/21.15107/rcub_machinery_4934 .

Gnjatović, Nebojša, Bošnjak, Srđan, Milenović, Ivan Lj., Stefanović, Aleksandar Z., "Validation of the number of buckets on the working device of a bucket wheel" in Proceedings of the XXIII International Conference MHCL’19 (2019):187-196,
https://hdl.handle.net/21.15107/rcub_machinery_4934 .

TY  - CHAP
AU  - Gnjatović, Nebojša
AU  - Bošnjak, Srđan
AU  - Zrnić, Nenad
PY  - 2019
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/3238
AB  - A holistic approach to analyzing the dynamic behaviour of a bucket wheel excavator (BWE) superstructure, which is practically neglected by technical regulations but nowadays widely used during their design and redesign, is presented in the paper. The procedure for determining the potential and kinetic energy and the vector of generalized non-potential forces of the system, leading to the development of a reduced spatial dynamic (RD) model of the BWE with two masts is presented in detail. Direct validation of the established model has been performed by comparing the values obtained for the first ten natural frequencies (NFs) of the finite element (FE) model to those obtained by the RD model. Percent deviations of values of the NFs obtained for the RD model are very low compared to those obtained by the FE model (~1% for three fundamental NFs). Indirect validation of the RD model used in this research i.e. validation of values of the NFs which have been obtained by calculation and the respective modal deflection shapes has been achieved by comparing them to the studies containing the results of numerical-experimental research on the dynamic characteristics of BWEs of the same design concept. The values of NFs are of the same order of magnitude and the corresponding deflection shapes are in full compliance with those of the experimentally-analyzed BWEs.
PB  - Pleiades journals
T2  - Lecture Notes in Mechanical Engineering
T1  - Spatial reduced dynamic model of a bucket wheel excavator with two masts
EP  - 235
SP  - 215
DO  - 10.1007/978-3-030-04975-1_26
ER  - 

@inbook{
author = "Gnjatović, Nebojša and Bošnjak, Srđan and Zrnić, Nenad",
year = "2019",
abstract = "A holistic approach to analyzing the dynamic behaviour of a bucket wheel excavator (BWE) superstructure, which is practically neglected by technical regulations but nowadays widely used during their design and redesign, is presented in the paper. The procedure for determining the potential and kinetic energy and the vector of generalized non-potential forces of the system, leading to the development of a reduced spatial dynamic (RD) model of the BWE with two masts is presented in detail. Direct validation of the established model has been performed by comparing the values obtained for the first ten natural frequencies (NFs) of the finite element (FE) model to those obtained by the RD model. Percent deviations of values of the NFs obtained for the RD model are very low compared to those obtained by the FE model (~1% for three fundamental NFs). Indirect validation of the RD model used in this research i.e. validation of values of the NFs which have been obtained by calculation and the respective modal deflection shapes has been achieved by comparing them to the studies containing the results of numerical-experimental research on the dynamic characteristics of BWEs of the same design concept. The values of NFs are of the same order of magnitude and the corresponding deflection shapes are in full compliance with those of the experimentally-analyzed BWEs.",
publisher = "Pleiades journals",
journal = "Lecture Notes in Mechanical Engineering",
booktitle = "Spatial reduced dynamic model of a bucket wheel excavator with two masts",
pages = "235-215",
doi = "10.1007/978-3-030-04975-1_26"
}

Gnjatović, N., Bošnjak, S.,& Zrnić, N.. (2019). Spatial reduced dynamic model of a bucket wheel excavator with two masts. in Lecture Notes in Mechanical Engineering
Pleiades journals., 215-235.
https://doi.org/10.1007/978-3-030-04975-1_26

Gnjatović N, Bošnjak S, Zrnić N. Spatial reduced dynamic model of a bucket wheel excavator with two masts. in Lecture Notes in Mechanical Engineering. 2019;:215-235.
doi:10.1007/978-3-030-04975-1_26 .

Gnjatović, Nebojša, Bošnjak, Srđan, Zrnić, Nenad, "Spatial reduced dynamic model of a bucket wheel excavator with two masts" in Lecture Notes in Mechanical Engineering (2019):215-235,
https://doi.org/10.1007/978-3-030-04975-1_26 . .

TY  - CONF
AU  - Arsić, Miodrag
AU  - Bošnjak, Srđan
AU  - Gnjatović, Nebojša
AU  - Sedmak, Simon
AU  - Arsić, D.
AU  - Savić, Zoran
PY  - 2018
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2918
AB  - This paper presents a methodological approach for the assessment of service life of vital welded structures of a bucket-wheel excavator Sch Rs 650/5x24 ('Thyssen Krupp', Germany) boom, subjected to cyclic loading with a variable amplitude through the use of experimental tests carried out in order to determine operational strength and growth of a fatigue crack. Realized researches and results presented in this paper offer great possibilities for the analyses of behaviour of vital welded structures of the bucket-wheel boom. By the application of the measurement device with 8 channels for registration and processing of electric signals HBM Spider 8 and measurement tapes HBM 6/350xXY31 deformations were measured at vital welded structures of the boom in the area of the bucket-wheel, made of steels St 37.2 and St 52.3 in accordance with standard DIN 17100, or steels S235J2G3 and S355J2G3 in accordance with standard EN 10025-2. The objective of the test is to determine if there is a possibility of occurrence of plastic deformations or initial cracks due to fatigue at vital welded structures. Tests that refer to the growth of the fatigue crack located at the welded joint have been carried out by bending at three points with asymmetric load R = 0.5 (R = sigma(min) / sigma(max)) at the specimen with a single edge notch. Tests were performed through the use of controlled force, ranging between F-max and F-min at the high frequency pulsator 'Cracktronic', while obtainment of data regarding the crack growth was carried out through the use of measurement gauge ARM A-10.
PB  - Elsevier Science Bv, Amsterdam
C3  - Procedia Structural Integrity - ECF22 - Loading and environmental effects on structural integrity
T1  - Determination of Residual Fatigue Life of Welded Structures at Bucket-Wheel Excavators through the Use of Fracture Mechanics
EP  - 84
SP  - 79
VL  - 13
DO  - 10.1016/j.prostr.2018.12.014
ER  - 

@conference{
author = "Arsić, Miodrag and Bošnjak, Srđan and Gnjatović, Nebojša and Sedmak, Simon and Arsić, D. and Savić, Zoran",
year = "2018",
abstract = "This paper presents a methodological approach for the assessment of service life of vital welded structures of a bucket-wheel excavator Sch Rs 650/5x24 ('Thyssen Krupp', Germany) boom, subjected to cyclic loading with a variable amplitude through the use of experimental tests carried out in order to determine operational strength and growth of a fatigue crack. Realized researches and results presented in this paper offer great possibilities for the analyses of behaviour of vital welded structures of the bucket-wheel boom. By the application of the measurement device with 8 channels for registration and processing of electric signals HBM Spider 8 and measurement tapes HBM 6/350xXY31 deformations were measured at vital welded structures of the boom in the area of the bucket-wheel, made of steels St 37.2 and St 52.3 in accordance with standard DIN 17100, or steels S235J2G3 and S355J2G3 in accordance with standard EN 10025-2. The objective of the test is to determine if there is a possibility of occurrence of plastic deformations or initial cracks due to fatigue at vital welded structures. Tests that refer to the growth of the fatigue crack located at the welded joint have been carried out by bending at three points with asymmetric load R = 0.5 (R = sigma(min) / sigma(max)) at the specimen with a single edge notch. Tests were performed through the use of controlled force, ranging between F-max and F-min at the high frequency pulsator 'Cracktronic', while obtainment of data regarding the crack growth was carried out through the use of measurement gauge ARM A-10.",
publisher = "Elsevier Science Bv, Amsterdam",
journal = "Procedia Structural Integrity - ECF22 - Loading and environmental effects on structural integrity",
title = "Determination of Residual Fatigue Life of Welded Structures at Bucket-Wheel Excavators through the Use of Fracture Mechanics",
pages = "84-79",
volume = "13",
doi = "10.1016/j.prostr.2018.12.014"
}

Arsić, M., Bošnjak, S., Gnjatović, N., Sedmak, S., Arsić, D.,& Savić, Z.. (2018). Determination of Residual Fatigue Life of Welded Structures at Bucket-Wheel Excavators through the Use of Fracture Mechanics. in Procedia Structural Integrity - ECF22 - Loading and environmental effects on structural integrity
Elsevier Science Bv, Amsterdam., 13, 79-84.
https://doi.org/10.1016/j.prostr.2018.12.014

Arsić M, Bošnjak S, Gnjatović N, Sedmak S, Arsić D, Savić Z. Determination of Residual Fatigue Life of Welded Structures at Bucket-Wheel Excavators through the Use of Fracture Mechanics. in Procedia Structural Integrity - ECF22 - Loading and environmental effects on structural integrity. 2018;13:79-84.
doi:10.1016/j.prostr.2018.12.014 .

Arsić, Miodrag, Bošnjak, Srđan, Gnjatović, Nebojša, Sedmak, Simon, Arsić, D., Savić, Zoran, "Determination of Residual Fatigue Life of Welded Structures at Bucket-Wheel Excavators through the Use of Fracture Mechanics" in Procedia Structural Integrity - ECF22 - Loading and environmental effects on structural integrity, 13 (2018):79-84,
https://doi.org/10.1016/j.prostr.2018.12.014 . .

TY  - CONF
AU  - Jovančić, Predrag
AU  - Ignjatović, Dragan
AU  - Gnjatović, Nebojša
AU  - Bošnjak, Srđan
PY  - 2018
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/5047
AB  - Na površinskim kopovima EPS trenutno je u funkciji 4 rotorna bagera tipa SRs 2000. Bageri
su nabavljani i montirani u različitim periodima što je uslovilo da ovi bageri imaju različita
konstruktivna rešenja najvitalnijeg dela - glave rotora. Tokom dosadašnje eksploatacije ovih
bagera na našim površinskim kopovima, kao najslabija mesta pokazali su se sistemi za pogon
rotornog točka i sam rotor. To iziskuje optimalno definisanje modernizacije i revitalizacije
odnosno unifikacije pogonske grupe rotora, što bi trebalo da obezbedi povećanje pouzdanosti
bagera, a time i povećanje vremenskog i kapacitetnog iskorišćenja. Na osnovu sistematizovanja
zapažanja i primedbi korisnika i održavalaca ovih rotornih bagera kao i hronologije problema
u radu, vrši se analiza pogona kopanja na svim bagerima i donosi krajnji stav o mogućim daljim
aktivnostima sa ciljem unifikacije.
PB  - Jugoslovenski komitet za površinsku eksploataciju
C3  - Зборник радова XIII међународне конференције „OMC 2018“
T1  - Анализа погонских система на багерима SRs 2000 са циљем унификације
EP  - 71
SP  - 63
UR  - https://hdl.handle.net/21.15107/rcub_machinery_5047
ER  - 

@conference{
author = "Jovančić, Predrag and Ignjatović, Dragan and Gnjatović, Nebojša and Bošnjak, Srđan",
year = "2018",
abstract = "Na površinskim kopovima EPS trenutno je u funkciji 4 rotorna bagera tipa SRs 2000. Bageri
su nabavljani i montirani u različitim periodima što je uslovilo da ovi bageri imaju različita
konstruktivna rešenja najvitalnijeg dela - glave rotora. Tokom dosadašnje eksploatacije ovih
bagera na našim površinskim kopovima, kao najslabija mesta pokazali su se sistemi za pogon
rotornog točka i sam rotor. To iziskuje optimalno definisanje modernizacije i revitalizacije
odnosno unifikacije pogonske grupe rotora, što bi trebalo da obezbedi povećanje pouzdanosti
bagera, a time i povećanje vremenskog i kapacitetnog iskorišćenja. Na osnovu sistematizovanja
zapažanja i primedbi korisnika i održavalaca ovih rotornih bagera kao i hronologije problema
u radu, vrši se analiza pogona kopanja na svim bagerima i donosi krajnji stav o mogućim daljim
aktivnostima sa ciljem unifikacije.",
publisher = "Jugoslovenski komitet za površinsku eksploataciju",
journal = "Зборник радова XIII међународне конференције „OMC 2018“",
title = "Анализа погонских система на багерима SRs 2000 са циљем унификације",
pages = "71-63",
url = "https://hdl.handle.net/21.15107/rcub_machinery_5047"
}

Jovančić, P., Ignjatović, D., Gnjatović, N.,& Bošnjak, S.. (2018). Анализа погонских система на багерима SRs 2000 са циљем унификације. in Зборник радова XIII међународне конференције „OMC 2018“
Jugoslovenski komitet za površinsku eksploataciju., 63-71.
https://hdl.handle.net/21.15107/rcub_machinery_5047

Jovančić P, Ignjatović D, Gnjatović N, Bošnjak S. Анализа погонских система на багерима SRs 2000 са циљем унификације. in Зборник радова XIII међународне конференције „OMC 2018“. 2018;:63-71.
https://hdl.handle.net/21.15107/rcub_machinery_5047 .

Jovančić, Predrag, Ignjatović, Dragan, Gnjatović, Nebojša, Bošnjak, Srđan, "Анализа погонских система на багерима SRs 2000 са циљем унификације" in Зборник радова XIII међународне конференције „OMC 2018“ (2018):63-71,
https://hdl.handle.net/21.15107/rcub_machinery_5047 .

TY  - JOUR
AU  - Mladenović, M.
AU  - Arsić, Miodrag
AU  - Savić, Zoran
AU  - Bošnjak, Srđan
AU  - Gnjatović, Nebojša
PY  - 2018
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/5011
AB  - Hydro power plant ’Perućica’, which comprises 7 hydroelectric generating units, each with installed power of 330 MW, is the oldest hydro power plant in Montenegro and was put in service in 1960. This high pressure hydro power plant is a complex hydroenergetic system, which consists of a 3335 m long concrete tunnel, surge with a broadening and overflow and three steel pipelines with two-sided Pelton turbines with horizontal shafts installed.Five turbines have nominal power of 38 MW, while two have nominal power of 58,5 MW (307 MW overall).
The biggest problem at hydro power plant ’Perućica’ refers to the parent material and weld metal of the breeches pipe 1A located at pipeline III. Significantly lesser problems were detected at parent material and weld metal of breeches pipes 7B, 8A and 8B. Pipeline and breeches pipes were made of microalloyed steel ’Nioval 47’ (steel mill ’Jesenice’). Stresses that occur at pipelines in service during the process of execution of functional tasks (stationary and dynamic loads) and during the disturbed process of exploitation (non-stationary dynamic loads) cause severe damaging of parent material and weld metal at structural components of breeches pipes (collars and anchors), thus endangering the integrity of pipeline structure as a whole. Role of the collar, which enables the leaning of the breeches pipe on the foundation, is to receive static and dynamic loads (mean pressure of up to 61 bar in pipeline axis, specific load that occurs due to the quantity of water in the pipeline, action of the force of gravity) and displacements which happen due to non-stationary dynamic loads that occur at the pipeline, while the anchor strengthens and balances the mass of the breeches pipe.
In this paper the results of non-destructive tests carried out on parent material and weld metal (collar and anchor) of breeches pipes with designations 1A, 7A, 8A and 8B and results of destructive tests performed on parent material of the anchor are presented. Tests that were carried out include visual testing (VT), magnetic particle testing (MT) and ultrasonic testing (UT), while destructive tests included determination of chemical composition, tensile properties, impact energy and hardness. On the basis of results of test results it was determined that the main cause of occurrence of significant damages (degradation of parent material of the anchor and weld metal between the collar and anchor, as well as between the pipeline and the anchor) at the structure of the breeches pipe 1A of the pipeline III at the hydro power plant ’Perućica’ is the fact that the breeches pipe did not lean on the collar, as was predicted by design, but on the anchor which, due to the size of its cross-section, could not endure all loads that occur at the breeches pipe during service. Damages that occurred on parent material and weld metal of breeches pipes 7B, 8A and 8B are directly caused by flaws in welding technology and conditions of exploitation. Executed researches showed that degradation of parent material and weld metal does not influence the integrity of the pipeline III as a whole.
T2  - Енергија, економија, екологија
T1  - Influence of degradation of parent-material and welded joints on the integrity of the breeches pipe located at pipeline iii of hydro power plant ‘Perućica’
EP  - 534
SP  - 528
VL  - 1-2
UR  - https://hdl.handle.net/21.15107/rcub_machinery_5011
ER  - 

@article{
author = "Mladenović, M. and Arsić, Miodrag and Savić, Zoran and Bošnjak, Srđan and Gnjatović, Nebojša",
year = "2018",
abstract = "Hydro power plant ’Perućica’, which comprises 7 hydroelectric generating units, each with installed power of 330 MW, is the oldest hydro power plant in Montenegro and was put in service in 1960. This high pressure hydro power plant is a complex hydroenergetic system, which consists of a 3335 m long concrete tunnel, surge with a broadening and overflow and three steel pipelines with two-sided Pelton turbines with horizontal shafts installed.Five turbines have nominal power of 38 MW, while two have nominal power of 58,5 MW (307 MW overall).
The biggest problem at hydro power plant ’Perućica’ refers to the parent material and weld metal of the breeches pipe 1A located at pipeline III. Significantly lesser problems were detected at parent material and weld metal of breeches pipes 7B, 8A and 8B. Pipeline and breeches pipes were made of microalloyed steel ’Nioval 47’ (steel mill ’Jesenice’). Stresses that occur at pipelines in service during the process of execution of functional tasks (stationary and dynamic loads) and during the disturbed process of exploitation (non-stationary dynamic loads) cause severe damaging of parent material and weld metal at structural components of breeches pipes (collars and anchors), thus endangering the integrity of pipeline structure as a whole. Role of the collar, which enables the leaning of the breeches pipe on the foundation, is to receive static and dynamic loads (mean pressure of up to 61 bar in pipeline axis, specific load that occurs due to the quantity of water in the pipeline, action of the force of gravity) and displacements which happen due to non-stationary dynamic loads that occur at the pipeline, while the anchor strengthens and balances the mass of the breeches pipe.
In this paper the results of non-destructive tests carried out on parent material and weld metal (collar and anchor) of breeches pipes with designations 1A, 7A, 8A and 8B and results of destructive tests performed on parent material of the anchor are presented. Tests that were carried out include visual testing (VT), magnetic particle testing (MT) and ultrasonic testing (UT), while destructive tests included determination of chemical composition, tensile properties, impact energy and hardness. On the basis of results of test results it was determined that the main cause of occurrence of significant damages (degradation of parent material of the anchor and weld metal between the collar and anchor, as well as between the pipeline and the anchor) at the structure of the breeches pipe 1A of the pipeline III at the hydro power plant ’Perućica’ is the fact that the breeches pipe did not lean on the collar, as was predicted by design, but on the anchor which, due to the size of its cross-section, could not endure all loads that occur at the breeches pipe during service. Damages that occurred on parent material and weld metal of breeches pipes 7B, 8A and 8B are directly caused by flaws in welding technology and conditions of exploitation. Executed researches showed that degradation of parent material and weld metal does not influence the integrity of the pipeline III as a whole.",
journal = "Енергија, економија, екологија",
title = "Influence of degradation of parent-material and welded joints on the integrity of the breeches pipe located at pipeline iii of hydro power plant ‘Perućica’",
pages = "534-528",
volume = "1-2",
url = "https://hdl.handle.net/21.15107/rcub_machinery_5011"
}

Mladenović, M., Arsić, M., Savić, Z., Bošnjak, S.,& Gnjatović, N.. (2018). Influence of degradation of parent-material and welded joints on the integrity of the breeches pipe located at pipeline iii of hydro power plant ‘Perućica’. in Енергија, економија, екологија, 1-2, 528-534.
https://hdl.handle.net/21.15107/rcub_machinery_5011

Mladenović M, Arsić M, Savić Z, Bošnjak S, Gnjatović N. Influence of degradation of parent-material and welded joints on the integrity of the breeches pipe located at pipeline iii of hydro power plant ‘Perućica’. in Енергија, економија, екологија. 2018;1-2:528-534.
https://hdl.handle.net/21.15107/rcub_machinery_5011 .

Mladenović, M., Arsić, Miodrag, Savić, Zoran, Bošnjak, Srđan, Gnjatović, Nebojša, "Influence of degradation of parent-material and welded joints on the integrity of the breeches pipe located at pipeline iii of hydro power plant ‘Perućica’" in Енергија, економија, екологија, 1-2 (2018):528-534,
https://hdl.handle.net/21.15107/rcub_machinery_5011 .

TY  - JOUR
AU  - Bošnjak, Srđan
AU  - Gnjatović, Nebojša
AU  - Milenović, Ivan Lj.
PY  - 2018
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2922
AB  - The complexity of the slewing superstructure (SS) balancing problem derives from the changeability of its geometric configuration, the complexity of working conditions as well as multiple limitations of the possible set of solutions. Having in mind the fact that the existing reference literature does not fully specify the procedure of static stability proof, the aforementioned procedure is presented in detail for the first time in this paper. A major contribution is represented in the classification of the slewing superstructure models into two groups which were named: the 'a priori' model (designed image of the SS) and the 'a posteriori' model (actual image of the SS). The fundamental stages of the 'a posteriori' model development method are presented in the paper. The transformation and validation of the calculation model 'a priori' to the calculation model 'a posteriori' was conducted on the basis of weighing results. A calculation of the basic parameters of the bucket wheel excavator (BWE) superstructure was conducted for both analyzed models by using the in-house developed software. The 'a posteriori' models provide a reliable calculation of the SS static stability and may be used not only for static stability proof of the machine as a whole, but also for load analysis of substructures and elements of BWE and related surface mining machines, such as spreaders. Besides that, the previously mentioned models are of extreme importance for a successful and reliable exploitation and maintenence of the machine since they present the basis for adjustment and control of limiting winch rope forces values, periodic control of mass and center of gravity position, as well as for a possible reconstruction which would be conducted in order to realize better customization of the machine versus operating conditions.
PB  - Polish Maintenance Soc, Lublin
T2  - Eksploatacja I Niezawodnosc-Maintenance and Reliability
T1  - From 'a priori' to 'a posteriori' static stability of the slewing superstructure of a bucket wheel excavator
EP  - 206
IS  - 2
SP  - 190
VL  - 20
DO  - 10.17531/ein.2018.2.04
ER  - 

@article{
author = "Bošnjak, Srđan and Gnjatović, Nebojša and Milenović, Ivan Lj.",
year = "2018",
abstract = "The complexity of the slewing superstructure (SS) balancing problem derives from the changeability of its geometric configuration, the complexity of working conditions as well as multiple limitations of the possible set of solutions. Having in mind the fact that the existing reference literature does not fully specify the procedure of static stability proof, the aforementioned procedure is presented in detail for the first time in this paper. A major contribution is represented in the classification of the slewing superstructure models into two groups which were named: the 'a priori' model (designed image of the SS) and the 'a posteriori' model (actual image of the SS). The fundamental stages of the 'a posteriori' model development method are presented in the paper. The transformation and validation of the calculation model 'a priori' to the calculation model 'a posteriori' was conducted on the basis of weighing results. A calculation of the basic parameters of the bucket wheel excavator (BWE) superstructure was conducted for both analyzed models by using the in-house developed software. The 'a posteriori' models provide a reliable calculation of the SS static stability and may be used not only for static stability proof of the machine as a whole, but also for load analysis of substructures and elements of BWE and related surface mining machines, such as spreaders. Besides that, the previously mentioned models are of extreme importance for a successful and reliable exploitation and maintenence of the machine since they present the basis for adjustment and control of limiting winch rope forces values, periodic control of mass and center of gravity position, as well as for a possible reconstruction which would be conducted in order to realize better customization of the machine versus operating conditions.",
publisher = "Polish Maintenance Soc, Lublin",
journal = "Eksploatacja I Niezawodnosc-Maintenance and Reliability",
title = "From 'a priori' to 'a posteriori' static stability of the slewing superstructure of a bucket wheel excavator",
pages = "206-190",
number = "2",
volume = "20",
doi = "10.17531/ein.2018.2.04"
}

Bošnjak, S., Gnjatović, N.,& Milenović, I. Lj.. (2018). From 'a priori' to 'a posteriori' static stability of the slewing superstructure of a bucket wheel excavator. in Eksploatacja I Niezawodnosc-Maintenance and Reliability
Polish Maintenance Soc, Lublin., 20(2), 190-206.
https://doi.org/10.17531/ein.2018.2.04

Bošnjak S, Gnjatović N, Milenović IL. From 'a priori' to 'a posteriori' static stability of the slewing superstructure of a bucket wheel excavator. in Eksploatacja I Niezawodnosc-Maintenance and Reliability. 2018;20(2):190-206.
doi:10.17531/ein.2018.2.04 .

Bošnjak, Srđan, Gnjatović, Nebojša, Milenović, Ivan Lj., "From 'a priori' to 'a posteriori' static stability of the slewing superstructure of a bucket wheel excavator" in Eksploatacja I Niezawodnosc-Maintenance and Reliability, 20, no. 2 (2018):190-206,
https://doi.org/10.17531/ein.2018.2.04 . .

TY  - JOUR
AU  - Gnjatović, Nebojša
AU  - Bošnjak, Srđan
AU  - Stefanović, Aleksandar Z.
PY  - 2018
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2819
AB  - Sensitivity analysis of the dynamic response of both the designed and the actual models of a slewing superstructure with two masts to the variation of the counterweight mass and the degree of accuracy of the approximation polynomials of the digging resistance was conducted in the paper. Spatial reduced dynamic models of the bucket wheel excavator SchRs 1600 were used as a basis for the presented investigations. Based on the comparative analysis of the calculation results, the following conclusions were drawn: (a) mass of the counterweight has a significantly higher influence on the maximum intensities of accelerations of the referent points than on the spectrum of natural frequencies, (b) the accuracy of approximations of the digging resistance and the maximum values of accelerations differ by an order of magnitude, for the approximation trigonometric polynomial of the same number of harmonics.
PB  - Polska Akad Nauk, Polish Acad Sciences, Warszawa
T2  - Archives of Mining Sciences
T1  - The dependency of the dynamic response of a two mast bucket wheel excavator superstructure on the counterweight mass and the degree of fourier approximation of the digging resistance
EP  - 509
IS  - 2
SP  - 491
VL  - 63
DO  - 10.24425/122909
ER  - 

@article{
author = "Gnjatović, Nebojša and Bošnjak, Srđan and Stefanović, Aleksandar Z.",
year = "2018",
abstract = "Sensitivity analysis of the dynamic response of both the designed and the actual models of a slewing superstructure with two masts to the variation of the counterweight mass and the degree of accuracy of the approximation polynomials of the digging resistance was conducted in the paper. Spatial reduced dynamic models of the bucket wheel excavator SchRs 1600 were used as a basis for the presented investigations. Based on the comparative analysis of the calculation results, the following conclusions were drawn: (a) mass of the counterweight has a significantly higher influence on the maximum intensities of accelerations of the referent points than on the spectrum of natural frequencies, (b) the accuracy of approximations of the digging resistance and the maximum values of accelerations differ by an order of magnitude, for the approximation trigonometric polynomial of the same number of harmonics.",
publisher = "Polska Akad Nauk, Polish Acad Sciences, Warszawa",
journal = "Archives of Mining Sciences",
title = "The dependency of the dynamic response of a two mast bucket wheel excavator superstructure on the counterweight mass and the degree of fourier approximation of the digging resistance",
pages = "509-491",
number = "2",
volume = "63",
doi = "10.24425/122909"
}

Gnjatović, N., Bošnjak, S.,& Stefanović, A. Z.. (2018). The dependency of the dynamic response of a two mast bucket wheel excavator superstructure on the counterweight mass and the degree of fourier approximation of the digging resistance. in Archives of Mining Sciences
Polska Akad Nauk, Polish Acad Sciences, Warszawa., 63(2), 491-509.
https://doi.org/10.24425/122909

Gnjatović N, Bošnjak S, Stefanović AZ. The dependency of the dynamic response of a two mast bucket wheel excavator superstructure on the counterweight mass and the degree of fourier approximation of the digging resistance. in Archives of Mining Sciences. 2018;63(2):491-509.
doi:10.24425/122909 .

Gnjatović, Nebojša, Bošnjak, Srđan, Stefanović, Aleksandar Z., "The dependency of the dynamic response of a two mast bucket wheel excavator superstructure on the counterweight mass and the degree of fourier approximation of the digging resistance" in Archives of Mining Sciences, 63, no. 2 (2018):491-509,
https://doi.org/10.24425/122909 . .