TY  - JOUR
AU  - Trajković, Isaak
AU  - Rakin, Marko
AU  - Milošević, Miloš
AU  - Mitrović, Nenad
AU  - Travica, Milan
AU  - Sedmak, Aleksandar
AU  - Međo, Bojan
PY  - 2023
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/6649
AB  - In order to develop a non-standard method for determining the resistance to fracture and damage of pipeline materials, a new geometry of ring-shaped specimens with sharp notches or cracks has been defined. The need to develop a new method for testing of the specimens cut from the pipes arises due to the difficulties in determination of fracture mechanics parameters on thin-walled pressure pipelines, especially those with a smaller cross-section, by application of the standard procedures/specimens. Previous studies dealing with the topic of pipeline testing by non-standard methods are presented in the introductory part of the paper. In the experimental part of the research, tests on PRNT (Pipe Ring Notched Tension) and SENT (Single Edge Notched Tension) specimens are performed. Samples of these specimens were produced by SLS (Selective Laser Sintering) technique of additive production from PA12 (polyamide PA 2200) material. For the purpose of this study, a tool that is protected at the national level (in Serbia) as intellectual property is used for testing of the ring-shaped PRNT specimens. Tensile testing of both types of specimens is monitored by Aramis GOM 2M system; its operation is based on the method of digital image correlation, DIC. Additionally, finite element analyses are conducted on the PRNT and SENT geometries, enabling the calculation of the fracture mechanics parameter – Stress intensity factor K. It is concluded that the presented procedure based on the PRNT specimen has a good potential for use as a non-standard method for fracture resistance examination of pipeline materials. It can be performed on the specimens cut directly from the pipes (new or from exploitation). The dependence of the fracture resistance on the stress concentrator size is not pronounced, which means that the results depend dominantly on the material properties, rather than on geometry.
PB  - Elsevier Ltd.
T2  - Engineering Fracture Mechanics
T1  - Selective laser sintered Pipe Ring Notched Tension specimens for examination of fracture properties of pipeline materials
SP  - 109573
VL  - 292
DO  - 10.1016/j.engfracmech.2023.109573
ER  - 

@article{
author = "Trajković, Isaak and Rakin, Marko and Milošević, Miloš and Mitrović, Nenad and Travica, Milan and Sedmak, Aleksandar and Međo, Bojan",
year = "2023",
abstract = "In order to develop a non-standard method for determining the resistance to fracture and damage of pipeline materials, a new geometry of ring-shaped specimens with sharp notches or cracks has been defined. The need to develop a new method for testing of the specimens cut from the pipes arises due to the difficulties in determination of fracture mechanics parameters on thin-walled pressure pipelines, especially those with a smaller cross-section, by application of the standard procedures/specimens. Previous studies dealing with the topic of pipeline testing by non-standard methods are presented in the introductory part of the paper. In the experimental part of the research, tests on PRNT (Pipe Ring Notched Tension) and SENT (Single Edge Notched Tension) specimens are performed. Samples of these specimens were produced by SLS (Selective Laser Sintering) technique of additive production from PA12 (polyamide PA 2200) material. For the purpose of this study, a tool that is protected at the national level (in Serbia) as intellectual property is used for testing of the ring-shaped PRNT specimens. Tensile testing of both types of specimens is monitored by Aramis GOM 2M system; its operation is based on the method of digital image correlation, DIC. Additionally, finite element analyses are conducted on the PRNT and SENT geometries, enabling the calculation of the fracture mechanics parameter – Stress intensity factor K. It is concluded that the presented procedure based on the PRNT specimen has a good potential for use as a non-standard method for fracture resistance examination of pipeline materials. It can be performed on the specimens cut directly from the pipes (new or from exploitation). The dependence of the fracture resistance on the stress concentrator size is not pronounced, which means that the results depend dominantly on the material properties, rather than on geometry.",
publisher = "Elsevier Ltd.",
journal = "Engineering Fracture Mechanics",
title = "Selective laser sintered Pipe Ring Notched Tension specimens for examination of fracture properties of pipeline materials",
pages = "109573",
volume = "292",
doi = "10.1016/j.engfracmech.2023.109573"
}

Trajković, I., Rakin, M., Milošević, M., Mitrović, N., Travica, M., Sedmak, A.,& Međo, B.. (2023). Selective laser sintered Pipe Ring Notched Tension specimens for examination of fracture properties of pipeline materials. in Engineering Fracture Mechanics
Elsevier Ltd.., 292, 109573.
https://doi.org/10.1016/j.engfracmech.2023.109573

Trajković I, Rakin M, Milošević M, Mitrović N, Travica M, Sedmak A, Međo B. Selective laser sintered Pipe Ring Notched Tension specimens for examination of fracture properties of pipeline materials. in Engineering Fracture Mechanics. 2023;292:109573.
doi:10.1016/j.engfracmech.2023.109573 .

Trajković, Isaak, Rakin, Marko, Milošević, Miloš, Mitrović, Nenad, Travica, Milan, Sedmak, Aleksandar, Međo, Bojan, "Selective laser sintered Pipe Ring Notched Tension specimens for examination of fracture properties of pipeline materials" in Engineering Fracture Mechanics, 292 (2023):109573,
https://doi.org/10.1016/j.engfracmech.2023.109573 . .

TY  - JOUR
AU  - Matić, Tamara
AU  - Ležaja Zebić, Maja
AU  - Miletić, Vesna
AU  - Trajković, Isaak
AU  - Milošević, Miloš
AU  - Racić, Aleksandar
AU  - Veljović, Đorđe
PY  - 2023
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/6659
AB  - This study aimed to (1) comparatively analyze properties of Sr- and Mg-substituted
hydroxyapatite (HAP)-based dental inserts; (2) evaluate insert bonding to restorative
materials, and (3) evaluate the effect of doped HAP inserts on fracture resistance
(FR) of human molars with large occlusal restorations. By ion-doping with Sr or Mg,
3 insert types were obtained and characterized using XRD, SEM, Vickers hardness and
fracture toughness. Shear bond strength (SBS) was determined between acid etched or
unetched inserts and following materials: Maxcem cement (Kerr); Filtek Z250
(3M) bonded with Single Bond Universal (SBU; 3M) or Clearfil Universal (Cf; Kuraray).
Modified Class I cavities were prepared in 16 intact molars and restored using insert
+ composite or composite only (control) (n = 8/group). FR of restored molars was
determined by static load until fracture upon thermal cycling. Fracture toughness was
similar between Sr/Mg-doped inserts (0.94–1.04 MPam 1/2 p = .429). Mg-doped
inserts showed greater hardness (range 4.78–5.15 GPa) than Sr6 inserts (3.74
± 0.31 GPa; p < .05). SBS for SBU and Cf adhesives (range 7.19–15.93 MPa) was higher
than for Maxcem (range 3.07–5.95 MPa) (p < .05). There was no significant difference
in FR between molars restored with insert-containing and control restorations (3.00
± 0.30 kN and 3.22 ± 0.42 kN, respectively; p > .05). HAP-based inserts doped with
Mg/Sr had different composition and mechanical properties. Adhesive bonding to
inserts resulted in greater bond strength than cementation, which may be improved by
insert acid-etching. Ion-doped HAP inserts did not affect FR of restored molars. In conclusion,
HAP-based dental inserts may potentially replace dentin in large cavities, without
affecting fracture resistance of restored teeth.
PB  - Wiley Periodicals LLC.
T2  - Journal of Biomedical Materials Research Part B: Applied Biomaterials
T1  - Hydroxyapatite-based dental inserts: microstructure, mechanical properties, bonding efficiency and fracture resistance of molars with occlusal restorations
DO  - 10.1002/jbm.b.35331
ER  - 

@article{
author = "Matić, Tamara and Ležaja Zebić, Maja and Miletić, Vesna and Trajković, Isaak and Milošević, Miloš and Racić, Aleksandar and Veljović, Đorđe",
year = "2023",
abstract = "This study aimed to (1) comparatively analyze properties of Sr- and Mg-substituted
hydroxyapatite (HAP)-based dental inserts; (2) evaluate insert bonding to restorative
materials, and (3) evaluate the effect of doped HAP inserts on fracture resistance
(FR) of human molars with large occlusal restorations. By ion-doping with Sr or Mg,
3 insert types were obtained and characterized using XRD, SEM, Vickers hardness and
fracture toughness. Shear bond strength (SBS) was determined between acid etched or
unetched inserts and following materials: Maxcem cement (Kerr); Filtek Z250
(3M) bonded with Single Bond Universal (SBU; 3M) or Clearfil Universal (Cf; Kuraray).
Modified Class I cavities were prepared in 16 intact molars and restored using insert
+ composite or composite only (control) (n = 8/group). FR of restored molars was
determined by static load until fracture upon thermal cycling. Fracture toughness was
similar between Sr/Mg-doped inserts (0.94–1.04 MPam 1/2 p = .429). Mg-doped
inserts showed greater hardness (range 4.78–5.15 GPa) than Sr6 inserts (3.74
± 0.31 GPa; p < .05). SBS for SBU and Cf adhesives (range 7.19–15.93 MPa) was higher
than for Maxcem (range 3.07–5.95 MPa) (p < .05). There was no significant difference
in FR between molars restored with insert-containing and control restorations (3.00
± 0.30 kN and 3.22 ± 0.42 kN, respectively; p > .05). HAP-based inserts doped with
Mg/Sr had different composition and mechanical properties. Adhesive bonding to
inserts resulted in greater bond strength than cementation, which may be improved by
insert acid-etching. Ion-doped HAP inserts did not affect FR of restored molars. In conclusion,
HAP-based dental inserts may potentially replace dentin in large cavities, without
affecting fracture resistance of restored teeth.",
publisher = "Wiley Periodicals LLC.",
journal = "Journal of Biomedical Materials Research Part B: Applied Biomaterials",
title = "Hydroxyapatite-based dental inserts: microstructure, mechanical properties, bonding efficiency and fracture resistance of molars with occlusal restorations",
doi = "10.1002/jbm.b.35331"
}

Matić, T., Ležaja Zebić, M., Miletić, V., Trajković, I., Milošević, M., Racić, A.,& Veljović, Đ.. (2023). Hydroxyapatite-based dental inserts: microstructure, mechanical properties, bonding efficiency and fracture resistance of molars with occlusal restorations. in Journal of Biomedical Materials Research Part B: Applied Biomaterials
Wiley Periodicals LLC...
https://doi.org/10.1002/jbm.b.35331

Matić T, Ležaja Zebić M, Miletić V, Trajković I, Milošević M, Racić A, Veljović Đ. Hydroxyapatite-based dental inserts: microstructure, mechanical properties, bonding efficiency and fracture resistance of molars with occlusal restorations. in Journal of Biomedical Materials Research Part B: Applied Biomaterials. 2023;.
doi:10.1002/jbm.b.35331 .

Matić, Tamara, Ležaja Zebić, Maja, Miletić, Vesna, Trajković, Isaak, Milošević, Miloš, Racić, Aleksandar, Veljović, Đorđe, "Hydroxyapatite-based dental inserts: microstructure, mechanical properties, bonding efficiency and fracture resistance of molars with occlusal restorations" in Journal of Biomedical Materials Research Part B: Applied Biomaterials (2023),
https://doi.org/10.1002/jbm.b.35331 . .

TY  - CONF
AU  - Trajković, Isaak
AU  - Milošević, Miloš
AU  - Travica, Milan
AU  - Rakin, Marko
AU  - Jevtić, Ivana
AU  - Sedmak, Aleksandar
AU  - Međo, Bojan
PY  - 2022
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/6010
AB  - This work presents the fabrication and tensile testing of polyamide specimens fabricated by
selective laser sintering (SLS). Two geometries are considered: SENT (Single Edge Notched
Tension) and PRNT (Pipe Ring Notched Tension) specimens. Experimental testing of these
specimens is a step in development of a new method for testing of properties of the pipeline
materials. The samples were produced by SLS (Selective Laser Sintering) additive production
technique. The samples were made from polyamide PA12 on EOS Formiga P100 machine
(fabrication parameters: laser power 30 W, print layer height 0.1 mm, scanning speed 1.6-5
m/s, operating temperature 170⁰C). Testing was performed in the displacement control on a
universal tensile testing machine Shimadzu AGS - X. On this machine, the values of force as
well as the values of stress and strain were obtained directly from the Trapezium X software.
Special attention in this work is devoted to two important aspects: fixing of the ring specimen
for testing and influence of friction between the specimen and the tool. The results obtained
on the examined specimens indicate that this study is a valuable contribution for further
development and verification of the new fracture resistance testing procedure for different
pipeline materials.
PB  - Serbian Academy of Sciences and Arts
C3  - Serbian Ceramic Society Conference ADVANCED CERAMICS AND APPLICATION X New Frontiers in Multifunctional Material Science and Processing
T1  - Laser sintered polyamide specimens - fabrication and tensile testing conditions on different geometries
SP  - 80
UR  - https://hdl.handle.net/21.15107/rcub_technorep_6010
ER  - 

@conference{
author = "Trajković, Isaak and Milošević, Miloš and Travica, Milan and Rakin, Marko and Jevtić, Ivana and Sedmak, Aleksandar and Međo, Bojan",
year = "2022",
abstract = "This work presents the fabrication and tensile testing of polyamide specimens fabricated by
selective laser sintering (SLS). Two geometries are considered: SENT (Single Edge Notched
Tension) and PRNT (Pipe Ring Notched Tension) specimens. Experimental testing of these
specimens is a step in development of a new method for testing of properties of the pipeline
materials. The samples were produced by SLS (Selective Laser Sintering) additive production
technique. The samples were made from polyamide PA12 on EOS Formiga P100 machine
(fabrication parameters: laser power 30 W, print layer height 0.1 mm, scanning speed 1.6-5
m/s, operating temperature 170⁰C). Testing was performed in the displacement control on a
universal tensile testing machine Shimadzu AGS - X. On this machine, the values of force as
well as the values of stress and strain were obtained directly from the Trapezium X software.
Special attention in this work is devoted to two important aspects: fixing of the ring specimen
for testing and influence of friction between the specimen and the tool. The results obtained
on the examined specimens indicate that this study is a valuable contribution for further
development and verification of the new fracture resistance testing procedure for different
pipeline materials.",
publisher = "Serbian Academy of Sciences and Arts",
journal = "Serbian Ceramic Society Conference ADVANCED CERAMICS AND APPLICATION X New Frontiers in Multifunctional Material Science and Processing",
title = "Laser sintered polyamide specimens - fabrication and tensile testing conditions on different geometries",
pages = "80",
url = "https://hdl.handle.net/21.15107/rcub_technorep_6010"
}

Trajković, I., Milošević, M., Travica, M., Rakin, M., Jevtić, I., Sedmak, A.,& Međo, B.. (2022). Laser sintered polyamide specimens - fabrication and tensile testing conditions on different geometries. in Serbian Ceramic Society Conference ADVANCED CERAMICS AND APPLICATION X New Frontiers in Multifunctional Material Science and Processing
Serbian Academy of Sciences and Arts., 80.
https://hdl.handle.net/21.15107/rcub_technorep_6010

Trajković I, Milošević M, Travica M, Rakin M, Jevtić I, Sedmak A, Međo B. Laser sintered polyamide specimens - fabrication and tensile testing conditions on different geometries. in Serbian Ceramic Society Conference ADVANCED CERAMICS AND APPLICATION X New Frontiers in Multifunctional Material Science and Processing. 2022;:80.
https://hdl.handle.net/21.15107/rcub_technorep_6010 .

Trajković, Isaak, Milošević, Miloš, Travica, Milan, Rakin, Marko, Jevtić, Ivana, Sedmak, Aleksandar, Međo, Bojan, "Laser sintered polyamide specimens - fabrication and tensile testing conditions on different geometries" in Serbian Ceramic Society Conference ADVANCED CERAMICS AND APPLICATION X New Frontiers in Multifunctional Material Science and Processing (2022):80,
https://hdl.handle.net/21.15107/rcub_technorep_6010 .

TY  - CONF
AU  - Trajković, Isaak
AU  - Milošević, Miloš
AU  - Rakin, Marko
AU  - Sedmak, Aleksandar
AU  - Međo, Bojan
PY  - 2022
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/6421
AB  - In order to define a procedure for integrity assessment of pipelines and determining the fracture mechanics parameters, a new type of specimen with a sharp notch, Pipe Ring Notched Tension (PRNT) specimen, is tested. The aim of the study is to determine the influence of the specimen geometry (cylindrical shape, as well as number and length of stress concentrators) on parameters such as force, Crack Mouth Opening Displacement CMOD, Crack Tip Opening Displacement CTOD and J integral. The specimens were fabricated by an additive production method - selective laser sintering (SLS). EOS Formiga P100 machine is used, and the material is polyamide PA12. In addition to Pipe Ring Notched Tension specimens, Single Edge Notched Tension (SENT) specimens with identical cross section were also considered. All specimens were tested on a universal tensile testing machine. A tool specially designed to apply contact pressure to the inner walls in the tension direction was used, simulating the internal pressure. For determining the field of displacement and strain on the surface of the tested samples that occur during the loading, Aramis GOM 2M optical measurement system was used. Aramis is applied for determination of geometry fracture mechanics parameters: CMOD and CTOD (based on δ5 concept). In addition to the examination of fracture properties of additively manufactured PA12, the main topic of this work is the development of the non-standard testing procedure, which will be subsequently applied to the specimens cut from metallic or non-metallic pipes. As an important part of this procedure, the calculation of fracture parameters will be conducted based on the results presented here.
PB  - Elsevier B.V.
C3  - Procedia Structural Integrity
T1  - Additively manufactured tensile ring-shaped specimens for pipeline material fracture examination - influence of geometry
EP  - 1319
SP  - 1314
VL  - 42
DO  - 10.1016/j.prostr.2022.12.167
ER  - 

@conference{
author = "Trajković, Isaak and Milošević, Miloš and Rakin, Marko and Sedmak, Aleksandar and Međo, Bojan",
year = "2022",
abstract = "In order to define a procedure for integrity assessment of pipelines and determining the fracture mechanics parameters, a new type of specimen with a sharp notch, Pipe Ring Notched Tension (PRNT) specimen, is tested. The aim of the study is to determine the influence of the specimen geometry (cylindrical shape, as well as number and length of stress concentrators) on parameters such as force, Crack Mouth Opening Displacement CMOD, Crack Tip Opening Displacement CTOD and J integral. The specimens were fabricated by an additive production method - selective laser sintering (SLS). EOS Formiga P100 machine is used, and the material is polyamide PA12. In addition to Pipe Ring Notched Tension specimens, Single Edge Notched Tension (SENT) specimens with identical cross section were also considered. All specimens were tested on a universal tensile testing machine. A tool specially designed to apply contact pressure to the inner walls in the tension direction was used, simulating the internal pressure. For determining the field of displacement and strain on the surface of the tested samples that occur during the loading, Aramis GOM 2M optical measurement system was used. Aramis is applied for determination of geometry fracture mechanics parameters: CMOD and CTOD (based on δ5 concept). In addition to the examination of fracture properties of additively manufactured PA12, the main topic of this work is the development of the non-standard testing procedure, which will be subsequently applied to the specimens cut from metallic or non-metallic pipes. As an important part of this procedure, the calculation of fracture parameters will be conducted based on the results presented here.",
publisher = "Elsevier B.V.",
journal = "Procedia Structural Integrity",
title = "Additively manufactured tensile ring-shaped specimens for pipeline material fracture examination - influence of geometry",
pages = "1319-1314",
volume = "42",
doi = "10.1016/j.prostr.2022.12.167"
}

Trajković, I., Milošević, M., Rakin, M., Sedmak, A.,& Međo, B.. (2022). Additively manufactured tensile ring-shaped specimens for pipeline material fracture examination - influence of geometry. in Procedia Structural Integrity
Elsevier B.V.., 42, 1314-1319.
https://doi.org/10.1016/j.prostr.2022.12.167

Trajković I, Milošević M, Rakin M, Sedmak A, Međo B. Additively manufactured tensile ring-shaped specimens for pipeline material fracture examination - influence of geometry. in Procedia Structural Integrity. 2022;42:1314-1319.
doi:10.1016/j.prostr.2022.12.167 .

Trajković, Isaak, Milošević, Miloš, Rakin, Marko, Sedmak, Aleksandar, Međo, Bojan, "Additively manufactured tensile ring-shaped specimens for pipeline material fracture examination - influence of geometry" in Procedia Structural Integrity, 42 (2022):1314-1319,
https://doi.org/10.1016/j.prostr.2022.12.167 . .