Nonn, A.; Kalwa, C. Analysis of dynamic ductile fracture propagation in pipeline steels: a damage mechanics approach Werkstoffsimulation Proceedings Article In: The 6th Pipeline Technology Conference (2013), Ostend, Belgium, 2013. @inproceedings{Nonn2013b,
title = {Analysis of dynamic ductile fracture propagation in pipeline steels: a damage mechanics approach},
author = {A. Nonn and C. Kalwa},
year = {2013},
date = {2013-10-07},
booktitle = {The 6th Pipeline Technology Conference (2013)},
address = {Ostend, Belgium},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
|
Nonn, A.; Wessel, W.; Schmidt, T. Application of finite element analysis for assessment of fracture behavior of modern high toughness seamless pipeline steels Werkstoffsimulation Proceedings Article In: The 23rd International Society of Offshore and Polar Engineering 2013 (ISOPE 2013), Anchorage, USA, 2013. @inproceedings{Nonn2013d,
title = {Application of finite element analysis for assessment of fracture behavior of modern high toughness seamless pipeline steels},
author = {A. Nonn and W. Wessel and T. Schmidt},
year = {2013},
date = {2013-06-30},
booktitle = {The 23rd International Society of Offshore and Polar Engineering 2013 (ISOPE 2013)},
address = {Anchorage, USA},
abstract = {Fracture behavior of seamless pipeline material X65Q acc. to API 5L has been studied both experimentally and numerically at different loading conditions (quasi-static vs. dynamic) and temperatures. The recent findings have shown difficulties in applying well established methods for determination of transition behavior or prediction of ductile crack arrest for the new generation of high-toughness steels. The irregular fracture performance (e.g. so-called "abnormal inverse fracture" appearance, significant scattering in ductile-to-brittle-transition-temperature region, etc.) suggests that the influence of pipe dimensions, loading parameters, crack initiation resistance as well as testing procedure on the fracture behavior has been neither understood nor properly described. This work aims to shed light on these questions regarding the applicability of conventional methods and to better illuminate most relevant parameters affecting fracture behavior of high toughness steels. To achieve this goal, experimental data basis for analysis of fracture behavior in transition and upper shelf regime has been established by conducting quasi-static fracture mechanics tests and dynamic tests on Battelle Drop Weight Tear (BDWT or DWT) specimens at different temperatures. The evaluation of obtained test results in upper shelf has been additionally complemented by numerical simulation of damage behavior. The results highlight the influence of stress conditions on fracture behavior with reference to pipe dimensions and loading conditions and, subsequently, may be used as a basis for revision of existing design methods.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Fracture behavior of seamless pipeline material X65Q acc. to API 5L has been studied both experimentally and numerically at different loading conditions (quasi-static vs. dynamic) and temperatures. The recent findings have shown difficulties in applying well established methods for determination of transition behavior or prediction of ductile crack arrest for the new generation of high-toughness steels. The irregular fracture performance (e.g. so-called "abnormal inverse fracture" appearance, significant scattering in ductile-to-brittle-transition-temperature region, etc.) suggests that the influence of pipe dimensions, loading parameters, crack initiation resistance as well as testing procedure on the fracture behavior has been neither understood nor properly described. This work aims to shed light on these questions regarding the applicability of conventional methods and to better illuminate most relevant parameters affecting fracture behavior of high toughness steels. To achieve this goal, experimental data basis for analysis of fracture behavior in transition and upper shelf regime has been established by conducting quasi-static fracture mechanics tests and dynamic tests on Battelle Drop Weight Tear (BDWT or DWT) specimens at different temperatures. The evaluation of obtained test results in upper shelf has been additionally complemented by numerical simulation of damage behavior. The results highlight the influence of stress conditions on fracture behavior with reference to pipe dimensions and loading conditions and, subsequently, may be used as a basis for revision of existing design methods. |
Nonn, A.; Kalwa, C. Application of damage mechanics approach for crack propagation in pipeline Werkstoffsimulation Proceedings Article In: 19th Biennial JTM on Pipeline Research, Sidney, Australia, 2013. @inproceedings{Nonn2013e,
title = {Application of damage mechanics approach for crack propagation in pipeline},
author = {A. Nonn and C. Kalwa},
year = {2013},
date = {2013-04-29},
booktitle = {19th Biennial JTM on Pipeline Research},
address = {Sidney, Australia},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
|
Völling, A.; Nonn, A.; Scheider, I. Anwendung des Kohäsivzonenmodells zur Abbildung von duktilem dynamischen Rissfortschritt in Gasfernleitungen Werkstoffsimulation Proceedings Article In: 45. Tagung des AK Bruch, DVM Berichtsband 245, S. 253-262, Berlin, Germany, 2013. @inproceedings{Völling2013,
title = {Anwendung des Kohäsivzonenmodells zur Abbildung von duktilem dynamischen Rissfortschritt in Gasfernleitungen},
author = {A. Völling and A. Nonn and I. Scheider},
year = {2013},
date = {2013-02-19},
booktitle = {45. Tagung des AK Bruch, DVM Berichtsband 245},
pages = {253-262},
address = {Berlin, Germany},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
|
Kofiani, K.; Nonn, A.; Wierzbicki, T. New calibration method for high and low triaxiality and validation on SENT specimens of API X70 Werkstoffsimulation Artikel In: International Journal of Pressure Vessels and Piping, Bd. 111-112, S. 187 - 201, 2013, ISSN: 0308-0161. @article{Kofiani2013b,
title = {New calibration method for high and low triaxiality and validation on SENT specimens of API X70},
author = {K. Kofiani and A. Nonn and T. Wierzbicki},
url = {http://www.sciencedirect.com/science/article/pii/S0308016113001130},
doi = {https://doi.org/10.1016/j.ijpvp.2013.07.004},
issn = {0308-0161},
year = {2013},
date = {2013-01-01},
journal = {International Journal of Pressure Vessels and Piping},
volume = {111-112},
pages = {187 - 201},
abstract = {The determination of the exact mechanical properties of material is essential for an optimal and safe design of linepipes. It is especially important for the prevention of over-engineering and the reliable assessment of complex accidental loading, such as extreme bending due to loss of buoyancy of support, or abrupt ground movement. Currently, the focus of research in offshore deepwater installations and linepipes is towards pre-cracked structures with high triaxiality stress states and complex loading histories. At the same time, low triaxiality stress states must be correctly studied in order to represent shear dominated failure in pipes. A comprehensive experimental and numerical program was undertaken to determine the mechanical properties of the traditional API X70 grade of steel. The material was characterized for anisotropic plasticity, fracture initiation and uncracked ductility for various states of stress. The same material was also used for pre-cracked fracture toughness assessment. The experimental program included flat and round specimens. The first type of tests on flat butterfly-shaped, central hole, notched and circular disk specimens; were selected to address the low stress triaxiality range. Tests on round notched bar specimens and SENT fracture mechanics tests extended the characterization and verification process to higher stress triaxiality values. This program covered a wide range of stress conditions and demonstrated their effect on the material resistance to crack extension. Each test conducted was numerically simulated using solid finite element models, matching the exact geometric and loading history features. The numerical simulation provided information on the local stress and strain fields around the location of the potential or existing cracks. Based on the above hybrid experimental/numerical technique tailored for pipe applications, the MMC fracture model was calibrated. The model relates the material ductility not only to stress triaxiality but also to the Lode parameter. The predictive capabilities of the MMC were then evaluated in the case of SENT testing, used extensively in the pipeline industry. It was shown that the present fracture model calibration can describe fracture behavior of SENT experiments.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The determination of the exact mechanical properties of material is essential for an optimal and safe design of linepipes. It is especially important for the prevention of over-engineering and the reliable assessment of complex accidental loading, such as extreme bending due to loss of buoyancy of support, or abrupt ground movement. Currently, the focus of research in offshore deepwater installations and linepipes is towards pre-cracked structures with high triaxiality stress states and complex loading histories. At the same time, low triaxiality stress states must be correctly studied in order to represent shear dominated failure in pipes. A comprehensive experimental and numerical program was undertaken to determine the mechanical properties of the traditional API X70 grade of steel. The material was characterized for anisotropic plasticity, fracture initiation and uncracked ductility for various states of stress. The same material was also used for pre-cracked fracture toughness assessment. The experimental program included flat and round specimens. The first type of tests on flat butterfly-shaped, central hole, notched and circular disk specimens; were selected to address the low stress triaxiality range. Tests on round notched bar specimens and SENT fracture mechanics tests extended the characterization and verification process to higher stress triaxiality values. This program covered a wide range of stress conditions and demonstrated their effect on the material resistance to crack extension. Each test conducted was numerically simulated using solid finite element models, matching the exact geometric and loading history features. The numerical simulation provided information on the local stress and strain fields around the location of the potential or existing cracks. Based on the above hybrid experimental/numerical technique tailored for pipe applications, the MMC fracture model was calibrated. The model relates the material ductility not only to stress triaxiality but also to the Lode parameter. The predictive capabilities of the MMC were then evaluated in the case of SENT testing, used extensively in the pipeline industry. It was shown that the present fracture model calibration can describe fracture behavior of SENT experiments. |