TY  - JOUR
AU  - Raković, Dragan
AU  - Simonović, Aleksandar
AU  - Grbović, Aleksandar
AU  - Radović, Ljubica
AU  - Vorkapić, Miloš
AU  - Krstić, Branimir
PY  - 2021
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/3490
AB  - This paper presents the failure analysis results of the helicopter skid landing gear. The helicopter skid landing gear fractured while the helicopter was on the ground at the airport. The aft cross tube of the landing gear assembly was found fractured into two pieces. Observation of crack propagation area at low magnification revealed numerous secondary cracks, inner surface irregularities while fracture surface indicated fatigue process. Macro-fractographic analysis of the fracture surface disclosed features that gave additional indication of fatigue. Examination of mating fracture surfaces under scanning electron microscope (SEM) detected the existence of irregularities in the material. Chemical analysis showed the aft cross tube is made of high-strength aluminum alloy. The stress analysis of skid landing gear, using the finite element method (FEM), has identified the stress-deformation condition of the helicopter landing gear with a detail insight of the stress state in the vicinity of the crack origin. The stress value, in case of maximal takeoff weight, was very high in the crack initiation zone. The results indicate the superposition of manufacturing-in, designing-in as well as operating in defects which led to total failure of the helicopter skid landing gear aft cross tube.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Engineering Failure Analysis
T1  - Fatigue fracture analysis of helicopter landing gear cross tube
VL  - 129
DO  - 10.1016/j.engfailanal.2021.105672
ER  - 

@article{
author = "Raković, Dragan and Simonović, Aleksandar and Grbović, Aleksandar and Radović, Ljubica and Vorkapić, Miloš and Krstić, Branimir",
year = "2021",
abstract = "This paper presents the failure analysis results of the helicopter skid landing gear. The helicopter skid landing gear fractured while the helicopter was on the ground at the airport. The aft cross tube of the landing gear assembly was found fractured into two pieces. Observation of crack propagation area at low magnification revealed numerous secondary cracks, inner surface irregularities while fracture surface indicated fatigue process. Macro-fractographic analysis of the fracture surface disclosed features that gave additional indication of fatigue. Examination of mating fracture surfaces under scanning electron microscope (SEM) detected the existence of irregularities in the material. Chemical analysis showed the aft cross tube is made of high-strength aluminum alloy. The stress analysis of skid landing gear, using the finite element method (FEM), has identified the stress-deformation condition of the helicopter landing gear with a detail insight of the stress state in the vicinity of the crack origin. The stress value, in case of maximal takeoff weight, was very high in the crack initiation zone. The results indicate the superposition of manufacturing-in, designing-in as well as operating in defects which led to total failure of the helicopter skid landing gear aft cross tube.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Engineering Failure Analysis",
title = "Fatigue fracture analysis of helicopter landing gear cross tube",
volume = "129",
doi = "10.1016/j.engfailanal.2021.105672"
}

Raković, D., Simonović, A., Grbović, A., Radović, L., Vorkapić, M.,& Krstić, B.. (2021). Fatigue fracture analysis of helicopter landing gear cross tube. in Engineering Failure Analysis
Pergamon-Elsevier Science Ltd, Oxford., 129.
https://doi.org/10.1016/j.engfailanal.2021.105672

Raković D, Simonović A, Grbović A, Radović L, Vorkapić M, Krstić B. Fatigue fracture analysis of helicopter landing gear cross tube. in Engineering Failure Analysis. 2021;129.
doi:10.1016/j.engfailanal.2021.105672 .

Raković, Dragan, Simonović, Aleksandar, Grbović, Aleksandar, Radović, Ljubica, Vorkapić, Miloš, Krstić, Branimir, "Fatigue fracture analysis of helicopter landing gear cross tube" in Engineering Failure Analysis, 129 (2021),
https://doi.org/10.1016/j.engfailanal.2021.105672 . .

TY  - JOUR
AU  - Rebhi, Lamine
AU  - Dinulović, Mirko
AU  - Dunjić, Momčilo
AU  - Grbović, Aleksandar
AU  - Krstić, Branimir
PY  - 2017
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2615
AB  - U radu je predstavljena metoda proračuna efektivnog modula smicanja kompozitnih panela sa sendvič ispunom. Ovaj koeficijent elastičnosti predstavlja vrlo važnu karakteristiku materijala, posebno kod konstrukcija koje su izložene čistoj torziji ili kombinaciji savijanja i torzije. Strukture koje su ispitivane u ovom istraživanju su ravne ploče načinjene od gornjeg i donjeg kompozitnog lica i ispunom (jezgrom) od šestougaonog kompozitnog sendvič materijala. Polazeći od klasične teorije laminata određen je efektivni modul smicanja gornje i donje ploče za svaki sloj u stoku (laminatu). Ovi slojevi platana se svode u jedan kompozitni sloj sa različitim orijentacijama vlakana i debljine. Da bi se verifikovao ovaj prilaz korišćen je Metod konačnih elemenata da bi se odredila pomeranja, deformacije i naponi u kompozitnim pločama i sendvič ispuni. Dva tipa numeričkih modela su upoređivani: početni model, gde su svi spojevi ploče modelirani sa svojim karakteristikama i drugi model kod kojeg su spojeni u jednu celinu sa svojim ekvivalentnim karakteristikama.
AB  - Calculation Method for the effective shear modulus of composite plates with sandwich cores is presented. This elastic coefficient represents one very important material property especially in constructions subjected to pure torsion and combined bending - torsion. The structures investigated in this research are flat plates made of top and bottom composite facesheets and hexagonal composite material sandwich core. Starting from classical Lamination theory the effective shear modulus of top and bottom plates was determined for each ply in the stack up sequence. These plies were 'lumped into a single composite layer for different fiber orientations and plies thicknesses. To verify this approach Finite element method was used to determine the displacement, stress and strain field on Composite plates with Sandwich Cores. Two types of models were compared: The initial model where all the material components, plates and the core were modeled with their intrinsic properties and 'lumped' model with calculated effective elastic coefficients.
PB  - Univerzitet u Beogradu - Mašinski fakultet, Beograd
T2  - FME Transactions
T1  - Proračun efektivnog modula smicanja kompozitnih sendvič panela
T1  - Calculation of the effective shear modulus of composite sandwich panels
EP  - 542
IS  - 4
SP  - 537
VL  - 45
DO  - 10.5937/fmet1704537R
ER  - 

@article{
author = "Rebhi, Lamine and Dinulović, Mirko and Dunjić, Momčilo and Grbović, Aleksandar and Krstić, Branimir",
year = "2017",
abstract = "U radu je predstavljena metoda proračuna efektivnog modula smicanja kompozitnih panela sa sendvič ispunom. Ovaj koeficijent elastičnosti predstavlja vrlo važnu karakteristiku materijala, posebno kod konstrukcija koje su izložene čistoj torziji ili kombinaciji savijanja i torzije. Strukture koje su ispitivane u ovom istraživanju su ravne ploče načinjene od gornjeg i donjeg kompozitnog lica i ispunom (jezgrom) od šestougaonog kompozitnog sendvič materijala. Polazeći od klasične teorije laminata određen je efektivni modul smicanja gornje i donje ploče za svaki sloj u stoku (laminatu). Ovi slojevi platana se svode u jedan kompozitni sloj sa različitim orijentacijama vlakana i debljine. Da bi se verifikovao ovaj prilaz korišćen je Metod konačnih elemenata da bi se odredila pomeranja, deformacije i naponi u kompozitnim pločama i sendvič ispuni. Dva tipa numeričkih modela su upoređivani: početni model, gde su svi spojevi ploče modelirani sa svojim karakteristikama i drugi model kod kojeg su spojeni u jednu celinu sa svojim ekvivalentnim karakteristikama., Calculation Method for the effective shear modulus of composite plates with sandwich cores is presented. This elastic coefficient represents one very important material property especially in constructions subjected to pure torsion and combined bending - torsion. The structures investigated in this research are flat plates made of top and bottom composite facesheets and hexagonal composite material sandwich core. Starting from classical Lamination theory the effective shear modulus of top and bottom plates was determined for each ply in the stack up sequence. These plies were 'lumped into a single composite layer for different fiber orientations and plies thicknesses. To verify this approach Finite element method was used to determine the displacement, stress and strain field on Composite plates with Sandwich Cores. Two types of models were compared: The initial model where all the material components, plates and the core were modeled with their intrinsic properties and 'lumped' model with calculated effective elastic coefficients.",
publisher = "Univerzitet u Beogradu - Mašinski fakultet, Beograd",
journal = "FME Transactions",
title = "Proračun efektivnog modula smicanja kompozitnih sendvič panela, Calculation of the effective shear modulus of composite sandwich panels",
pages = "542-537",
number = "4",
volume = "45",
doi = "10.5937/fmet1704537R"
}

Rebhi, L., Dinulović, M., Dunjić, M., Grbović, A.,& Krstić, B.. (2017). Proračun efektivnog modula smicanja kompozitnih sendvič panela. in FME Transactions
Univerzitet u Beogradu - Mašinski fakultet, Beograd., 45(4), 537-542.
https://doi.org/10.5937/fmet1704537R

Rebhi L, Dinulović M, Dunjić M, Grbović A, Krstić B. Proračun efektivnog modula smicanja kompozitnih sendvič panela. in FME Transactions. 2017;45(4):537-542.
doi:10.5937/fmet1704537R .

Rebhi, Lamine, Dinulović, Mirko, Dunjić, Momčilo, Grbović, Aleksandar, Krstić, Branimir, "Proračun efektivnog modula smicanja kompozitnih sendvič panela" in FME Transactions, 45, no. 4 (2017):537-542,
https://doi.org/10.5937/fmet1704537R . .

TY  - JOUR
AU  - Rebhi, Lamine
AU  - Dinulović, Mirko
AU  - Andrić, Predrag
AU  - Dodić, Marjan
AU  - Krstić, Branimir
PY  - 2016
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2280
AB  - U radu je određen efektivni modul klizanja kompozitnog panela sa saćastom ispunom. Ovaj elastični koeficijent predstavlja veoma važnu karakteristiku kompozitnih panela, naročito kod kompozitnih konstrukcija koje su izložene uvijanju kao i kombinovanom uvijanju sa savijanjem. Analizirane strukture u ovom radu sastoje se od gornje i donje kompozitne ploče (različitih tipova karbonskih vlakana, T300, AS4 u epoksidnoj matrici) kao i saćaste ispune (HexWeb EC engineered core). Polazeći od klasične teorije lamine, efektivni modul elastičnosti klizanja je određen za svaki sloj u kompozitnoj ploči. Ovi slojevi su spojeni u jedinstveni kompozitni sloj za različita usmerenja vlakana kao i debljine lamina. Elastični koeficijenti saćaste ispune HexWeb središnjeg sloja kompozitnog panela su izračunati koristeći teoriju Master Evans u cilju dobijanja ekvivalentnih vrednosti. Za proveru predloženog pristupa korišćen je metod konačnih elemenata, u cilju dobijanja polja pomeranja, deformacija i napona u kompozitnim pločama i saćastoj ispuni. Dva tipa numeričkih modela su upoređena: početni model, pri čemu su svi slojevi ploče modelirani sa svojim karakteristikama i drugi model kod kojeg su spojeni u jednu celinu sa svojim ekvivalentnim karakteristikama. Zaključeno je da se ekvivalentni metod određivanja modula klizanja kompozitnih panela sa saćastim ispunama može efikasno primeniti u slučajevima kada su gornja i donja kompozitna ploča simetričnog slaganja ili uopšte kvaziizotropna.
AB  - In the presented paper the effective shear modulus of composite plates with honeycomb core is determined. This elastic coefficient represents one very important property, especially in constructions subjected to torsion and combined bending - torsion. The structures investigated in this research consisted of top and bottom plates (of different types of carbon fibers, T300, AS4 in epoxy matrix) and honeycomb core (HexWeb engineered core). Starting from classical lamination theory, the effective shear modulus of top and bottom plates was determined for each ply in the stack up sequence. These plies were 'lumped' into a single composite layer for different fiber orientations and plies thicknesses. Elastic coefficients for the HexWeb engineered core were obtained using Master and Evans relations for the equivalent properties of honeycomb cores. To verify this approach, finite element method was used to determine the displacement, stress and strain field on composite plates with honeycomb core. Two types of models were compared: the initial model where all the material components, plates and the core were modeled with their intrinsic properties and 'lumped' model with calculated effective elastic coefficients. It was found that the method of effective shear modulus calculation can successfully be used in situations where top and bottom plates are symmetric or quasi isotropic in general.
PB  - Vojnotehnički institut, Beograd
T2  - Scientific Technical Review
T1  - Efektivni modul klizanja kompozitnih panela sa saćastim ispunom
T1  - Ëffektivnyj modul' sdviga kompozitnyh sëndvič-panelej so sotovoj strukturoj / (francuski) Module de cisaillement effectif des panneaux composites en nid d'abeilles
T1  - On the effective shear modulus of composite honeycomb sandwich panels
EP  - 65
IS  - 4
SP  - 59
VL  - 66
DO  - 10.5937/STR1604059R
ER  - 

@article{
author = "Rebhi, Lamine and Dinulović, Mirko and Andrić, Predrag and Dodić, Marjan and Krstić, Branimir",
year = "2016",
abstract = "U radu je određen efektivni modul klizanja kompozitnog panela sa saćastom ispunom. Ovaj elastični koeficijent predstavlja veoma važnu karakteristiku kompozitnih panela, naročito kod kompozitnih konstrukcija koje su izložene uvijanju kao i kombinovanom uvijanju sa savijanjem. Analizirane strukture u ovom radu sastoje se od gornje i donje kompozitne ploče (različitih tipova karbonskih vlakana, T300, AS4 u epoksidnoj matrici) kao i saćaste ispune (HexWeb EC engineered core). Polazeći od klasične teorije lamine, efektivni modul elastičnosti klizanja je određen za svaki sloj u kompozitnoj ploči. Ovi slojevi su spojeni u jedinstveni kompozitni sloj za različita usmerenja vlakana kao i debljine lamina. Elastični koeficijenti saćaste ispune HexWeb središnjeg sloja kompozitnog panela su izračunati koristeći teoriju Master Evans u cilju dobijanja ekvivalentnih vrednosti. Za proveru predloženog pristupa korišćen je metod konačnih elemenata, u cilju dobijanja polja pomeranja, deformacija i napona u kompozitnim pločama i saćastoj ispuni. Dva tipa numeričkih modela su upoređena: početni model, pri čemu su svi slojevi ploče modelirani sa svojim karakteristikama i drugi model kod kojeg su spojeni u jednu celinu sa svojim ekvivalentnim karakteristikama. Zaključeno je da se ekvivalentni metod određivanja modula klizanja kompozitnih panela sa saćastim ispunama može efikasno primeniti u slučajevima kada su gornja i donja kompozitna ploča simetričnog slaganja ili uopšte kvaziizotropna., In the presented paper the effective shear modulus of composite plates with honeycomb core is determined. This elastic coefficient represents one very important property, especially in constructions subjected to torsion and combined bending - torsion. The structures investigated in this research consisted of top and bottom plates (of different types of carbon fibers, T300, AS4 in epoxy matrix) and honeycomb core (HexWeb engineered core). Starting from classical lamination theory, the effective shear modulus of top and bottom plates was determined for each ply in the stack up sequence. These plies were 'lumped' into a single composite layer for different fiber orientations and plies thicknesses. Elastic coefficients for the HexWeb engineered core were obtained using Master and Evans relations for the equivalent properties of honeycomb cores. To verify this approach, finite element method was used to determine the displacement, stress and strain field on composite plates with honeycomb core. Two types of models were compared: the initial model where all the material components, plates and the core were modeled with their intrinsic properties and 'lumped' model with calculated effective elastic coefficients. It was found that the method of effective shear modulus calculation can successfully be used in situations where top and bottom plates are symmetric or quasi isotropic in general.",
publisher = "Vojnotehnički institut, Beograd",
journal = "Scientific Technical Review",
title = "Efektivni modul klizanja kompozitnih panela sa saćastim ispunom, Ëffektivnyj modul' sdviga kompozitnyh sëndvič-panelej so sotovoj strukturoj / (francuski) Module de cisaillement effectif des panneaux composites en nid d'abeilles, On the effective shear modulus of composite honeycomb sandwich panels",
pages = "65-59",
number = "4",
volume = "66",
doi = "10.5937/STR1604059R"
}

Rebhi, L., Dinulović, M., Andrić, P., Dodić, M.,& Krstić, B.. (2016). Efektivni modul klizanja kompozitnih panela sa saćastim ispunom. in Scientific Technical Review
Vojnotehnički institut, Beograd., 66(4), 59-65.
https://doi.org/10.5937/STR1604059R

Rebhi L, Dinulović M, Andrić P, Dodić M, Krstić B. Efektivni modul klizanja kompozitnih panela sa saćastim ispunom. in Scientific Technical Review. 2016;66(4):59-65.
doi:10.5937/STR1604059R .

Rebhi, Lamine, Dinulović, Mirko, Andrić, Predrag, Dodić, Marjan, Krstić, Branimir, "Efektivni modul klizanja kompozitnih panela sa saćastim ispunom" in Scientific Technical Review, 66, no. 4 (2016):59-65,
https://doi.org/10.5937/STR1604059R . .

TY  - JOUR
AU  - Krstić, Branimir
AU  - Rebhi, Lamine
AU  - Ilić, Nada
AU  - Dodić, Marjan
AU  - Dinulović, Mirko
AU  - Andrić, Predrag
AU  - Trifković, Dragan
PY  - 2016
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2451
AB  - The mounting bolt of helicopter main gearbox support strut was fractured into two pieces during the flight mission. The fracture occurred at the root of the first engaged thread of the bolt-nut assembly. Visual inspection of the fracture zone revealed cracks, formed by interlinking of corrosion pits, at the almost all thread roots of the bolt. Energy dispersive spectroscopy disclosed significant damage of the cadmium plating as well as the presence of large amounts of corrosion products at the bolt threads. Through the fractography and metallography analysis, it was found that the mounting bolt failed due to hydrogen-induced intergranular stress corrosion cracking (HI-IGSCC). The finite element (FE) analysis confirmed that the crack origin was located at the area with the maximum tensile stress in the bolt.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Engineering Failure Analysis
T1  - Failure of mounting bolt of helicopter main gearbox support strut
EP  - 363
SP  - 351
VL  - 70
DO  - 10.1016/j.engfailanal.2016.09.012
ER  - 

@article{
author = "Krstić, Branimir and Rebhi, Lamine and Ilić, Nada and Dodić, Marjan and Dinulović, Mirko and Andrić, Predrag and Trifković, Dragan",
year = "2016",
abstract = "The mounting bolt of helicopter main gearbox support strut was fractured into two pieces during the flight mission. The fracture occurred at the root of the first engaged thread of the bolt-nut assembly. Visual inspection of the fracture zone revealed cracks, formed by interlinking of corrosion pits, at the almost all thread roots of the bolt. Energy dispersive spectroscopy disclosed significant damage of the cadmium plating as well as the presence of large amounts of corrosion products at the bolt threads. Through the fractography and metallography analysis, it was found that the mounting bolt failed due to hydrogen-induced intergranular stress corrosion cracking (HI-IGSCC). The finite element (FE) analysis confirmed that the crack origin was located at the area with the maximum tensile stress in the bolt.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Engineering Failure Analysis",
title = "Failure of mounting bolt of helicopter main gearbox support strut",
pages = "363-351",
volume = "70",
doi = "10.1016/j.engfailanal.2016.09.012"
}

Krstić, B., Rebhi, L., Ilić, N., Dodić, M., Dinulović, M., Andrić, P.,& Trifković, D.. (2016). Failure of mounting bolt of helicopter main gearbox support strut. in Engineering Failure Analysis
Pergamon-Elsevier Science Ltd, Oxford., 70, 351-363.
https://doi.org/10.1016/j.engfailanal.2016.09.012

Krstić B, Rebhi L, Ilić N, Dodić M, Dinulović M, Andrić P, Trifković D. Failure of mounting bolt of helicopter main gearbox support strut. in Engineering Failure Analysis. 2016;70:351-363.
doi:10.1016/j.engfailanal.2016.09.012 .

Krstić, Branimir, Rebhi, Lamine, Ilić, Nada, Dodić, Marjan, Dinulović, Mirko, Andrić, Predrag, Trifković, Dragan, "Failure of mounting bolt of helicopter main gearbox support strut" in Engineering Failure Analysis, 70 (2016):351-363,
https://doi.org/10.1016/j.engfailanal.2016.09.012 . .

TY  - JOUR
AU  - Krstić, Branimir
AU  - Rašuo, Boško
AU  - Trifković, Dragan
AU  - Radisavljević, Igor
AU  - Rajić, Zoran
AU  - Dinulović, Mirko
PY  - 2015
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/2078
AB  - Tokom leta školskog aviona Utva-75 došlo je do otkaza motora usled pucanja glave cilindra. Nakon uspešno izvršenog prinudnog sletanja oštećeni sklop cilindra je demontiran sa motora aviona i poslat na forenzičku ekspertizu. Fraktografskim ispitivanjem prelomne površine utvrđeno je da je uzrok otkaza zamor materijala glave cilindra. Metalografska ispitivanja pokazala su da je uzrok nastanka zamorne prsline postojanje značajne poroznosti materijala upravo u zoni nastanka loma. Numerička simulacija naponskog stanja sklopa cilindra, izvršena metodom konačnih elemenata, potvrdila je pretpostavku da je lom iniciran u zoni najveće koncentracije napona.
AB  - The piston engine of the training aircraft Utva-75 malfunctioned during the flight mission due to the cracking of its cylinder head. After successful forced landing, the damaged cylinder assembly was removed from the engine and sent to the lab for forensic expertise. Fractographic examination of the mating fracture surfaces revealed that the fatigue was the main cause of the cylinder head failure. The metallography examination has shown that the fatigue was promoted from pre-existing material defect due to an elevated presence of porosity forms at the crack initiation zone. The finite element method, utilized to determine the stress state of the cylinder assembly, confirmed that the crack origin was located at the most stress area.
PB  - Savez inženjera i tehničara Srbije, Beograd
T2  - Tehnika
T1  - Ispitivanje uzroka mehaničkog otkaza glave cilindra avionskog klipnog motora
T1  - Investigation of mechanical failure cause of an aircraft piston engine cylinder head
EP  - 80
IS  - 1
SP  - 71
VL  - 70
DO  - 10.5937/tehnika1501071K
ER  - 

@article{
author = "Krstić, Branimir and Rašuo, Boško and Trifković, Dragan and Radisavljević, Igor and Rajić, Zoran and Dinulović, Mirko",
year = "2015",
abstract = "Tokom leta školskog aviona Utva-75 došlo je do otkaza motora usled pucanja glave cilindra. Nakon uspešno izvršenog prinudnog sletanja oštećeni sklop cilindra je demontiran sa motora aviona i poslat na forenzičku ekspertizu. Fraktografskim ispitivanjem prelomne površine utvrđeno je da je uzrok otkaza zamor materijala glave cilindra. Metalografska ispitivanja pokazala su da je uzrok nastanka zamorne prsline postojanje značajne poroznosti materijala upravo u zoni nastanka loma. Numerička simulacija naponskog stanja sklopa cilindra, izvršena metodom konačnih elemenata, potvrdila je pretpostavku da je lom iniciran u zoni najveće koncentracije napona., The piston engine of the training aircraft Utva-75 malfunctioned during the flight mission due to the cracking of its cylinder head. After successful forced landing, the damaged cylinder assembly was removed from the engine and sent to the lab for forensic expertise. Fractographic examination of the mating fracture surfaces revealed that the fatigue was the main cause of the cylinder head failure. The metallography examination has shown that the fatigue was promoted from pre-existing material defect due to an elevated presence of porosity forms at the crack initiation zone. The finite element method, utilized to determine the stress state of the cylinder assembly, confirmed that the crack origin was located at the most stress area.",
publisher = "Savez inženjera i tehničara Srbije, Beograd",
journal = "Tehnika",
title = "Ispitivanje uzroka mehaničkog otkaza glave cilindra avionskog klipnog motora, Investigation of mechanical failure cause of an aircraft piston engine cylinder head",
pages = "80-71",
number = "1",
volume = "70",
doi = "10.5937/tehnika1501071K"
}

Krstić, B., Rašuo, B., Trifković, D., Radisavljević, I., Rajić, Z.,& Dinulović, M.. (2015). Ispitivanje uzroka mehaničkog otkaza glave cilindra avionskog klipnog motora. in Tehnika
Savez inženjera i tehničara Srbije, Beograd., 70(1), 71-80.
https://doi.org/10.5937/tehnika1501071K

Krstić B, Rašuo B, Trifković D, Radisavljević I, Rajić Z, Dinulović M. Ispitivanje uzroka mehaničkog otkaza glave cilindra avionskog klipnog motora. in Tehnika. 2015;70(1):71-80.
doi:10.5937/tehnika1501071K .

Krstić, Branimir, Rašuo, Boško, Trifković, Dragan, Radisavljević, Igor, Rajić, Zoran, Dinulović, Mirko, "Ispitivanje uzroka mehaničkog otkaza glave cilindra avionskog klipnog motora" in Tehnika, 70, no. 1 (2015):71-80,
https://doi.org/10.5937/tehnika1501071K . .

TY  - JOUR
AU  - Krstić, Branimir
AU  - Rašuo, Boško
AU  - Trifković, Dragan
AU  - Radisavljević, Igor
AU  - Rajić, Zoran
AU  - Dinulović, Mirko
PY  - 2013
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/1685
AB  - Cylinder head (CH) failures in aircraft piston engine may have serious or fatal consequences to the safety of the crew and the aircraft. Moreover, when failure becomes undoubtedly repetitive and critical resulting in loss of aircraft, destruction of properties, and first and foremost loss of human lives, the cause of the failure requires to be investigated using a scientific approach. Therefore, the aim of this study is to investigate and identify the root cause of a repetitive premature failure in an aircraft engine CH. The piston engine of the training aircraft Utva-75 has malfunctioned during the flight due to the cracking of its aluminum cast CH. It has been the second engine failure of this type of aircraft due to the cracking in the CH in a very short span of time. From the visual examination of the mating fracture surfaces, it has been possible to observe typical beach and ratchet marks indicating the occurrence of fatigue failure. The crack has initiated from multiple origins located on the inner flange fillet on the exhaust side of the CH. Further examinations by using scanning electron microscopy as well as energy dispersive spectroscopy and metallography have shown that the fatigue had promoted from pre-existing material defect due to a high concentration of shrinkage pores at the initiation crack site and can be most likely associated with the manufacturing process of casting. The stress analysis of the cylinder assembly, carried out by means of finite element analysis, has also confirmed that the crack origin was located at the most stressed area of the cylinder assembly i.e. on the inner flange fillet of the exhaust side of the CH. This case study, together with the other recently reported, has definitely confirmed the repetitive and therefore systematic problems with the CH of air cooled, horizontally opposed, aircraft piston engines.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Engineering Failure Analysis
T1  - An investigation of the repetitive failure in an aircraft engine cylinder head
EP  - 349
SP  - 335
VL  - 34
DO  - 10.1016/j.engfailanal.2013.08.013
ER  - 

@article{
author = "Krstić, Branimir and Rašuo, Boško and Trifković, Dragan and Radisavljević, Igor and Rajić, Zoran and Dinulović, Mirko",
year = "2013",
abstract = "Cylinder head (CH) failures in aircraft piston engine may have serious or fatal consequences to the safety of the crew and the aircraft. Moreover, when failure becomes undoubtedly repetitive and critical resulting in loss of aircraft, destruction of properties, and first and foremost loss of human lives, the cause of the failure requires to be investigated using a scientific approach. Therefore, the aim of this study is to investigate and identify the root cause of a repetitive premature failure in an aircraft engine CH. The piston engine of the training aircraft Utva-75 has malfunctioned during the flight due to the cracking of its aluminum cast CH. It has been the second engine failure of this type of aircraft due to the cracking in the CH in a very short span of time. From the visual examination of the mating fracture surfaces, it has been possible to observe typical beach and ratchet marks indicating the occurrence of fatigue failure. The crack has initiated from multiple origins located on the inner flange fillet on the exhaust side of the CH. Further examinations by using scanning electron microscopy as well as energy dispersive spectroscopy and metallography have shown that the fatigue had promoted from pre-existing material defect due to a high concentration of shrinkage pores at the initiation crack site and can be most likely associated with the manufacturing process of casting. The stress analysis of the cylinder assembly, carried out by means of finite element analysis, has also confirmed that the crack origin was located at the most stressed area of the cylinder assembly i.e. on the inner flange fillet of the exhaust side of the CH. This case study, together with the other recently reported, has definitely confirmed the repetitive and therefore systematic problems with the CH of air cooled, horizontally opposed, aircraft piston engines.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Engineering Failure Analysis",
title = "An investigation of the repetitive failure in an aircraft engine cylinder head",
pages = "349-335",
volume = "34",
doi = "10.1016/j.engfailanal.2013.08.013"
}

Krstić, B., Rašuo, B., Trifković, D., Radisavljević, I., Rajić, Z.,& Dinulović, M.. (2013). An investigation of the repetitive failure in an aircraft engine cylinder head. in Engineering Failure Analysis
Pergamon-Elsevier Science Ltd, Oxford., 34, 335-349.
https://doi.org/10.1016/j.engfailanal.2013.08.013

Krstić B, Rašuo B, Trifković D, Radisavljević I, Rajić Z, Dinulović M. An investigation of the repetitive failure in an aircraft engine cylinder head. in Engineering Failure Analysis. 2013;34:335-349.
doi:10.1016/j.engfailanal.2013.08.013 .

Krstić, Branimir, Rašuo, Boško, Trifković, Dragan, Radisavljević, Igor, Rajić, Zoran, Dinulović, Mirko, "An investigation of the repetitive failure in an aircraft engine cylinder head" in Engineering Failure Analysis, 34 (2013):335-349,
https://doi.org/10.1016/j.engfailanal.2013.08.013 . .

TY  - JOUR
AU  - Krstić, Branimir
AU  - Rašuo, Boško
AU  - Trifković, Dragan
AU  - Radisavljević, Igor
AU  - Rajić, Zoran
AU  - Dinulović, Mirko
PY  - 2013
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/1726
AB  - The piston engine of the training aircraft malfunctioned during the flight due to the cracking of its cylinder head (CH), which is manufactured from an aluminum casting alloy. Based on the fractographic examination of the mating fracture surfaces, the characteristic ratchet and beach marks were observed indicating the occurrence of fatigue failure. The crack was initiated from multiple origins located on the inner flange fillet on the exhaust side of the CH. The metallography examination has shown that the fatigue was promoted from preexisting material defect due to an elevated presence of shrinkage pores at the crack initiation zone and was most likely associated with the manufacturing process of casting. The finite element (FE) method, utilized to determine the stress state of the CH subjected to gas pressure, also confirmed that the crack origin was located at the most stress area.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Engineering Failure Analysis
T1  - Failure analysis of an aircraft engine cylinder head
EP  - 15
SP  - 1
VL  - 32
DO  - 10.1016/j.engfailanal.2013.03.004
ER  - 

@article{
author = "Krstić, Branimir and Rašuo, Boško and Trifković, Dragan and Radisavljević, Igor and Rajić, Zoran and Dinulović, Mirko",
year = "2013",
abstract = "The piston engine of the training aircraft malfunctioned during the flight due to the cracking of its cylinder head (CH), which is manufactured from an aluminum casting alloy. Based on the fractographic examination of the mating fracture surfaces, the characteristic ratchet and beach marks were observed indicating the occurrence of fatigue failure. The crack was initiated from multiple origins located on the inner flange fillet on the exhaust side of the CH. The metallography examination has shown that the fatigue was promoted from preexisting material defect due to an elevated presence of shrinkage pores at the crack initiation zone and was most likely associated with the manufacturing process of casting. The finite element (FE) method, utilized to determine the stress state of the CH subjected to gas pressure, also confirmed that the crack origin was located at the most stress area.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Engineering Failure Analysis",
title = "Failure analysis of an aircraft engine cylinder head",
pages = "15-1",
volume = "32",
doi = "10.1016/j.engfailanal.2013.03.004"
}

Krstić, B., Rašuo, B., Trifković, D., Radisavljević, I., Rajić, Z.,& Dinulović, M.. (2013). Failure analysis of an aircraft engine cylinder head. in Engineering Failure Analysis
Pergamon-Elsevier Science Ltd, Oxford., 32, 1-15.
https://doi.org/10.1016/j.engfailanal.2013.03.004

Krstić B, Rašuo B, Trifković D, Radisavljević I, Rajić Z, Dinulović M. Failure analysis of an aircraft engine cylinder head. in Engineering Failure Analysis. 2013;32:1-15.
doi:10.1016/j.engfailanal.2013.03.004 .

Krstić, Branimir, Rašuo, Boško, Trifković, Dragan, Radisavljević, Igor, Rajić, Zoran, Dinulović, Mirko, "Failure analysis of an aircraft engine cylinder head" in Engineering Failure Analysis, 32 (2013):1-15,
https://doi.org/10.1016/j.engfailanal.2013.03.004 . .

TY  - JOUR
AU  - Dinulović, Mirko
AU  - Rašuo, Boško
AU  - Krstić, Branimir
AU  - Bojanić, Aleksandar
AU  - Bojanić, A.
PY  - 2013
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/1752
AB  - Povećana upotreba kompozitnih materijala donela potrebu za razvojem pouzdanih i efikasnih tehnika popravki. Kao i sve druge noseće metalne strukture i kompozitne strukture sklone su oštećenjima. Razvijene tehnike popravki metalnih konstrukcije nisu direktno primenljive na kompozite i problem popravki kompozitnih struktura mora biti detaljno proučen. U ovom radu analizirana je primena kompozitnih materijala sa slučajnim rasporedom vlakana, kao materijalom za popravku oštećenih saćastih jezgara visoke gustine sendvič konstrukcija. Pomoću Panove teorije izveden je izraz potrebnog zapreminskog udela vlakana materijala popravke i određeno je kompletno naponsko deformaciono stanje popravljene kompozitne stukture metodom konačnih elemenata. Zaključeno je da kompozitni materijali sa slučajnim rasporedom vlakana predstavljaju veoma dobre kandidate za popravku oštećenih kompozitnih struktura sa saćastim jezgrima.
AB  - The increased use of composites has rendered the need for development of reliable and efficient repair techniques. Like all other metallic structures composite structures are prone to variety of damage. Repair techniques developed for metallic structures are not directly applicable to composites and problem of composite repair has to be investigated in great detail. In the present paper application of 3D random fiber polymer composites, as a repair material for damaged high density honeycomb cores in sandwich structures is investigated. Based on Pan 's theory the expression for matching fiber volume fraction of the repair material is derived and complete stress-strain field, of the repaired sandwich structure is determined using finite element approach. It is concluded that the 3D random fiber composites represent very good candidates as repair materials for damaged honeycomb structured composites.
PB  - Univerzitet u Beogradu - Mašinski fakultet, Beograd
T2  - FME Transactions
T1  - Kompozitni materijali sa slučajnim rasporedom vlakana kao materijali za popravku oštećenih saćastih jezgara
T1  - 3D random fiber composites as a repair material for damaged honeycomb cores
EP  - 332
IS  - 4
SP  - 325
VL  - 41
UR  - https://hdl.handle.net/21.15107/rcub_machinery_1752
ER  - 

@article{
author = "Dinulović, Mirko and Rašuo, Boško and Krstić, Branimir and Bojanić, Aleksandar and Bojanić, A.",
year = "2013",
abstract = "Povećana upotreba kompozitnih materijala donela potrebu za razvojem pouzdanih i efikasnih tehnika popravki. Kao i sve druge noseće metalne strukture i kompozitne strukture sklone su oštećenjima. Razvijene tehnike popravki metalnih konstrukcije nisu direktno primenljive na kompozite i problem popravki kompozitnih struktura mora biti detaljno proučen. U ovom radu analizirana je primena kompozitnih materijala sa slučajnim rasporedom vlakana, kao materijalom za popravku oštećenih saćastih jezgara visoke gustine sendvič konstrukcija. Pomoću Panove teorije izveden je izraz potrebnog zapreminskog udela vlakana materijala popravke i određeno je kompletno naponsko deformaciono stanje popravljene kompozitne stukture metodom konačnih elemenata. Zaključeno je da kompozitni materijali sa slučajnim rasporedom vlakana predstavljaju veoma dobre kandidate za popravku oštećenih kompozitnih struktura sa saćastim jezgrima., The increased use of composites has rendered the need for development of reliable and efficient repair techniques. Like all other metallic structures composite structures are prone to variety of damage. Repair techniques developed for metallic structures are not directly applicable to composites and problem of composite repair has to be investigated in great detail. In the present paper application of 3D random fiber polymer composites, as a repair material for damaged high density honeycomb cores in sandwich structures is investigated. Based on Pan 's theory the expression for matching fiber volume fraction of the repair material is derived and complete stress-strain field, of the repaired sandwich structure is determined using finite element approach. It is concluded that the 3D random fiber composites represent very good candidates as repair materials for damaged honeycomb structured composites.",
publisher = "Univerzitet u Beogradu - Mašinski fakultet, Beograd",
journal = "FME Transactions",
title = "Kompozitni materijali sa slučajnim rasporedom vlakana kao materijali za popravku oštećenih saćastih jezgara, 3D random fiber composites as a repair material for damaged honeycomb cores",
pages = "332-325",
number = "4",
volume = "41",
url = "https://hdl.handle.net/21.15107/rcub_machinery_1752"
}

Dinulović, M., Rašuo, B., Krstić, B., Bojanić, A.,& Bojanić, A.. (2013). Kompozitni materijali sa slučajnim rasporedom vlakana kao materijali za popravku oštećenih saćastih jezgara. in FME Transactions
Univerzitet u Beogradu - Mašinski fakultet, Beograd., 41(4), 325-332.
https://hdl.handle.net/21.15107/rcub_machinery_1752

Dinulović M, Rašuo B, Krstić B, Bojanić A, Bojanić A. Kompozitni materijali sa slučajnim rasporedom vlakana kao materijali za popravku oštećenih saćastih jezgara. in FME Transactions. 2013;41(4):325-332.
https://hdl.handle.net/21.15107/rcub_machinery_1752 .

Dinulović, Mirko, Rašuo, Boško, Krstić, Branimir, Bojanić, Aleksandar, Bojanić, A., "Kompozitni materijali sa slučajnim rasporedom vlakana kao materijali za popravku oštećenih saćastih jezgara" in FME Transactions, 41, no. 4 (2013):325-332,
https://hdl.handle.net/21.15107/rcub_machinery_1752 .

TY  - JOUR
AU  - Trifković, Dragan
AU  - Stupar, Slobodan
AU  - Bošnjak, Srđan
AU  - Milovančević, Milorad
AU  - Krstić, Branimir
AU  - Rajić, Zoran
AU  - Dunjić, Momčilo
PY  - 2011
UR  - https://machinery.mas.bg.ac.rs/handle/123456789/1199
AB  - This paper analyzes failure causes of the combat jet aircraft rudder shaft (RS) which occurred during the flight mission. A finite element method (FEM), utilized to determine the stress state of the RS subjected to hinge moment ultimate load, resulted in the high stress concentration sites around the rivet holes. The longitudinal crack was initiated from the corrosion pit in the zone of the rivet hole, where the fatigue beach marks were observed. The inner surface of the RS was heavily corroded. Moreover, pitting corrosion has destroyed approximately 50% of the wall thickness. Based on the presented results it was concluded that the failure of the RS had a character of fatigue combined with heavy corrosion. Therefore, it is recommended that the RS should be redesigned; the material changed into more corrosion resistant one and the maintenance procedure changed in order to avoid future similar failures.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Engineering Failure Analysis
T1  - Failure analysis of the combat jet aircraft rudder shaft
EP  - 2007
IS  - 8
SP  - 1998
VL  - 18
DO  - 10.1016/j.engfailanal.2011.05.017
ER  - 

@article{
author = "Trifković, Dragan and Stupar, Slobodan and Bošnjak, Srđan and Milovančević, Milorad and Krstić, Branimir and Rajić, Zoran and Dunjić, Momčilo",
year = "2011",
abstract = "This paper analyzes failure causes of the combat jet aircraft rudder shaft (RS) which occurred during the flight mission. A finite element method (FEM), utilized to determine the stress state of the RS subjected to hinge moment ultimate load, resulted in the high stress concentration sites around the rivet holes. The longitudinal crack was initiated from the corrosion pit in the zone of the rivet hole, where the fatigue beach marks were observed. The inner surface of the RS was heavily corroded. Moreover, pitting corrosion has destroyed approximately 50% of the wall thickness. Based on the presented results it was concluded that the failure of the RS had a character of fatigue combined with heavy corrosion. Therefore, it is recommended that the RS should be redesigned; the material changed into more corrosion resistant one and the maintenance procedure changed in order to avoid future similar failures.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Engineering Failure Analysis",
title = "Failure analysis of the combat jet aircraft rudder shaft",
pages = "2007-1998",
number = "8",
volume = "18",
doi = "10.1016/j.engfailanal.2011.05.017"
}

Trifković, D., Stupar, S., Bošnjak, S., Milovančević, M., Krstić, B., Rajić, Z.,& Dunjić, M.. (2011). Failure analysis of the combat jet aircraft rudder shaft. in Engineering Failure Analysis
Pergamon-Elsevier Science Ltd, Oxford., 18(8), 1998-2007.
https://doi.org/10.1016/j.engfailanal.2011.05.017

Trifković D, Stupar S, Bošnjak S, Milovančević M, Krstić B, Rajić Z, Dunjić M. Failure analysis of the combat jet aircraft rudder shaft. in Engineering Failure Analysis. 2011;18(8):1998-2007.
doi:10.1016/j.engfailanal.2011.05.017 .

Trifković, Dragan, Stupar, Slobodan, Bošnjak, Srđan, Milovančević, Milorad, Krstić, Branimir, Rajić, Zoran, Dunjić, Momčilo, "Failure analysis of the combat jet aircraft rudder shaft" in Engineering Failure Analysis, 18, no. 8 (2011):1998-2007,
https://doi.org/10.1016/j.engfailanal.2011.05.017 . .