2012
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Nonn, A.; Kalwa, C. Simulation of ductile crack propagation in high-strength pipeline steel using damage models Werkstoffsimulation Proceedings Article In: 9th International Pipeline Conference 2012 (IPC 2012), Calgary, Canada, 2012. @inproceedings{Nonn2012,
title = {Simulation of ductile crack propagation in high-strength pipeline steel using damage models},
author = {A. Nonn and C. Kalwa},
year = {2012},
date = {2012-09-24},
booktitle = {9th International Pipeline Conference 2012 (IPC 2012)},
address = {Calgary, Canada},
abstract = {The performance of engineering design of high-strength steel pipelines has revealed the necessity to revise current design procedures. Therefore, an improved and detailed comprehension of fracture mechanisms and development of failure prediction tools are required in order to derive new design criteria. In last decades the most successful failure prediction tools for steel structures subjected to various type of loading can be encountered in the field of damage mechanics. This paper aims to describe ductile fracture behavior of high-strength steel pipelines by applying three different damage models, Gurson-Tvergaard-Needelman (GTN), Fracture Locus Curve (FLC) and Cohesive Zone (CZ). These models are evaluated regarding their capability to estimate ductile crack propagation in laboratory specimens and linepipe components without adjusting the calibrated parameters. It can be shown that appropriate parameter sets can be identified to reproduce load-deformation and fracture resistance curves accurately. The strain rate effect on the fracture behavior is examined by dynamic tests on the BDWT specimens. Finally, the shortcomings of the applied models are pointed out with the reference to possible extensions and modifications.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
The performance of engineering design of high-strength steel pipelines has revealed the necessity to revise current design procedures. Therefore, an improved and detailed comprehension of fracture mechanisms and development of failure prediction tools are required in order to derive new design criteria. In last decades the most successful failure prediction tools for steel structures subjected to various type of loading can be encountered in the field of damage mechanics. This paper aims to describe ductile fracture behavior of high-strength steel pipelines by applying three different damage models, Gurson-Tvergaard-Needelman (GTN), Fracture Locus Curve (FLC) and Cohesive Zone (CZ). These models are evaluated regarding their capability to estimate ductile crack propagation in laboratory specimens and linepipe components without adjusting the calibrated parameters. It can be shown that appropriate parameter sets can be identified to reproduce load-deformation and fracture resistance curves accurately. The strain rate effect on the fracture behavior is examined by dynamic tests on the BDWT specimens. Finally, the shortcomings of the applied models are pointed out with the reference to possible extensions and modifications. |
Kofiani, K.; Nonn, A.; Wierzbicki, T.; Kalwa, C.; Walters, C. Experiments and fracture modeling of high-strength pipelines for high and low stress triaxiality Werkstoffsimulation Proceedings Article In: The 22nd International Society of Offshore and Polar Engineering 2012 (ISOPE 2012), Rhodes, Greece, 2012. @inproceedings{Kofiani2012,
title = {Experiments and fracture modeling of high-strength pipelines for high and low stress triaxiality},
author = {K. Kofiani and A. Nonn and T. Wierzbicki and C. Kalwa and C. Walters},
year = {2012},
date = {2012-06-17},
booktitle = {The 22nd International Society of Offshore and Polar Engineering 2012 (ISOPE 2012)},
address = {Rhodes, Greece},
abstract = {This paper provides results from a comprehensive study on mechanical characterization of high-strength pipeline steel, grade X100 using experimental and numerical methods. The material was characterized for anisotropic plasticity, fracture initiation for various states of stress, (pre-cracked) fracture toughness and uncracked ductility. The experimental program included tests on flat butterfly-shaped, central hole, notched and circular disk specimens for low stress triaxiality levels; as well as tests on round notched bar specimens and SENT fracture mechanics tests, for high values of stress triaxiality. This program covered a wide range of stress conditions and demonstrated its effect on the material resistance. Parallel to the experimental study, detailed numerical investigations were carried out to simulate all different experimental tests. Using an inverse method, a 3-parameter calibration was performed on the Modified Mohr-Coulomb (MMC) fracture model. Subsequently, the predictive capabilities of the MMC were evaluated by the comparison to the fracture toughness tests results, used extensively in the pipeline industry. The capabilities of the MIT fracture model have been demonstrated on an example of high strength offshore steel, X100. The outcome of this study was not only to provide, the overall characterization of the fracture behavior of this material as an example, but also to present the methodology on how to use the MMC model as a practical tool in pipeline design.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
This paper provides results from a comprehensive study on mechanical characterization of high-strength pipeline steel, grade X100 using experimental and numerical methods. The material was characterized for anisotropic plasticity, fracture initiation for various states of stress, (pre-cracked) fracture toughness and uncracked ductility. The experimental program included tests on flat butterfly-shaped, central hole, notched and circular disk specimens for low stress triaxiality levels; as well as tests on round notched bar specimens and SENT fracture mechanics tests, for high values of stress triaxiality. This program covered a wide range of stress conditions and demonstrated its effect on the material resistance. Parallel to the experimental study, detailed numerical investigations were carried out to simulate all different experimental tests. Using an inverse method, a 3-parameter calibration was performed on the Modified Mohr-Coulomb (MMC) fracture model. Subsequently, the predictive capabilities of the MMC were evaluated by the comparison to the fracture toughness tests results, used extensively in the pipeline industry. The capabilities of the MIT fracture model have been demonstrated on an example of high strength offshore steel, X100. The outcome of this study was not only to provide, the overall characterization of the fracture behavior of this material as an example, but also to present the methodology on how to use the MMC model as a practical tool in pipeline design. |
Nonn, A.; Kalwa, C. Failure modeling of pipeline X100 Material in temperature transition region Werkstoffsimulation Proceedings Article In: The 22nd International Society of Offshore and Polar Engineering 2012 (ISOPE 2012), Rhodes, Greece, 2012. @inproceedings{Nonn2012b,
title = {Failure modeling of pipeline X100 Material in temperature transition region},
author = {A. Nonn and C. Kalwa},
year = {2012},
date = {2012-06-17},
booktitle = {The 22nd International Society of Offshore and Polar Engineering 2012 (ISOPE 2012)},
address = {Rhodes, Greece},
abstract = {This paper focuses on the characterization of the fracture performance of X100 material in transition temperature region using both experimental and numerical methods. The ductile fracture has been analyzed using tests on round notched bar specimens and standard fracture mechanics tests performed at room temperature. In previous publications the damage model Gurson-Tvergaard-Needleman (GTN) has been applied and verified by existing experimental data to describe ductile fracture behavior. The brittle fracture and the fracture in temperature transition region have been studied by means of deep and shallow notched SENB specimens at two different temperatures T=-80°C and -40°C. Besides elastic-plastic analyses to quantify constraint levels for different initial crack configurations at the onset of cleavage fracture, the brittle failure has been described using modified Beremin model. The influence of the stable crack growth on the cleavage failure probability in temperature transition region has been captured by coupling the ductile fracture model (GTN) with the modified Beremin model. Finally, examples have been presented for the practical application of the numerical results on the fracture assessment of the flawed high-strength pipelines.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
This paper focuses on the characterization of the fracture performance of X100 material in transition temperature region using both experimental and numerical methods. The ductile fracture has been analyzed using tests on round notched bar specimens and standard fracture mechanics tests performed at room temperature. In previous publications the damage model Gurson-Tvergaard-Needleman (GTN) has been applied and verified by existing experimental data to describe ductile fracture behavior. The brittle fracture and the fracture in temperature transition region have been studied by means of deep and shallow notched SENB specimens at two different temperatures T=-80°C and -40°C. Besides elastic-plastic analyses to quantify constraint levels for different initial crack configurations at the onset of cleavage fracture, the brittle failure has been described using modified Beremin model. The influence of the stable crack growth on the cleavage failure probability in temperature transition region has been captured by coupling the ductile fracture model (GTN) with the modified Beremin model. Finally, examples have been presented for the practical application of the numerical results on the fracture assessment of the flawed high-strength pipelines. |
2011
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Nonn, A.; Kalwa, C. The effect of microstructure, strain hardening and strain rate on the fracture behavior of high strength pipeline steels Werkstoffsimulation Proceedings Article In: 2nd International Conference on Material Modelling (ICMM2), Paris, France, 2011. @inproceedings{,
title = {The effect of microstructure, strain hardening and strain rate on the fracture behavior of high strength pipeline steels},
author = {A. Nonn and C. Kalwa},
year = {2011},
date = {2011-08-31},
booktitle = {2nd International Conference on Material Modelling (ICMM2)},
address = {Paris, France},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
|
2010
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Nonn, A. Failure modeling of hybrid-laser welds in transition temperature region Werkstoffsimulation Proceedings Article In: Fracture of Materials and Structures from Micro to Macro Scale, 18th European Conference on Fracture, Dresden, Germany, 2010. @inproceedings{,
title = {Failure modeling of hybrid-laser welds in transition temperature region},
author = {A. Nonn},
year = {2010},
date = {2010-08-30},
booktitle = {Fracture of Materials and Structures from Micro to Macro Scale, 18th European Conference on Fracture},
address = {Dresden, Germany},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
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