TY  - JOUR
AU  - Petrović, Veljko M.
AU  - Buljak, Vladimir
AU  - Cornaggia, Aram
PY  - 2021
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/3563
AB  - U ovom radu proučavan je uticaj neuniformnosti temperaturnog polja po uzorku na rezultate simulacije procesa sinterovanja. Kao konstitutivni model ponašanja materijala upotrebljen je modifikovan fenomenološki Skorohod-Olevski viskozni model sinterovanja. Poređeni su rezultati simulacije dobijeni korišćenjem uniformne raspodele temperature, sa rezultatima koji koriste temperaturno polje dobijeno simulacijom zagrevanj auzorka. Poređenja se odnose na uzorke različiti hveličina, kako bi se ispitao različiti nivo neuniformnosti. Dobijeni rezultati u ovoj studiji pokazuju da postoje situacije u kojima je potrebno uzeti u obzir neuniformnost raspodele temperature po uzorku, odnosno da pojednostavljenje modela korišćenjem uniformne raspodele dovodi do neprihvatljivih grešaka.
AB  - This paper investigates the influence of temperature field non-uniformity on sintering simulation results using the Skorohod-Olevsky viscous sintering model. As a difference to previous studies, here a thermal transient analysis is performed to provide a detailed temperature field over the component within sintering time. Results obtained using uniform temperature distribution are compared to those obtained using a nonuniform distribution derived from a transient thermal analysis. Results are compared for different geometry sizes, that lead to different temperature non-uniformity levels. The study has shown that the temperature nonuniformity cannot always be neglected and should be considered as a possible source of modeling error.
PB  - Univerzitet u Beogradu - Mašinski fakultet, Beograd
T2  - FME Transactions
T1  - Osetljivost skorohodolevski viskoznog modela sinterovanja na promenu temperaturnog polje po uzorku u toku sinterovanja
T1  - Skorohod-Olevsky viscous sintering model sensitivity to temperature distribution during the sintering process
EP  - 725
IS  - 3
SP  - 719
VL  - 49
DO  - 10.5937/fme2103719P
ER  - 

@article{
author = "Petrović, Veljko M. and Buljak, Vladimir and Cornaggia, Aram",
year = "2021",
abstract = "U ovom radu proučavan je uticaj neuniformnosti temperaturnog polja po uzorku na rezultate simulacije procesa sinterovanja. Kao konstitutivni model ponašanja materijala upotrebljen je modifikovan fenomenološki Skorohod-Olevski viskozni model sinterovanja. Poređeni su rezultati simulacije dobijeni korišćenjem uniformne raspodele temperature, sa rezultatima koji koriste temperaturno polje dobijeno simulacijom zagrevanj auzorka. Poređenja se odnose na uzorke različiti hveličina, kako bi se ispitao različiti nivo neuniformnosti. Dobijeni rezultati u ovoj studiji pokazuju da postoje situacije u kojima je potrebno uzeti u obzir neuniformnost raspodele temperature po uzorku, odnosno da pojednostavljenje modela korišćenjem uniformne raspodele dovodi do neprihvatljivih grešaka., This paper investigates the influence of temperature field non-uniformity on sintering simulation results using the Skorohod-Olevsky viscous sintering model. As a difference to previous studies, here a thermal transient analysis is performed to provide a detailed temperature field over the component within sintering time. Results obtained using uniform temperature distribution are compared to those obtained using a nonuniform distribution derived from a transient thermal analysis. Results are compared for different geometry sizes, that lead to different temperature non-uniformity levels. The study has shown that the temperature nonuniformity cannot always be neglected and should be considered as a possible source of modeling error.",
publisher = "Univerzitet u Beogradu - Mašinski fakultet, Beograd",
journal = "FME Transactions",
title = "Osetljivost skorohodolevski viskoznog modela sinterovanja na promenu temperaturnog polje po uzorku u toku sinterovanja, Skorohod-Olevsky viscous sintering model sensitivity to temperature distribution during the sintering process",
pages = "725-719",
number = "3",
volume = "49",
doi = "10.5937/fme2103719P"
}

Petrović, V. M., Buljak, V.,& Cornaggia, A.. (2021). Osetljivost skorohodolevski viskoznog modela sinterovanja na promenu temperaturnog polje po uzorku u toku sinterovanja. in FME Transactions
Univerzitet u Beogradu - Mašinski fakultet, Beograd., 49(3), 719-725.
https://doi.org/10.5937/fme2103719P

Petrović VM, Buljak V, Cornaggia A. Osetljivost skorohodolevski viskoznog modela sinterovanja na promenu temperaturnog polje po uzorku u toku sinterovanja. in FME Transactions. 2021;49(3):719-725.
doi:10.5937/fme2103719P .

Petrović, Veljko M., Buljak, Vladimir, Cornaggia, Aram, "Osetljivost skorohodolevski viskoznog modela sinterovanja na promenu temperaturnog polje po uzorku u toku sinterovanja" in FME Transactions, 49, no. 3 (2021):719-725,
https://doi.org/10.5937/fme2103719P . .

TY  - JOUR
AU  - Buljak, Vladimir
AU  - Baivier-Romero, Severine
AU  - Kallel, Achraf
PY  - 2021
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/3542
AB  - Phenomenological plasticity models that relate relative density to plastic strain are frequently used to simulate ceramic powder compaction. With respect to the form implemented in finite element codes, they need to be modified in order to define governing parameters as functions of relative densities. Such a modification increases the number of constitutive parameters and makes their calibration a demanding task that involves a large number of experiments. The novel calibration procedure investigated in this paper is based on inverse analysis methodology, centered on the minimization of a discrepancy function that quantifies the difference between experimentally measured and numerically computed quantities. In order to capture the influence of sought parameters on measured quantities, three different geometries of die and punches are proposed, resulting from a sensitivity analysis performed using numerical simulations of the test. The formulated calibration protocol requires only data that can be collected during the compaction test and, thus, involves a relatively smaller number of experiments. The developed procedure is tested on an alumina powder mixture, used for refractory products, by making a reference to the modified Drucker-Prager Cap model. The assessed parameters are compared to reference values, obtained through more laborious destructive tests performed on green bodies, and are further used to simulate the compaction test with arbitrary geometries. Both comparisons evidenced excellent agreement.
PB  - MDPI, Basel
T2  - Materials
T1  - Calibration of Drucker-Prager Cap Constitutive Model for Ceramic Powder Compaction through Inverse Analysis
IS  - 14
VL  - 14
DO  - 10.3390/ma14144044
ER  - 

@article{
author = "Buljak, Vladimir and Baivier-Romero, Severine and Kallel, Achraf",
year = "2021",
abstract = "Phenomenological plasticity models that relate relative density to plastic strain are frequently used to simulate ceramic powder compaction. With respect to the form implemented in finite element codes, they need to be modified in order to define governing parameters as functions of relative densities. Such a modification increases the number of constitutive parameters and makes their calibration a demanding task that involves a large number of experiments. The novel calibration procedure investigated in this paper is based on inverse analysis methodology, centered on the minimization of a discrepancy function that quantifies the difference between experimentally measured and numerically computed quantities. In order to capture the influence of sought parameters on measured quantities, three different geometries of die and punches are proposed, resulting from a sensitivity analysis performed using numerical simulations of the test. The formulated calibration protocol requires only data that can be collected during the compaction test and, thus, involves a relatively smaller number of experiments. The developed procedure is tested on an alumina powder mixture, used for refractory products, by making a reference to the modified Drucker-Prager Cap model. The assessed parameters are compared to reference values, obtained through more laborious destructive tests performed on green bodies, and are further used to simulate the compaction test with arbitrary geometries. Both comparisons evidenced excellent agreement.",
publisher = "MDPI, Basel",
journal = "Materials",
title = "Calibration of Drucker-Prager Cap Constitutive Model for Ceramic Powder Compaction through Inverse Analysis",
number = "14",
volume = "14",
doi = "10.3390/ma14144044"
}

Buljak, V., Baivier-Romero, S.,& Kallel, A.. (2021). Calibration of Drucker-Prager Cap Constitutive Model for Ceramic Powder Compaction through Inverse Analysis. in Materials
MDPI, Basel., 14(14).
https://doi.org/10.3390/ma14144044

Buljak V, Baivier-Romero S, Kallel A. Calibration of Drucker-Prager Cap Constitutive Model for Ceramic Powder Compaction through Inverse Analysis. in Materials. 2021;14(14).
doi:10.3390/ma14144044 .

Buljak, Vladimir, Baivier-Romero, Severine, Kallel, Achraf, "Calibration of Drucker-Prager Cap Constitutive Model for Ceramic Powder Compaction through Inverse Analysis" in Materials, 14, no. 14 (2021),
https://doi.org/10.3390/ma14144044 . .

TY  - BOOK
AU  - Buljak, Vladimir
AU  - Ranzi, G.
PY  - 2021
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/3651
AB  - Constitutive Modeling of Engineering Materials provides an extensive theoretical overview of elastic, plastic, damage, and fracture models, giving readers the foundational knowledge needed to successfully apply them to and solve common engineering material problems. Particular attention is given to inverse analysis, parameter identification, and the numerical implementation of models with the finite element method. Application in practice is discussed in detail, showing examples of working computer programs for simple constitutive behaviors. Examples explore the important components of material modeling which form the building blocks of any complex constitutive behavior.
PB  - Elsevier
T2  - Constitutive Modeling of Engineering Materials: Theory, Computer Implementation, and Parameter Ident
T1  - Constitutive Modeling of Engineering Materials: Theory, Computer Implementation, and Parameter Identification
EP  - 317
SP  - 1
DO  - 10.1016/B978-0-12-814696-5.00002-2
ER  - 

@book{
author = "Buljak, Vladimir and Ranzi, G.",
year = "2021",
abstract = "Constitutive Modeling of Engineering Materials provides an extensive theoretical overview of elastic, plastic, damage, and fracture models, giving readers the foundational knowledge needed to successfully apply them to and solve common engineering material problems. Particular attention is given to inverse analysis, parameter identification, and the numerical implementation of models with the finite element method. Application in practice is discussed in detail, showing examples of working computer programs for simple constitutive behaviors. Examples explore the important components of material modeling which form the building blocks of any complex constitutive behavior.",
publisher = "Elsevier",
journal = "Constitutive Modeling of Engineering Materials: Theory, Computer Implementation, and Parameter Ident",
title = "Constitutive Modeling of Engineering Materials: Theory, Computer Implementation, and Parameter Identification",
pages = "317-1",
doi = "10.1016/B978-0-12-814696-5.00002-2"
}

Buljak, V.,& Ranzi, G.. (2021). Constitutive Modeling of Engineering Materials: Theory, Computer Implementation, and Parameter Identification. in Constitutive Modeling of Engineering Materials: Theory, Computer Implementation, and Parameter Ident
Elsevier., 1-317.
https://doi.org/10.1016/B978-0-12-814696-5.00002-2

Buljak V, Ranzi G. Constitutive Modeling of Engineering Materials: Theory, Computer Implementation, and Parameter Identification. in Constitutive Modeling of Engineering Materials: Theory, Computer Implementation, and Parameter Ident. 2021;:1-317.
doi:10.1016/B978-0-12-814696-5.00002-2 .

Buljak, Vladimir, Ranzi, G., "Constitutive Modeling of Engineering Materials: Theory, Computer Implementation, and Parameter Identification" in Constitutive Modeling of Engineering Materials: Theory, Computer Implementation, and Parameter Ident (2021):1-317,
https://doi.org/10.1016/B978-0-12-814696-5.00002-2 . .

TY  - CONF
AU  - Aranđelović, Nevena
AU  - Buljak, Vladimir
PY  - 2019
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/4639
AB  - As stent technology moves forward, there’s a growing need for fast and accurate stent
deployment visualizations. To that end, the Finite Element Method was used for quasi-static
analysis of a balloon expandable stent. A model was created, which includes a stent, balloon,
artery and a plaque. In order to achieve faster computation, various approximations have been
included, especially considering the balloon, artery and plaque. Some non-linear problems are
assessed, like the contact between different parts of the model. Arterial tissue and plaque are
modeled as isotropic hyperelastic materials. The balloon was specially designed and discretized to avoid the computational difficulties during inflation. Thanks to the complexity of this model,
useful results can be obtained in a reasonable time frame. The software used for FEM analysis
was ABAQUS.
PB  - Beograd : Srpsko društvo za mehaniku
C3  - Proceeding of 7th International Congress of Serbian Society of Mechanics Sremski Karlovci, Serbia, June 24-26, 2019.
T1  - FEM ANALYSIS OF CORONARY STENT DEPLOYMENT
UR  - https://hdl.handle.net/21.15107/rcub_machinery_4639
ER  - 

@conference{
author = "Aranđelović, Nevena and Buljak, Vladimir",
year = "2019",
abstract = "As stent technology moves forward, there’s a growing need for fast and accurate stent
deployment visualizations. To that end, the Finite Element Method was used for quasi-static
analysis of a balloon expandable stent. A model was created, which includes a stent, balloon,
artery and a plaque. In order to achieve faster computation, various approximations have been
included, especially considering the balloon, artery and plaque. Some non-linear problems are
assessed, like the contact between different parts of the model. Arterial tissue and plaque are
modeled as isotropic hyperelastic materials. The balloon was specially designed and discretized to avoid the computational difficulties during inflation. Thanks to the complexity of this model,
useful results can be obtained in a reasonable time frame. The software used for FEM analysis
was ABAQUS.",
publisher = "Beograd : Srpsko društvo za mehaniku",
journal = "Proceeding of 7th International Congress of Serbian Society of Mechanics Sremski Karlovci, Serbia, June 24-26, 2019.",
title = "FEM ANALYSIS OF CORONARY STENT DEPLOYMENT",
url = "https://hdl.handle.net/21.15107/rcub_machinery_4639"
}

Aranđelović, N.,& Buljak, V.. (2019). FEM ANALYSIS OF CORONARY STENT DEPLOYMENT. in Proceeding of 7th International Congress of Serbian Society of Mechanics Sremski Karlovci, Serbia, June 24-26, 2019.
Beograd : Srpsko društvo za mehaniku..
https://hdl.handle.net/21.15107/rcub_machinery_4639

Aranđelović N, Buljak V. FEM ANALYSIS OF CORONARY STENT DEPLOYMENT. in Proceeding of 7th International Congress of Serbian Society of Mechanics Sremski Karlovci, Serbia, June 24-26, 2019.. 2019;.
https://hdl.handle.net/21.15107/rcub_machinery_4639 .

Aranđelović, Nevena, Buljak, Vladimir, "FEM ANALYSIS OF CORONARY STENT DEPLOYMENT" in Proceeding of 7th International Congress of Serbian Society of Mechanics Sremski Karlovci, Serbia, June 24-26, 2019. (2019),
https://hdl.handle.net/21.15107/rcub_machinery_4639 .

TY  - JOUR
AU  - Obradović, Nina
AU  - Fahrenholtz, William G.
AU  - Filipović, Suzana
AU  - Corlett, Cole
AU  - Đorđević, Pavle
AU  - Rogan, Jelena
AU  - Vulić, Predrag J.
AU  - Buljak, Vladimir
AU  - Pavlović, Vladimir B.
PY  - 2019
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/3235
AB  - Single phase MgAl2O4 was made from a one-to-one molar ratio of MgO and Al2O3 powders mixed using ball-milling. Mixtures of MgO and Al2O3 were subsequently treated in planetary ball mill for 30, 60, 90 and 120 minutes in air. The aim of this study was to examine phase composition, microstructure, and densification behavior of sintered specimens. After sintering in dilatometer at 1500 degrees C, the powder was converted to single phase MgAl2O4. The results show that mechanical activation improved the densification behavior of MgAl2O4 sintered specimens, and it reduced the onset temperature for sintering by approx. 100 degrees C. Based on dilatometer data, powders were subsequently densified at 1450 degrees C by hot pressing. Almost all specimens exhibited full density, while sample activated for 30 minutes showed the fastest densification rate.
PB  - Međunarodni Institut za nauku o sinterovanju, Beograd
T2  - Science of Sintering
T1  - Characterization of MgAl2O4 Sintered Ceramics
EP  - 376
IS  - 4
SP  - 363
VL  - 51
DO  - 10.2298/SOS1904363O
ER  - 

@article{
author = "Obradović, Nina and Fahrenholtz, William G. and Filipović, Suzana and Corlett, Cole and Đorđević, Pavle and Rogan, Jelena and Vulić, Predrag J. and Buljak, Vladimir and Pavlović, Vladimir B.",
year = "2019",
abstract = "Single phase MgAl2O4 was made from a one-to-one molar ratio of MgO and Al2O3 powders mixed using ball-milling. Mixtures of MgO and Al2O3 were subsequently treated in planetary ball mill for 30, 60, 90 and 120 minutes in air. The aim of this study was to examine phase composition, microstructure, and densification behavior of sintered specimens. After sintering in dilatometer at 1500 degrees C, the powder was converted to single phase MgAl2O4. The results show that mechanical activation improved the densification behavior of MgAl2O4 sintered specimens, and it reduced the onset temperature for sintering by approx. 100 degrees C. Based on dilatometer data, powders were subsequently densified at 1450 degrees C by hot pressing. Almost all specimens exhibited full density, while sample activated for 30 minutes showed the fastest densification rate.",
publisher = "Međunarodni Institut za nauku o sinterovanju, Beograd",
journal = "Science of Sintering",
title = "Characterization of MgAl2O4 Sintered Ceramics",
pages = "376-363",
number = "4",
volume = "51",
doi = "10.2298/SOS1904363O"
}

Obradović, N., Fahrenholtz, W. G., Filipović, S., Corlett, C., Đorđević, P., Rogan, J., Vulić, P. J., Buljak, V.,& Pavlović, V. B.. (2019). Characterization of MgAl2O4 Sintered Ceramics. in Science of Sintering
Međunarodni Institut za nauku o sinterovanju, Beograd., 51(4), 363-376.
https://doi.org/10.2298/SOS1904363O

Obradović N, Fahrenholtz WG, Filipović S, Corlett C, Đorđević P, Rogan J, Vulić PJ, Buljak V, Pavlović VB. Characterization of MgAl2O4 Sintered Ceramics. in Science of Sintering. 2019;51(4):363-376.
doi:10.2298/SOS1904363O .

Obradović, Nina, Fahrenholtz, William G., Filipović, Suzana, Corlett, Cole, Đorđević, Pavle, Rogan, Jelena, Vulić, Predrag J., Buljak, Vladimir, Pavlović, Vladimir B., "Characterization of MgAl2O4 Sintered Ceramics" in Science of Sintering, 51, no. 4 (2019):363-376,
https://doi.org/10.2298/SOS1904363O . .

TY  - JOUR
AU  - Buljak, Vladimir
AU  - Oesch, Tyler
AU  - Bruno, Giovanni
PY  - 2019
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/3087
AB  - The main hindrance to realistic models of fiber-reinforced concrete (FRC) is the local materials property variation, which does not yet reliably allow simulations at the structural level. The idea presented in this paper makes use of an existing constitutive model, but resolves the problem of localized material variation through X-ray computed tomography (CT)-based pre-processing. First, a three-point bending test of a notched beam is considered, where pre-test fiber orientations are measured using CT. A numerical model is then built with the zone subjected to progressive damage, modeled using an orthotropic damage model. To each of the finite elements within this zone, a local coordinate system is assigned, with its longitudinal direction defined by local fiber orientations. Second, the parameters of the constitutive damage model are determined through inverse analysis using load-displacement data obtained from the test. These parameters are considered to clearly explain the material behavior for any arbitrary external action and fiber orientation, for the same geometrical properties and volumetric ratio of fibers. Third, the effectiveness of the resulting model is demonstrated using a second, control experiment. The results of the control experiment analyzed in this research compare well with the model results. The ultimate strength was predicted with an error of about 6%, while the work-of-load was predicted within 4%. It demonstrates the potential of this method for accurately predicting the mechanical performance of FRC components.
PB  - MDPI, Basel
T2  - Materials
T1  - Simulating Fiber-Reinforced Concrete Mechanical Performance Using CT-Based Fiber Orientation Data
IS  - 5
VL  - 12
DO  - 10.3390/ma12050717
ER  - 

@article{
author = "Buljak, Vladimir and Oesch, Tyler and Bruno, Giovanni",
year = "2019",
abstract = "The main hindrance to realistic models of fiber-reinforced concrete (FRC) is the local materials property variation, which does not yet reliably allow simulations at the structural level. The idea presented in this paper makes use of an existing constitutive model, but resolves the problem of localized material variation through X-ray computed tomography (CT)-based pre-processing. First, a three-point bending test of a notched beam is considered, where pre-test fiber orientations are measured using CT. A numerical model is then built with the zone subjected to progressive damage, modeled using an orthotropic damage model. To each of the finite elements within this zone, a local coordinate system is assigned, with its longitudinal direction defined by local fiber orientations. Second, the parameters of the constitutive damage model are determined through inverse analysis using load-displacement data obtained from the test. These parameters are considered to clearly explain the material behavior for any arbitrary external action and fiber orientation, for the same geometrical properties and volumetric ratio of fibers. Third, the effectiveness of the resulting model is demonstrated using a second, control experiment. The results of the control experiment analyzed in this research compare well with the model results. The ultimate strength was predicted with an error of about 6%, while the work-of-load was predicted within 4%. It demonstrates the potential of this method for accurately predicting the mechanical performance of FRC components.",
publisher = "MDPI, Basel",
journal = "Materials",
title = "Simulating Fiber-Reinforced Concrete Mechanical Performance Using CT-Based Fiber Orientation Data",
number = "5",
volume = "12",
doi = "10.3390/ma12050717"
}

Buljak, V., Oesch, T.,& Bruno, G.. (2019). Simulating Fiber-Reinforced Concrete Mechanical Performance Using CT-Based Fiber Orientation Data. in Materials
MDPI, Basel., 12(5).
https://doi.org/10.3390/ma12050717

Buljak V, Oesch T, Bruno G. Simulating Fiber-Reinforced Concrete Mechanical Performance Using CT-Based Fiber Orientation Data. in Materials. 2019;12(5).
doi:10.3390/ma12050717 .

Buljak, Vladimir, Oesch, Tyler, Bruno, Giovanni, "Simulating Fiber-Reinforced Concrete Mechanical Performance Using CT-Based Fiber Orientation Data" in Materials, 12, no. 5 (2019),
https://doi.org/10.3390/ma12050717 . .

TY  - JOUR
AU  - Buljak, Vladimir
AU  - Bruno, Giovanni
PY  - 2018
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2745
AB  - A numerical framework is developed to study the hysteresis of elastic properties of porous ceramics as a function of temperature. The developed numerical model is capable of employing experimentally measured crystallographic orientation distribution and coefficient of thermal expansion values. For realistic modeling of the microstructure, Voronoi polygons are used to generate polycrystalline grains. Some grains are considered as voids, to simulate the material porosity. To model intercrystalline cracking, cohesive elements are inserted along grain boundaries. Crack healing (recovery of the initial properties) upon closure is taken into account with special cohesive elements implemented in the commercial code ABAQUS. The numerical model can be used to estimate fracture properties governing the cohesive behavior through inverse analysis procedure. The model is applied to a porous cordierite ceramic. The obtained fracture properties are further used to successfully simulate general non-linear macroscopic stress-strain curves of cordierite, thereby validating the model.
PB  - Elsevier Sci Ltd, Oxford
T2  - Journal of The European Ceramic Society
T1  - Numerical modeling of thermally induced microcracking in porous ceramics: An approach using cohesive elements
EP  - 4108
IS  - 11
SP  - 4099
VL  - 38
DO  - 10.1016/j.jeurceramsoc.2018.03.041
ER  - 

@article{
author = "Buljak, Vladimir and Bruno, Giovanni",
year = "2018",
abstract = "A numerical framework is developed to study the hysteresis of elastic properties of porous ceramics as a function of temperature. The developed numerical model is capable of employing experimentally measured crystallographic orientation distribution and coefficient of thermal expansion values. For realistic modeling of the microstructure, Voronoi polygons are used to generate polycrystalline grains. Some grains are considered as voids, to simulate the material porosity. To model intercrystalline cracking, cohesive elements are inserted along grain boundaries. Crack healing (recovery of the initial properties) upon closure is taken into account with special cohesive elements implemented in the commercial code ABAQUS. The numerical model can be used to estimate fracture properties governing the cohesive behavior through inverse analysis procedure. The model is applied to a porous cordierite ceramic. The obtained fracture properties are further used to successfully simulate general non-linear macroscopic stress-strain curves of cordierite, thereby validating the model.",
publisher = "Elsevier Sci Ltd, Oxford",
journal = "Journal of The European Ceramic Society",
title = "Numerical modeling of thermally induced microcracking in porous ceramics: An approach using cohesive elements",
pages = "4108-4099",
number = "11",
volume = "38",
doi = "10.1016/j.jeurceramsoc.2018.03.041"
}

Buljak, V.,& Bruno, G.. (2018). Numerical modeling of thermally induced microcracking in porous ceramics: An approach using cohesive elements. in Journal of The European Ceramic Society
Elsevier Sci Ltd, Oxford., 38(11), 4099-4108.
https://doi.org/10.1016/j.jeurceramsoc.2018.03.041

Buljak V, Bruno G. Numerical modeling of thermally induced microcracking in porous ceramics: An approach using cohesive elements. in Journal of The European Ceramic Society. 2018;38(11):4099-4108.
doi:10.1016/j.jeurceramsoc.2018.03.041 .

Buljak, Vladimir, Bruno, Giovanni, "Numerical modeling of thermally induced microcracking in porous ceramics: An approach using cohesive elements" in Journal of The European Ceramic Society, 38, no. 11 (2018):4099-4108,
https://doi.org/10.1016/j.jeurceramsoc.2018.03.041 . .

TY  - JOUR
AU  - Buljak, Vladimir
AU  - Cocchetti, Giuseppe
AU  - Cornaggia, Aram
AU  - Maier, Giulio
PY  - 2018
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2895
AB  - Small Punch Tests (SPT) are, at present, frequently employed for diagnostic analyses of metallic structural components and are considered in codes of practice because the damage generated by miniature specimen extraction is small (quasi-non-destructive tests). This paper contains a description of the following contributions for improvement in the state-of-the-art of SPT practice: assessment of material parameters through inverse analysis, made faster and more economical by employing model reduction through a Proper Orthogonal Decomposition (POD) procedure. The methodology is developed to assess material parameters entering into diverse constitutive models, thus resulting in a more flexible identification framework, capable of addressing different kinds of material behaviour. Within the paper, real experimental data are used and comparisons of computed stress-strain curves with experimentally measured ones, through typical tensile tests, show an excellent agreement.
PB  - Springer, Dordrecht
T2  - Meccanica
T1  - Parameter identification in elastoplastic material models by Small Punch Tests and inverse analysis with model reduction
EP  - 3829
IS  - 15
SP  - 3815
VL  - 53
DO  - 10.1007/s11012-018-0914-3
ER  - 

@article{
author = "Buljak, Vladimir and Cocchetti, Giuseppe and Cornaggia, Aram and Maier, Giulio",
year = "2018",
abstract = "Small Punch Tests (SPT) are, at present, frequently employed for diagnostic analyses of metallic structural components and are considered in codes of practice because the damage generated by miniature specimen extraction is small (quasi-non-destructive tests). This paper contains a description of the following contributions for improvement in the state-of-the-art of SPT practice: assessment of material parameters through inverse analysis, made faster and more economical by employing model reduction through a Proper Orthogonal Decomposition (POD) procedure. The methodology is developed to assess material parameters entering into diverse constitutive models, thus resulting in a more flexible identification framework, capable of addressing different kinds of material behaviour. Within the paper, real experimental data are used and comparisons of computed stress-strain curves with experimentally measured ones, through typical tensile tests, show an excellent agreement.",
publisher = "Springer, Dordrecht",
journal = "Meccanica",
title = "Parameter identification in elastoplastic material models by Small Punch Tests and inverse analysis with model reduction",
pages = "3829-3815",
number = "15",
volume = "53",
doi = "10.1007/s11012-018-0914-3"
}

Buljak, V., Cocchetti, G., Cornaggia, A.,& Maier, G.. (2018). Parameter identification in elastoplastic material models by Small Punch Tests and inverse analysis with model reduction. in Meccanica
Springer, Dordrecht., 53(15), 3815-3829.
https://doi.org/10.1007/s11012-018-0914-3

Buljak V, Cocchetti G, Cornaggia A, Maier G. Parameter identification in elastoplastic material models by Small Punch Tests and inverse analysis with model reduction. in Meccanica. 2018;53(15):3815-3829.
doi:10.1007/s11012-018-0914-3 .

Buljak, Vladimir, Cocchetti, Giuseppe, Cornaggia, Aram, Maier, Giulio, "Parameter identification in elastoplastic material models by Small Punch Tests and inverse analysis with model reduction" in Meccanica, 53, no. 15 (2018):3815-3829,
https://doi.org/10.1007/s11012-018-0914-3 . .

TY  - JOUR
AU  - Pandey, Shwetank
AU  - Buljak, Vladimir
AU  - Balać, Igor
PY  - 2017
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2523
AB  - Numerical simulations of different ceramic production phases often involve complex constitutive models, with difficult calibration process, relying on a large number of experiments. Methodological developments, proposed in present paper regarding this calibration problem can be outlined as follows: assessment of constitutive parameters is performed through inverse analysis procedure, centered on minimization of discrepancy function which quantifies the difference between measurable quantities and their computed counterpart. Resulting minimization problem is solved through genetic algorithms, while the computational burden is made consistent with constraints of routine industrial applications by exploiting Reduced Order Model (ROM) based on proper orthogonal decomposition. Throughout minimization, a gradual enrichment of designed ROM is used, by including additional simulations. Such strategy turned out to be beneficial when applied to models with a large number of parameters. Developed procedure seems to be effective when dealing with complex constitutive models, that can give rise to non-continuous discrepancy function due to the numerical instabilities. Proposed approach is tested and experimentally validated on the calibration of modified Drucker-Prager CAP model, frequently adopted for ceramic powder pressing simulations. Assessed values are compared with those obtained by traditional, time-consuming tests, performed on pressed green bodies.
PB  - Međunarodni Institut za nauku o sinterovanju, Beograd
T2  - Science of Sintering
T1  - Reduced Order Numerical Modeling for Calibration of Complex Constitutive Models in Powder Pressing Simulations
EP  - 345
IS  - 3
SP  - 331
VL  - 49
DO  - 10.2298/SOS1703331P
ER  - 

@article{
author = "Pandey, Shwetank and Buljak, Vladimir and Balać, Igor",
year = "2017",
abstract = "Numerical simulations of different ceramic production phases often involve complex constitutive models, with difficult calibration process, relying on a large number of experiments. Methodological developments, proposed in present paper regarding this calibration problem can be outlined as follows: assessment of constitutive parameters is performed through inverse analysis procedure, centered on minimization of discrepancy function which quantifies the difference between measurable quantities and their computed counterpart. Resulting minimization problem is solved through genetic algorithms, while the computational burden is made consistent with constraints of routine industrial applications by exploiting Reduced Order Model (ROM) based on proper orthogonal decomposition. Throughout minimization, a gradual enrichment of designed ROM is used, by including additional simulations. Such strategy turned out to be beneficial when applied to models with a large number of parameters. Developed procedure seems to be effective when dealing with complex constitutive models, that can give rise to non-continuous discrepancy function due to the numerical instabilities. Proposed approach is tested and experimentally validated on the calibration of modified Drucker-Prager CAP model, frequently adopted for ceramic powder pressing simulations. Assessed values are compared with those obtained by traditional, time-consuming tests, performed on pressed green bodies.",
publisher = "Međunarodni Institut za nauku o sinterovanju, Beograd",
journal = "Science of Sintering",
title = "Reduced Order Numerical Modeling for Calibration of Complex Constitutive Models in Powder Pressing Simulations",
pages = "345-331",
number = "3",
volume = "49",
doi = "10.2298/SOS1703331P"
}

Pandey, S., Buljak, V.,& Balać, I.. (2017). Reduced Order Numerical Modeling for Calibration of Complex Constitutive Models in Powder Pressing Simulations. in Science of Sintering
Međunarodni Institut za nauku o sinterovanju, Beograd., 49(3), 331-345.
https://doi.org/10.2298/SOS1703331P

Pandey S, Buljak V, Balać I. Reduced Order Numerical Modeling for Calibration of Complex Constitutive Models in Powder Pressing Simulations. in Science of Sintering. 2017;49(3):331-345.
doi:10.2298/SOS1703331P .

Pandey, Shwetank, Buljak, Vladimir, Balać, Igor, "Reduced Order Numerical Modeling for Calibration of Complex Constitutive Models in Powder Pressing Simulations" in Science of Sintering, 49, no. 3 (2017):331-345,
https://doi.org/10.2298/SOS1703331P . .

TY  - JOUR
AU  - Buljak, Vladimir
AU  - Cocchetti, Giuseppe
AU  - Cornaggia, Aram
AU  - Maier, Giulio
PY  - 2017
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2520
AB  - "Small Punch"" (SP) tests, at present frequently employed for mechanical characterizations of structural metals, particularly for diagnosis of plant components, are here considered in view of employment also for assessments of stresses. In the procedure proposed herein the standardised sample removal from an in-service component for SP tests is exploited as external action altering the residual stress state possibly present near to the surface in the location considered. Full-field measurements of consequent displacements in the surrounding surface are employed as input for inverse analysis based on the following features: computer simulations of the sample removal as for its consequences due to relaxation of the preexisting stress state; "non-uniformity" of residual-stress dependence on depth described as layer dependent with uniformity in each layer of a pre-defined set of layers; "discrepancy function" minimization with employment of the elasticity parameters provided by the subsequent SP test. The advantages of the novel method consist of no-more need of traditional usual "Hole Drilling" (HD) tests or other tests for residual-stress estimation. The SP experimental procedure proposed herein for estimations of both stress state and elastic-plastic material properties would imply reductions of damages, costs and times in structural diagnoses.
PB  - Elsevier Sci Ltd, Oxford
T2  - Engineering Structures
T1  - Estimation of residual stresses by inverse analysis based on experimental data from sample removal for "small punch" tests
EP  - 86
SP  - 77
VL  - 136
DO  - 10.1016/j.engstruct.2016.12.062
ER  - 

@article{
author = "Buljak, Vladimir and Cocchetti, Giuseppe and Cornaggia, Aram and Maier, Giulio",
year = "2017",
abstract = ""Small Punch"" (SP) tests, at present frequently employed for mechanical characterizations of structural metals, particularly for diagnosis of plant components, are here considered in view of employment also for assessments of stresses. In the procedure proposed herein the standardised sample removal from an in-service component for SP tests is exploited as external action altering the residual stress state possibly present near to the surface in the location considered. Full-field measurements of consequent displacements in the surrounding surface are employed as input for inverse analysis based on the following features: computer simulations of the sample removal as for its consequences due to relaxation of the preexisting stress state; "non-uniformity" of residual-stress dependence on depth described as layer dependent with uniformity in each layer of a pre-defined set of layers; "discrepancy function" minimization with employment of the elasticity parameters provided by the subsequent SP test. The advantages of the novel method consist of no-more need of traditional usual "Hole Drilling" (HD) tests or other tests for residual-stress estimation. The SP experimental procedure proposed herein for estimations of both stress state and elastic-plastic material properties would imply reductions of damages, costs and times in structural diagnoses.",
publisher = "Elsevier Sci Ltd, Oxford",
journal = "Engineering Structures",
title = "Estimation of residual stresses by inverse analysis based on experimental data from sample removal for "small punch" tests",
pages = "86-77",
volume = "136",
doi = "10.1016/j.engstruct.2016.12.062"
}

Buljak, V., Cocchetti, G., Cornaggia, A.,& Maier, G.. (2017). Estimation of residual stresses by inverse analysis based on experimental data from sample removal for "small punch" tests. in Engineering Structures
Elsevier Sci Ltd, Oxford., 136, 77-86.
https://doi.org/10.1016/j.engstruct.2016.12.062

Buljak V, Cocchetti G, Cornaggia A, Maier G. Estimation of residual stresses by inverse analysis based on experimental data from sample removal for "small punch" tests. in Engineering Structures. 2017;136:77-86.
doi:10.1016/j.engstruct.2016.12.062 .

Buljak, Vladimir, Cocchetti, Giuseppe, Cornaggia, Aram, Maier, Giulio, "Estimation of residual stresses by inverse analysis based on experimental data from sample removal for "small punch" tests" in Engineering Structures, 136 (2017):77-86,
https://doi.org/10.1016/j.engstruct.2016.12.062 . .

TY  - JOUR
AU  - Buljak, Vladimir
AU  - Pandey, Shwetank
AU  - Balać, Igor
PY  - 2017
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2531
AB  - Eksperiment instrumentalnog utiskivanja se sve više koristi za karakterizaciju materijala različitog tipa. Razvijene metode kombinuju ovaj test sa kompjuterskom simulacijom u okviru inverznih analiza sa ciljem dobijanja parametara koji ulaze u jednačine različitih konstitutivnih modela. Izlaz iz ovakvih procedura predstavljaju vrednosti traženih parametara u determinističkom smislu, dok je za praktičnu inženjersku upotrebu poželjno raspolagati i sa procenom tačnosti dobijenih vrednosti. U ovom radu prikazana je numeričko-eksperimentalna metoda zasnovana na inverznoj analizi koja kao ulazni podatak koristi eksperimentalno izmerenu krivu utiskivanja (kriva koja daje zavisnost primenjene sila u funkciji ostvarene dubine utiskivanja). Numeričke simulacije testa utiskivanja su značajno ubrzame primenom redukovanog modela zasnovanog na pravilnoj ortogonalnoj dekompoziciji a posebno razvijenom za ovu svrhu. Rezultijući inverzni problem je rešen u stohastičkom kontekstu korišćenjem Monte Karlo simulacija kao i Kalmanovih filtera. Dobijeni rezultati su komparativno prezentovani u cilju poređenja dobijene tačnosti i računarske efikasnosti.
AB  - Indentation test is used with growing popularity for the characterization of various materials on different scales. Developed methods are combining the test with computer simulation and inverse analyses to assess material parameters entering into constitutive models. The outputs of such procedures are expressed as evaluation of sought parameters in deterministic sense, while for engineering practice it is desirable to assess also the uncertainty which affects the final estimates resulting from various sources of errors within the identification procedure. In this paper an experimental-numerical method is presented centered on inverse analysis build upon data collected from the indentation test in the form of force-penetration relationship (so-called 'indentation curve'). Recursive simulations are made computationally economical by an 'a priori' model reduction procedure. Resulting inverse problem is solved in a stochastic context using Monte Carlo simulations and non-sequential Extended Kalman filter. Obtained results are presented comparatively as for accuracy and computational efficiency.
PB  - Univerzitet u Beogradu - Mašinski fakultet, Beograd
T2  - FME Transactions
T1  - Kalibrisanje konstitutivnih modela korišćenjem instrumentalnog utiskivanja i stohastičke inverzne analize
T1  - Material model calibration through indentation test and stochastic inverse analysis
EP  - 116
IS  - 1
SP  - 109
VL  - 45
DO  - 10.5937/fmet1701109B
ER  - 

@article{
author = "Buljak, Vladimir and Pandey, Shwetank and Balać, Igor",
year = "2017",
abstract = "Eksperiment instrumentalnog utiskivanja se sve više koristi za karakterizaciju materijala različitog tipa. Razvijene metode kombinuju ovaj test sa kompjuterskom simulacijom u okviru inverznih analiza sa ciljem dobijanja parametara koji ulaze u jednačine različitih konstitutivnih modela. Izlaz iz ovakvih procedura predstavljaju vrednosti traženih parametara u determinističkom smislu, dok je za praktičnu inženjersku upotrebu poželjno raspolagati i sa procenom tačnosti dobijenih vrednosti. U ovom radu prikazana je numeričko-eksperimentalna metoda zasnovana na inverznoj analizi koja kao ulazni podatak koristi eksperimentalno izmerenu krivu utiskivanja (kriva koja daje zavisnost primenjene sila u funkciji ostvarene dubine utiskivanja). Numeričke simulacije testa utiskivanja su značajno ubrzame primenom redukovanog modela zasnovanog na pravilnoj ortogonalnoj dekompoziciji a posebno razvijenom za ovu svrhu. Rezultijući inverzni problem je rešen u stohastičkom kontekstu korišćenjem Monte Karlo simulacija kao i Kalmanovih filtera. Dobijeni rezultati su komparativno prezentovani u cilju poređenja dobijene tačnosti i računarske efikasnosti., Indentation test is used with growing popularity for the characterization of various materials on different scales. Developed methods are combining the test with computer simulation and inverse analyses to assess material parameters entering into constitutive models. The outputs of such procedures are expressed as evaluation of sought parameters in deterministic sense, while for engineering practice it is desirable to assess also the uncertainty which affects the final estimates resulting from various sources of errors within the identification procedure. In this paper an experimental-numerical method is presented centered on inverse analysis build upon data collected from the indentation test in the form of force-penetration relationship (so-called 'indentation curve'). Recursive simulations are made computationally economical by an 'a priori' model reduction procedure. Resulting inverse problem is solved in a stochastic context using Monte Carlo simulations and non-sequential Extended Kalman filter. Obtained results are presented comparatively as for accuracy and computational efficiency.",
publisher = "Univerzitet u Beogradu - Mašinski fakultet, Beograd",
journal = "FME Transactions",
title = "Kalibrisanje konstitutivnih modela korišćenjem instrumentalnog utiskivanja i stohastičke inverzne analize, Material model calibration through indentation test and stochastic inverse analysis",
pages = "116-109",
number = "1",
volume = "45",
doi = "10.5937/fmet1701109B"
}

Buljak, V., Pandey, S.,& Balać, I.. (2017). Kalibrisanje konstitutivnih modela korišćenjem instrumentalnog utiskivanja i stohastičke inverzne analize. in FME Transactions
Univerzitet u Beogradu - Mašinski fakultet, Beograd., 45(1), 109-116.
https://doi.org/10.5937/fmet1701109B

Buljak V, Pandey S, Balać I. Kalibrisanje konstitutivnih modela korišćenjem instrumentalnog utiskivanja i stohastičke inverzne analize. in FME Transactions. 2017;45(1):109-116.
doi:10.5937/fmet1701109B .

Buljak, Vladimir, Pandey, Shwetank, Balać, Igor, "Kalibrisanje konstitutivnih modela korišćenjem instrumentalnog utiskivanja i stohastičke inverzne analize" in FME Transactions, 45, no. 1 (2017):109-116,
https://doi.org/10.5937/fmet1701109B . .

TY  - CHAP
AU  - Buljak, Vladimir
AU  - Cocchetti, Giuseppe
AU  - Cornaggia, Aram
AU  - Maier, Giulio
AU  - Novati, Giorgio
AU  - Garbowski, Tomasz
PY  - 2015
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2179
AB  - Mechanical damages in structures, in structural components of plants and in industrial products usually imply changes of parameters which have central roles in computational modelling apt to assess safety margins with respect to service loading. Such parameters may depend also on the production processes in industrial environments. In this chapter, the parameter identification methodology by inverse analyses is dealt with under the following limitations: experiments at macroscale level, deterministic approaches, statical external actions and time independence in material behaviours. Semiempirical approaches frequently adopted in codes of practice are not dealt with here. The inverse analysis methods outlined here are centered on computational simulations of tests (namely, direct analyses), sensitivity analyses for the optimal design of experiments, model reduction procedures and other provisions apt to make fast and economical the parameter estimation in engineering practice. The applications summarized here as examples concern structural diagnoses based on indentation tests, in situ diagnostic experiments on concrete dams and laboratory mechanical characterization of membranes and laminates.
PB  - Springer New York
T2  - Handbook of Damage Mechanics: Nano to Macro Scale for Materials and Structures
T1  - Materials mechanical characterizations and structural diagnoses by inverse analyses
EP  - 642
SP  - 619
DO  - 10.1007/978-1-4614-5589-9
ER  - 

@inbook{
author = "Buljak, Vladimir and Cocchetti, Giuseppe and Cornaggia, Aram and Maier, Giulio and Novati, Giorgio and Garbowski, Tomasz",
year = "2015",
abstract = "Mechanical damages in structures, in structural components of plants and in industrial products usually imply changes of parameters which have central roles in computational modelling apt to assess safety margins with respect to service loading. Such parameters may depend also on the production processes in industrial environments. In this chapter, the parameter identification methodology by inverse analyses is dealt with under the following limitations: experiments at macroscale level, deterministic approaches, statical external actions and time independence in material behaviours. Semiempirical approaches frequently adopted in codes of practice are not dealt with here. The inverse analysis methods outlined here are centered on computational simulations of tests (namely, direct analyses), sensitivity analyses for the optimal design of experiments, model reduction procedures and other provisions apt to make fast and economical the parameter estimation in engineering practice. The applications summarized here as examples concern structural diagnoses based on indentation tests, in situ diagnostic experiments on concrete dams and laboratory mechanical characterization of membranes and laminates.",
publisher = "Springer New York",
journal = "Handbook of Damage Mechanics: Nano to Macro Scale for Materials and Structures",
booktitle = "Materials mechanical characterizations and structural diagnoses by inverse analyses",
pages = "642-619",
doi = "10.1007/978-1-4614-5589-9"
}

Buljak, V., Cocchetti, G., Cornaggia, A., Maier, G., Novati, G.,& Garbowski, T.. (2015). Materials mechanical characterizations and structural diagnoses by inverse analyses. in Handbook of Damage Mechanics: Nano to Macro Scale for Materials and Structures
Springer New York., 619-642.
https://doi.org/10.1007/978-1-4614-5589-9

Buljak V, Cocchetti G, Cornaggia A, Maier G, Novati G, Garbowski T. Materials mechanical characterizations and structural diagnoses by inverse analyses. in Handbook of Damage Mechanics: Nano to Macro Scale for Materials and Structures. 2015;:619-642.
doi:10.1007/978-1-4614-5589-9 .

Buljak, Vladimir, Cocchetti, Giuseppe, Cornaggia, Aram, Maier, Giulio, Novati, Giorgio, Garbowski, Tomasz, "Materials mechanical characterizations and structural diagnoses by inverse analyses" in Handbook of Damage Mechanics: Nano to Macro Scale for Materials and Structures (2015):619-642,
https://doi.org/10.1007/978-1-4614-5589-9 . .

TY  - JOUR
AU  - Buljak, Vladimir
AU  - Cocchetti, Giuseppe
AU  - Cornaggia, Aram
AU  - Maier, Giulio
PY  - 2015
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2253
AB  - Hole Drilling (HD) tests are frequently employed as "quasi-non-destructive" experiments, for assessments of residual stresses in metallic components of power plants and of other industrial structures. With respect to the present broadly standardized HD method, the following methodological developments are proposed and computationally validated in this paper: assessments of elastic and plastic parameters by indentation exploiting the hole generated by HD tests; employment of "Digital Image Correlation" (DIC) for full-field displacement measurements, instead of the strain measurements by gauge "rosettes" usually adopted so far; transitions from experimental data to sought parameters by inverse analyses based on computer simulations of both tests and on minimizations of a "discrepancy function". Interactions between the two experiments are here investigated, besides the elastic parameters transition from indentation (IND) to HD test interpretation. The main advantage achievable by the procedure proposed herein is reduction of additional "damage" and cost due to usual experimental procedures for diagnosis of structural components (e.g. frequently adopted "small punch" experiments or laboratory tension tests).
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Mechanics Research Communications
T1  - Assessment of residual stresses and mechanical characterization of materials by "hole drilling" and indentation tests combined and by inverse analysis
EP  - 24
SP  - 18
VL  - 68
DO  - 10.1016/j.mechrescom.2015.02.003
ER  - 

@article{
author = "Buljak, Vladimir and Cocchetti, Giuseppe and Cornaggia, Aram and Maier, Giulio",
year = "2015",
abstract = "Hole Drilling (HD) tests are frequently employed as "quasi-non-destructive" experiments, for assessments of residual stresses in metallic components of power plants and of other industrial structures. With respect to the present broadly standardized HD method, the following methodological developments are proposed and computationally validated in this paper: assessments of elastic and plastic parameters by indentation exploiting the hole generated by HD tests; employment of "Digital Image Correlation" (DIC) for full-field displacement measurements, instead of the strain measurements by gauge "rosettes" usually adopted so far; transitions from experimental data to sought parameters by inverse analyses based on computer simulations of both tests and on minimizations of a "discrepancy function". Interactions between the two experiments are here investigated, besides the elastic parameters transition from indentation (IND) to HD test interpretation. The main advantage achievable by the procedure proposed herein is reduction of additional "damage" and cost due to usual experimental procedures for diagnosis of structural components (e.g. frequently adopted "small punch" experiments or laboratory tension tests).",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Mechanics Research Communications",
title = "Assessment of residual stresses and mechanical characterization of materials by "hole drilling" and indentation tests combined and by inverse analysis",
pages = "24-18",
volume = "68",
doi = "10.1016/j.mechrescom.2015.02.003"
}

Buljak, V., Cocchetti, G., Cornaggia, A.,& Maier, G.. (2015). Assessment of residual stresses and mechanical characterization of materials by "hole drilling" and indentation tests combined and by inverse analysis. in Mechanics Research Communications
Pergamon-Elsevier Science Ltd, Oxford., 68, 18-24.
https://doi.org/10.1016/j.mechrescom.2015.02.003

Buljak V, Cocchetti G, Cornaggia A, Maier G. Assessment of residual stresses and mechanical characterization of materials by "hole drilling" and indentation tests combined and by inverse analysis. in Mechanics Research Communications. 2015;68:18-24.
doi:10.1016/j.mechrescom.2015.02.003 .

Buljak, Vladimir, Cocchetti, Giuseppe, Cornaggia, Aram, Maier, Giulio, "Assessment of residual stresses and mechanical characterization of materials by "hole drilling" and indentation tests combined and by inverse analysis" in Mechanics Research Communications, 68 (2015):18-24,
https://doi.org/10.1016/j.mechrescom.2015.02.003 . .

TY  - CONF
AU  - Buljak, Vladimir
AU  - Garbowski, Tomasz
PY  - 2014
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2004
AB  - Model reduction techniques generate low-dimensional models to parametrize PDEs in order to allow for efficient evaluation of highly non-linear problems in many-query and real-time context. Computing time in these methods is divided into a time consuming "off-line" phase needed to "train" a surrogate model, which is further used in "on-line" phase providing accurate results in a much faster way. The accuracy of these methods is strictly connected to the number of points in which the system response is previously computed and on their distribution in a parameter space. For a given number of analysis decided to be "invested" for the design of surrogate model, the accuracy can be further improved by the adequate distribution of them in a parameter space. Two methods of robust samples distribution are proposed here. A first method is based on interactive nodes aimed to optimize the distribution of them. A second is based on an optimal Latin hypercube design. Both presented methods are flexible with respect to the number of nodes involved and they can provide uniform distribution for any arbitrary number of them. Furthermore, they allow also for taking into account different importance of divers parameters.
PB  - Taylor and Francis - Balkema
C3  - Recent Advances in Computational Mechanics - Proceedings of the 20th International Conference on Com
T1  - Efficient methods for optimal space filling in model reduction techniques
EP  - 291
SP  - 285
DO  - 10.1201/b16513-37
ER  - 

@conference{
author = "Buljak, Vladimir and Garbowski, Tomasz",
year = "2014",
abstract = "Model reduction techniques generate low-dimensional models to parametrize PDEs in order to allow for efficient evaluation of highly non-linear problems in many-query and real-time context. Computing time in these methods is divided into a time consuming "off-line" phase needed to "train" a surrogate model, which is further used in "on-line" phase providing accurate results in a much faster way. The accuracy of these methods is strictly connected to the number of points in which the system response is previously computed and on their distribution in a parameter space. For a given number of analysis decided to be "invested" for the design of surrogate model, the accuracy can be further improved by the adequate distribution of them in a parameter space. Two methods of robust samples distribution are proposed here. A first method is based on interactive nodes aimed to optimize the distribution of them. A second is based on an optimal Latin hypercube design. Both presented methods are flexible with respect to the number of nodes involved and they can provide uniform distribution for any arbitrary number of them. Furthermore, they allow also for taking into account different importance of divers parameters.",
publisher = "Taylor and Francis - Balkema",
journal = "Recent Advances in Computational Mechanics - Proceedings of the 20th International Conference on Com",
title = "Efficient methods for optimal space filling in model reduction techniques",
pages = "291-285",
doi = "10.1201/b16513-37"
}

Buljak, V.,& Garbowski, T.. (2014). Efficient methods for optimal space filling in model reduction techniques. in Recent Advances in Computational Mechanics - Proceedings of the 20th International Conference on Com
Taylor and Francis - Balkema., 285-291.
https://doi.org/10.1201/b16513-37

Buljak V, Garbowski T. Efficient methods for optimal space filling in model reduction techniques. in Recent Advances in Computational Mechanics - Proceedings of the 20th International Conference on Com. 2014;:285-291.
doi:10.1201/b16513-37 .

Buljak, Vladimir, Garbowski, Tomasz, "Efficient methods for optimal space filling in model reduction techniques" in Recent Advances in Computational Mechanics - Proceedings of the 20th International Conference on Com (2014):285-291,
https://doi.org/10.1201/b16513-37 . .

TY  - JOUR
AU  - Bocciarelli, M.
AU  - Buljak, Vladimir
AU  - Moy, C. K. S.
AU  - Ringer, S. P.
AU  - Ranzi, G.
PY  - 2014
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/1861
AB  - Indentation tests are frequently employed to determine the mechanical properties of materials and are particularly suitable when dealing with small components due to their "quasi-non-destructiveness". During an indentation test, the material is subjected to a triaxial stress state and, because of this, the mechanical properties cannot be inferred directly from the experiments. In these cases, suitable procedures must be implemented to derive them and, among the different alternatives available in the literature, the inverse analysis approach has been extensively studied and applied to a wide range of materials and systems. When the inverse analysis procedure relies on the use of a time-consuming finite element model for the modelling of an experimental test, the results are accurate yet computationally demanding. In the present paper, a numerically efficient approach was implemented, which relied on the use of an 'a priori' finite element model reduction procedure. This consists of a Proper Orthogonal Decomposition (POD) model that simulates the response of the material when subjected to an indentation test. The experimental data used in this study as input to the inverse analysis approach consist of both indentation curves and pile-up markings observed at the end of the indentation in the samples. Independent tensile tests were carried out on samples of aluminium alloys AA 6061-O and AA 7075-O. These experimental results were used for the validation of the proposed numerical approach. These results highlighted the accuracy and efficiency of the proposed procedure.
PB  - Elsevier, Amsterdam
T2  - Computational Materials Science
T1  - An inverse analysis approach based on a POD direct model for the mechanical characterization of metallic materials
EP  - 308
SP  - 302
VL  - 95
DO  - 10.1016/j.commatsci.2014.07.025
ER  - 

@article{
author = "Bocciarelli, M. and Buljak, Vladimir and Moy, C. K. S. and Ringer, S. P. and Ranzi, G.",
year = "2014",
abstract = "Indentation tests are frequently employed to determine the mechanical properties of materials and are particularly suitable when dealing with small components due to their "quasi-non-destructiveness". During an indentation test, the material is subjected to a triaxial stress state and, because of this, the mechanical properties cannot be inferred directly from the experiments. In these cases, suitable procedures must be implemented to derive them and, among the different alternatives available in the literature, the inverse analysis approach has been extensively studied and applied to a wide range of materials and systems. When the inverse analysis procedure relies on the use of a time-consuming finite element model for the modelling of an experimental test, the results are accurate yet computationally demanding. In the present paper, a numerically efficient approach was implemented, which relied on the use of an 'a priori' finite element model reduction procedure. This consists of a Proper Orthogonal Decomposition (POD) model that simulates the response of the material when subjected to an indentation test. The experimental data used in this study as input to the inverse analysis approach consist of both indentation curves and pile-up markings observed at the end of the indentation in the samples. Independent tensile tests were carried out on samples of aluminium alloys AA 6061-O and AA 7075-O. These experimental results were used for the validation of the proposed numerical approach. These results highlighted the accuracy and efficiency of the proposed procedure.",
publisher = "Elsevier, Amsterdam",
journal = "Computational Materials Science",
title = "An inverse analysis approach based on a POD direct model for the mechanical characterization of metallic materials",
pages = "308-302",
volume = "95",
doi = "10.1016/j.commatsci.2014.07.025"
}

Bocciarelli, M., Buljak, V., Moy, C. K. S., Ringer, S. P.,& Ranzi, G.. (2014). An inverse analysis approach based on a POD direct model for the mechanical characterization of metallic materials. in Computational Materials Science
Elsevier, Amsterdam., 95, 302-308.
https://doi.org/10.1016/j.commatsci.2014.07.025

Bocciarelli M, Buljak V, Moy CKS, Ringer SP, Ranzi G. An inverse analysis approach based on a POD direct model for the mechanical characterization of metallic materials. in Computational Materials Science. 2014;95:302-308.
doi:10.1016/j.commatsci.2014.07.025 .

Bocciarelli, M., Buljak, Vladimir, Moy, C. K. S., Ringer, S. P., Ranzi, G., "An inverse analysis approach based on a POD direct model for the mechanical characterization of metallic materials" in Computational Materials Science, 95 (2014):302-308,
https://doi.org/10.1016/j.commatsci.2014.07.025 . .

TY  - JOUR
AU  - Buljak, Vladimir
AU  - Bocciarelli, M.
AU  - Maier, Giulio
PY  - 2014
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2036
AB  - Anisotropy, usually orthotropy, arises in structural materials, particularly metals, due to production processes like laminations and concerns primarily parameters which govern the plastic behavior. Identification of such parameters is investigated here by a novel approach with the following features: experimental data provided by indentation curves only (not by imprint geometry); indenter shape with elliptical cross-section derived from classical conical or spherical shape and optimized by sensitivity analyses; indentation test repeated in near places after indenter rotation; deterministic inverse analyses centered on discrepancy function minimization and made computationally economical by an 'a priori' model reduction procedure.
PB  - Kluwer Academic Publishers
T2  - Meccanica
T1  - Mechanical characterization of anisotropic elasto-plastic materials by indentation curves only
EP  - 1599
IS  - 7
SP  - 1587
VL  - 49
DO  - 10.1007/s11012-014-9940-y
ER  - 

@article{
author = "Buljak, Vladimir and Bocciarelli, M. and Maier, Giulio",
year = "2014",
abstract = "Anisotropy, usually orthotropy, arises in structural materials, particularly metals, due to production processes like laminations and concerns primarily parameters which govern the plastic behavior. Identification of such parameters is investigated here by a novel approach with the following features: experimental data provided by indentation curves only (not by imprint geometry); indenter shape with elliptical cross-section derived from classical conical or spherical shape and optimized by sensitivity analyses; indentation test repeated in near places after indenter rotation; deterministic inverse analyses centered on discrepancy function minimization and made computationally economical by an 'a priori' model reduction procedure.",
publisher = "Kluwer Academic Publishers",
journal = "Meccanica",
title = "Mechanical characterization of anisotropic elasto-plastic materials by indentation curves only",
pages = "1599-1587",
number = "7",
volume = "49",
doi = "10.1007/s11012-014-9940-y"
}

Buljak, V., Bocciarelli, M.,& Maier, G.. (2014). Mechanical characterization of anisotropic elasto-plastic materials by indentation curves only. in Meccanica
Kluwer Academic Publishers., 49(7), 1587-1599.
https://doi.org/10.1007/s11012-014-9940-y

Buljak V, Bocciarelli M, Maier G. Mechanical characterization of anisotropic elasto-plastic materials by indentation curves only. in Meccanica. 2014;49(7):1587-1599.
doi:10.1007/s11012-014-9940-y .

Buljak, Vladimir, Bocciarelli, M., Maier, Giulio, "Mechanical characterization of anisotropic elasto-plastic materials by indentation curves only" in Meccanica, 49, no. 7 (2014):1587-1599,
https://doi.org/10.1007/s11012-014-9940-y . .

TY  - JOUR
AU  - Maier, Giulio
AU  - Buljak, Vladimir
AU  - Garbowski, Tomasz
AU  - Cocchetti, Giuseppe
AU  - Novati, Giorgio
PY  - 2014
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/1887
AB  - A survey is presented herein of some recent research contributions to the methodology of inverse structural analysis based on statical tests for diagnosis of possibly damaged structures and for mechanical characterization of materials in diverse industrial environments. The following issues are briefly considered: identifications of parameters in material models and of residual stresses on the basis of indentation experiments; mechanical characterization of free-foils and laminates by cruciform and compression tests and digital image correlation measurements; diagnosis, both superficially and in depth, of concrete dams, possibly affected by alkali-silica-reaction or otherwise damaged.
PB  - World Scientific Publ Co Pte Ltd, Singapore
T2  - International Journal of Computational Methods
T1  - Mechanical characterization of materials and diagnosis of structures by inverse analyses: some innovative procedures and applications
IS  - 3
VL  - 11
DO  - 10.1142/S0219876213430020
ER  - 

@article{
author = "Maier, Giulio and Buljak, Vladimir and Garbowski, Tomasz and Cocchetti, Giuseppe and Novati, Giorgio",
year = "2014",
abstract = "A survey is presented herein of some recent research contributions to the methodology of inverse structural analysis based on statical tests for diagnosis of possibly damaged structures and for mechanical characterization of materials in diverse industrial environments. The following issues are briefly considered: identifications of parameters in material models and of residual stresses on the basis of indentation experiments; mechanical characterization of free-foils and laminates by cruciform and compression tests and digital image correlation measurements; diagnosis, both superficially and in depth, of concrete dams, possibly affected by alkali-silica-reaction or otherwise damaged.",
publisher = "World Scientific Publ Co Pte Ltd, Singapore",
journal = "International Journal of Computational Methods",
title = "Mechanical characterization of materials and diagnosis of structures by inverse analyses: some innovative procedures and applications",
number = "3",
volume = "11",
doi = "10.1142/S0219876213430020"
}

Maier, G., Buljak, V., Garbowski, T., Cocchetti, G.,& Novati, G.. (2014). Mechanical characterization of materials and diagnosis of structures by inverse analyses: some innovative procedures and applications. in International Journal of Computational Methods
World Scientific Publ Co Pte Ltd, Singapore., 11(3).
https://doi.org/10.1142/S0219876213430020

Maier G, Buljak V, Garbowski T, Cocchetti G, Novati G. Mechanical characterization of materials and diagnosis of structures by inverse analyses: some innovative procedures and applications. in International Journal of Computational Methods. 2014;11(3).
doi:10.1142/S0219876213430020 .

Maier, Giulio, Buljak, Vladimir, Garbowski, Tomasz, Cocchetti, Giuseppe, Novati, Giorgio, "Mechanical characterization of materials and diagnosis of structures by inverse analyses: some innovative procedures and applications" in International Journal of Computational Methods, 11, no. 3 (2014),
https://doi.org/10.1142/S0219876213430020 . .

TY  - JOUR
AU  - Buljak, Vladimir
AU  - Cocchetti, Giuseppe
AU  - Maier, Giulio
PY  - 2013
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/1709
AB  - In several engineering areas structural analyses concern also fracture processes of brittle materials and employ cohesive crack models. Calibrations of such models, i.e. identification of their parameters by tests, computer simulations of the tests and inverse analyses, have been investigated in the literature particularly with reference to non-destructive indentation tests at various scales.To this timely research, the following contributions are presented in this paper: a simple piecewise-linear cohesive crack model is considered for brittle materials (here glass, for example); for its calibration by "non-destructive" indentation tests novel shapes are attributed to instrumented indenters, in order to make fracture the dominant feature of the specimen response to the test; such shapes are comparatively examined and optimized by sensitivity analyses; a procedure for inverse analysis is developed and computationally tested, based on penetration versus increasing force only (no imprint measurements by profilometers) and is made "economical" (i.e. computationally fast, "in situ" by small computers) by model reduction through proper orthogonal decomposition in view of repeated industrial applications.
PB  - Springer, Dordrecht
T2  - International Journal of Fracture
T1  - Calibration of brittle fracture models by sharp indenters and inverse analysis
EP  - 136
IS  - 1-2
SP  - 123
VL  - 184
DO  - 10.1007/s10704-013-9841-4
ER  - 

@article{
author = "Buljak, Vladimir and Cocchetti, Giuseppe and Maier, Giulio",
year = "2013",
abstract = "In several engineering areas structural analyses concern also fracture processes of brittle materials and employ cohesive crack models. Calibrations of such models, i.e. identification of their parameters by tests, computer simulations of the tests and inverse analyses, have been investigated in the literature particularly with reference to non-destructive indentation tests at various scales.To this timely research, the following contributions are presented in this paper: a simple piecewise-linear cohesive crack model is considered for brittle materials (here glass, for example); for its calibration by "non-destructive" indentation tests novel shapes are attributed to instrumented indenters, in order to make fracture the dominant feature of the specimen response to the test; such shapes are comparatively examined and optimized by sensitivity analyses; a procedure for inverse analysis is developed and computationally tested, based on penetration versus increasing force only (no imprint measurements by profilometers) and is made "economical" (i.e. computationally fast, "in situ" by small computers) by model reduction through proper orthogonal decomposition in view of repeated industrial applications.",
publisher = "Springer, Dordrecht",
journal = "International Journal of Fracture",
title = "Calibration of brittle fracture models by sharp indenters and inverse analysis",
pages = "136-123",
number = "1-2",
volume = "184",
doi = "10.1007/s10704-013-9841-4"
}

Buljak, V., Cocchetti, G.,& Maier, G.. (2013). Calibration of brittle fracture models by sharp indenters and inverse analysis. in International Journal of Fracture
Springer, Dordrecht., 184(1-2), 123-136.
https://doi.org/10.1007/s10704-013-9841-4

Buljak V, Cocchetti G, Maier G. Calibration of brittle fracture models by sharp indenters and inverse analysis. in International Journal of Fracture. 2013;184(1-2):123-136.
doi:10.1007/s10704-013-9841-4 .

Buljak, Vladimir, Cocchetti, Giuseppe, Maier, Giulio, "Calibration of brittle fracture models by sharp indenters and inverse analysis" in International Journal of Fracture, 184, no. 1-2 (2013):123-136,
https://doi.org/10.1007/s10704-013-9841-4 . .

TY  - JOUR
AU  - Bolzon, Gabriella
AU  - Buljak, Vladimir
AU  - Zappa, E.
PY  - 2012
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/1543
AB  - The fracture properties of thin aluminum inclusions embedded in anisotropic paperboard composites, of interest for food and beverage packaging industry, can be determined by performing tensile tests on non-conventional heterogeneous specimens. The region of interest of the investigated material samples is monitored all along the experiment by digital image correlation techniques, which allow to recover qualitative and quantitative information about the metal deformation and about the evolution of the damaging processes leading to the detachment of the inclusion from the surrounding laminate composite. The interpretation of the laboratory results is supported by the numerical simulation of the tests.
PB  - Gruppo Italiano Frattura
T2  - Frattura ed Integrita Strutturale
T1  - Characterization of fracture properties of thin aluminum inclusions embedded in anisotropic laminate composites
EP  - 28
SP  - 20
VL  - 19
DO  - 10.3221/IGF-ESIS.19.02
ER  - 

@article{
author = "Bolzon, Gabriella and Buljak, Vladimir and Zappa, E.",
year = "2012",
abstract = "The fracture properties of thin aluminum inclusions embedded in anisotropic paperboard composites, of interest for food and beverage packaging industry, can be determined by performing tensile tests on non-conventional heterogeneous specimens. The region of interest of the investigated material samples is monitored all along the experiment by digital image correlation techniques, which allow to recover qualitative and quantitative information about the metal deformation and about the evolution of the damaging processes leading to the detachment of the inclusion from the surrounding laminate composite. The interpretation of the laboratory results is supported by the numerical simulation of the tests.",
publisher = "Gruppo Italiano Frattura",
journal = "Frattura ed Integrita Strutturale",
title = "Characterization of fracture properties of thin aluminum inclusions embedded in anisotropic laminate composites",
pages = "28-20",
volume = "19",
doi = "10.3221/IGF-ESIS.19.02"
}

Bolzon, G., Buljak, V.,& Zappa, E.. (2012). Characterization of fracture properties of thin aluminum inclusions embedded in anisotropic laminate composites. in Frattura ed Integrita Strutturale
Gruppo Italiano Frattura., 19, 20-28.
https://doi.org/10.3221/IGF-ESIS.19.02

Bolzon G, Buljak V, Zappa E. Characterization of fracture properties of thin aluminum inclusions embedded in anisotropic laminate composites. in Frattura ed Integrita Strutturale. 2012;19:20-28.
doi:10.3221/IGF-ESIS.19.02 .

Bolzon, Gabriella, Buljak, Vladimir, Zappa, E., "Characterization of fracture properties of thin aluminum inclusions embedded in anisotropic laminate composites" in Frattura ed Integrita Strutturale, 19 (2012):20-28,
https://doi.org/10.3221/IGF-ESIS.19.02 . .

TY  - JOUR
AU  - Buljak, Vladimir
AU  - Maier, Giulio
PY  - 2012
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/1518
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Mechanics Research Communications
T1  - Identification of residual stresses by instrumented elliptical indentation and inverse analysis (vol 41, pg 21, 2012)
EP  - 90
SP  - 90
VL  - 46
DO  - 10.1016/j.mechrescom.2012.07.005
ER  - 

@article{
author = "Buljak, Vladimir and Maier, Giulio",
year = "2012",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Mechanics Research Communications",
title = "Identification of residual stresses by instrumented elliptical indentation and inverse analysis (vol 41, pg 21, 2012)",
pages = "90-90",
volume = "46",
doi = "10.1016/j.mechrescom.2012.07.005"
}

Buljak, V.,& Maier, G.. (2012). Identification of residual stresses by instrumented elliptical indentation and inverse analysis (vol 41, pg 21, 2012). in Mechanics Research Communications
Pergamon-Elsevier Science Ltd, Oxford., 46, 90-90.
https://doi.org/10.1016/j.mechrescom.2012.07.005

Buljak V, Maier G. Identification of residual stresses by instrumented elliptical indentation and inverse analysis (vol 41, pg 21, 2012). in Mechanics Research Communications. 2012;46:90-90.
doi:10.1016/j.mechrescom.2012.07.005 .

Buljak, Vladimir, Maier, Giulio, "Identification of residual stresses by instrumented elliptical indentation and inverse analysis (vol 41, pg 21, 2012)" in Mechanics Research Communications, 46 (2012):90-90,
https://doi.org/10.1016/j.mechrescom.2012.07.005 . .

TY  - JOUR
AU  - Buljak, Vladimir
AU  - Maier, Giulio
PY  - 2012
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/1449
AB  - The residual stress tensor near the surface of a metal structural component or products of metallurgical processes (particularly welding) is considered in view of the estimation of its governing components. These are: the two principal stresses if the directions are "a priori" known as assumed here for the preliminary optimization of the indenter shape; otherwise two normal stresses and a shear stress according to a preselected reference system. In both situations the material is assumed to be endowed with known elastic-plastic properties. The novel parameter identification procedure investigated herein can be outlined as follows, when the unknown stresses are three: an instrumented indenter is adopted with elliptical section across the axis of an originally conical, or, as an alternative, of an originally spherical shape; three indentations are performed with the ellipse axis rotated by 45 in a sequence, in three locations near to each other at minimal distances apt to avoid interference; the three digitalized indentation curves (loading-unloading force versus penetration) are the source of the experimental data set used as input of inverse analysis; this is carried out by a fast method consisting of finite element simulations of the tests, "proper orthogonal decomposition", "radial basis function" interpolation, and a first-order algorithm for the minimization of the discrepancy function. When the unknowns are the two principal stresses (directions known) two orthogonal indentations turn out to be sufficient.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Mechanics Research Communications
T1  - Identification of residual stresses by instrumented elliptical indentation and inverse analysis
EP  - 29
SP  - 21
VL  - 41
DO  - 10.1016/j.mechrescom.2012.02.002
ER  - 

@article{
author = "Buljak, Vladimir and Maier, Giulio",
year = "2012",
abstract = "The residual stress tensor near the surface of a metal structural component or products of metallurgical processes (particularly welding) is considered in view of the estimation of its governing components. These are: the two principal stresses if the directions are "a priori" known as assumed here for the preliminary optimization of the indenter shape; otherwise two normal stresses and a shear stress according to a preselected reference system. In both situations the material is assumed to be endowed with known elastic-plastic properties. The novel parameter identification procedure investigated herein can be outlined as follows, when the unknown stresses are three: an instrumented indenter is adopted with elliptical section across the axis of an originally conical, or, as an alternative, of an originally spherical shape; three indentations are performed with the ellipse axis rotated by 45 in a sequence, in three locations near to each other at minimal distances apt to avoid interference; the three digitalized indentation curves (loading-unloading force versus penetration) are the source of the experimental data set used as input of inverse analysis; this is carried out by a fast method consisting of finite element simulations of the tests, "proper orthogonal decomposition", "radial basis function" interpolation, and a first-order algorithm for the minimization of the discrepancy function. When the unknowns are the two principal stresses (directions known) two orthogonal indentations turn out to be sufficient.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Mechanics Research Communications",
title = "Identification of residual stresses by instrumented elliptical indentation and inverse analysis",
pages = "29-21",
volume = "41",
doi = "10.1016/j.mechrescom.2012.02.002"
}

Buljak, V.,& Maier, G.. (2012). Identification of residual stresses by instrumented elliptical indentation and inverse analysis. in Mechanics Research Communications
Pergamon-Elsevier Science Ltd, Oxford., 41, 21-29.
https://doi.org/10.1016/j.mechrescom.2012.02.002

Buljak V, Maier G. Identification of residual stresses by instrumented elliptical indentation and inverse analysis. in Mechanics Research Communications. 2012;41:21-29.
doi:10.1016/j.mechrescom.2012.02.002 .

Buljak, Vladimir, Maier, Giulio, "Identification of residual stresses by instrumented elliptical indentation and inverse analysis" in Mechanics Research Communications, 41 (2012):21-29,
https://doi.org/10.1016/j.mechrescom.2012.02.002 . .

TY  - JOUR
AU  - Bolzon, Gabriella
AU  - Buljak, Vladimir
PY  - 2011
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/1204
AB  - Parametric studies and identification problems require to perform repeated analyses, where only a few input parameters are varied among those defining the problem of interest, often associated to complex numerical simulations. In fact, physical phenomena relevant to several practical applications involve coupled material and geometry non-linearities. In these situations, accurate but expensive computations, usually carried out by the finite element method, may be replaced by numerical procedures based on proper orthogonal decomposition combined with radial basis function interpolation. Besides drastically reducing computing times and costs, this approach is capable of retaining the essential features of the considered system responses while filtering most disturbances. These features are illustrated in this paper with specific reference to some elastic-plastic problems. The presented results can however be easily extended to other meaningful engineering situations.
PB  - Springer, New York
T2  - Computational Mechanics
T1  - An effective computational tool for parametric studies and identification problems in materials mechanics
EP  - 687
IS  - 6
SP  - 675
VL  - 48
DO  - 10.1007/s00466-011-0611-8
ER  - 

@article{
author = "Bolzon, Gabriella and Buljak, Vladimir",
year = "2011",
abstract = "Parametric studies and identification problems require to perform repeated analyses, where only a few input parameters are varied among those defining the problem of interest, often associated to complex numerical simulations. In fact, physical phenomena relevant to several practical applications involve coupled material and geometry non-linearities. In these situations, accurate but expensive computations, usually carried out by the finite element method, may be replaced by numerical procedures based on proper orthogonal decomposition combined with radial basis function interpolation. Besides drastically reducing computing times and costs, this approach is capable of retaining the essential features of the considered system responses while filtering most disturbances. These features are illustrated in this paper with specific reference to some elastic-plastic problems. The presented results can however be easily extended to other meaningful engineering situations.",
publisher = "Springer, New York",
journal = "Computational Mechanics",
title = "An effective computational tool for parametric studies and identification problems in materials mechanics",
pages = "687-675",
number = "6",
volume = "48",
doi = "10.1007/s00466-011-0611-8"
}

Bolzon, G.,& Buljak, V.. (2011). An effective computational tool for parametric studies and identification problems in materials mechanics. in Computational Mechanics
Springer, New York., 48(6), 675-687.
https://doi.org/10.1007/s00466-011-0611-8

Bolzon G, Buljak V. An effective computational tool for parametric studies and identification problems in materials mechanics. in Computational Mechanics. 2011;48(6):675-687.
doi:10.1007/s00466-011-0611-8 .

Bolzon, Gabriella, Buljak, Vladimir, "An effective computational tool for parametric studies and identification problems in materials mechanics" in Computational Mechanics, 48, no. 6 (2011):675-687,
https://doi.org/10.1007/s00466-011-0611-8 . .