Kramer, S. L. B.; Jones, A.; Mostafa, A.; Ravaji, B.; Tancogne-Dejean, T.; Roth, C. C.; Gorji, M.; Pack, K.; Foster, J. T.; Behzadinasab, M.; Sobotka, J. C.; McFarland, J. M.; Stein, J.; Spear, A. D.; Newell, P.; Czabaj, M. W.; Williams, B.; Simha, H.; Gesing, M.; Gilkey, L. N.; Jones, C. A.; Dingreville, R.; Sanborn, S. E.; Bignell, J. L.; Cerrone, A. R.; Keim, V.; Nonn, A.; Cooreman, S.; Thibaux, P.; Ames, N.; Connor, D. O.; Parno, M.; Davis, B.; Tucker, J.; Coudrillier, B.; Karlson, K. N.; Ostien, J. T.; Foulk, J. W.; Hammetter, C. I.; Grange, S.; Emery, J. M.; Brown, J. A.; Bishop, J. E.; Johnson, K. L.; Ford, K. R.; Brinckmann, S.; Neilsen, M. K.; Jackiewicz, J.; Ravi-Chandar, K.; Ivanoff, T.; Salzbrenner, B. C.; Boyce, B. L. The third Sandia fracture challenge: predictions of ductile fracture in additively manufactured metal Werkstoffsimulation Artikel In: International Journal of Fracture, 218 (1), S. 5-61, 2019, ISSN: 1573-2673. @article{Kramer2019,
title = {The third Sandia fracture challenge: predictions of ductile fracture in additively manufactured metal},
author = {S. L. B. Kramer and A. Jones and A. Mostafa and B. Ravaji and T. Tancogne-Dejean and C. C. Roth and M. Gorji and K. Pack and J. T. Foster and M. Behzadinasab and J. C. Sobotka and J. M. McFarland and J. Stein and A. D. Spear and P. Newell and M. W. Czabaj and B. Williams and H. Simha and M. Gesing and L. N. Gilkey and C. A. Jones and R. Dingreville and S. E. Sanborn and J. L. Bignell and A. R. Cerrone and V. Keim and A. Nonn and S. Cooreman and P. Thibaux and N. Ames and D. O. Connor and M. Parno and B. Davis and J. Tucker and B. Coudrillier and K. N. Karlson and J. T. Ostien and J. W. Foulk and C. I. Hammetter and S. Grange and J. M. Emery and J. A. Brown and J. E. Bishop and K. L. Johnson and K. R. Ford and S. Brinckmann and M. K. Neilsen and J. Jackiewicz and K. Ravi-Chandar and T. Ivanoff and B. C. Salzbrenner and B. L. Boyce},
doi = {10.1007/s10704-019-00361-1},
issn = {1573-2673},
year = {2019},
date = {2019-01-01},
journal = {International Journal of Fracture},
volume = {218},
number = {1},
pages = {5-61},
abstract = {The Sandia Fracture Challenges provide a forum for the mechanics community to assess its ability to predict ductile fracture through a blind, round-robin format where mechanicians are challenged to predict the deformation and failure of an arbitrary geometry given experimental calibration data. The Third Challenge (SFC3) required participants to predict fracture in an additively manufactured (AM) 316L stainless steel bar containing through holes and internal cavities that could not have been conventionally machined. The volunteer participants were provided extensive data including tension and notched tensions tests of 316L specimens built on the same build-plate as the Challenge geometry, micro-CT scans of the Challenge specimens and geometric measurements of the feature based on the scans, electron backscatter diffraction (EBSD) information on grain texture, and post-test fractography of the calibration specimens. Surprisingly, the global behavior of the SFC3 geometry specimens had modest variability despite being made of AM metal, with all of the SFC3 geometry specimens failing under the same failure mode. This is attributed to the large stress concentrations from the holes overwhelming the stochastic local influence of the AM voids and surface roughness. The teams were asked to predict a number of quantities of interest in the response based on global and local measures that were compared to experimental data, based partly on Digital Image Correlation (DIC) measurements of surface displacements and strains, including predictions of variability in the resulting fracture response, as the basis for assessment of the predictive capabilities of the modeling and simulation strategies. Twenty-one teams submitted predictions obtained from a variety of methods: the finite element method (FEM) or the mesh-free, peridynamic method; solvers with explicit time integration, implicit time integration, or quasi-statics; fracture methods including element deletion, peridynamics with bond damage, XFEM, damage (stiffness degradation), and adaptive remeshing. These predictions utilized many different material models: plasticity models including J2 plasticity or Hill yield with isotropic hardening, mixed Swift-Voce hardening, kinematic hardening, or custom hardening curves; fracture criteria including GTN model, Hosford-Coulomb, triaxiality-dependent strain, critical fracture energy, damage-based model, critical void volume fraction, and Johnson-Cook model; and damage evolution models including damage accumulation and evolution, crack band model, fracture energy, displacement value threshold, incremental stress triaxiality, Cocks-Ashby void growth, and void nucleation, growth, and coalescence. Teams used various combinations of calibration data from tensile specimens, the notched tensile specimens, and literature data. A detailed comparison of results based of these different methods is presented in this paper to suggest a set of best practices for modeling ductile fracture in situations like the SFC3 AM-material problem. All blind predictions identified the nominal crack path and initiation location correctly. The SFC3 participants generally fared better in their global predictions of deformation and failure than the participants in the previous Challenges, suggesting the relative maturity of the models used and adoption of best practices from previous Challenges. This paper provides detailed analyses of the results, including discussion of the utility of the provided data, challenges of the experimental-numerical comparison, defects in the AM material, and human factors.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The Sandia Fracture Challenges provide a forum for the mechanics community to assess its ability to predict ductile fracture through a blind, round-robin format where mechanicians are challenged to predict the deformation and failure of an arbitrary geometry given experimental calibration data. The Third Challenge (SFC3) required participants to predict fracture in an additively manufactured (AM) 316L stainless steel bar containing through holes and internal cavities that could not have been conventionally machined. The volunteer participants were provided extensive data including tension and notched tensions tests of 316L specimens built on the same build-plate as the Challenge geometry, micro-CT scans of the Challenge specimens and geometric measurements of the feature based on the scans, electron backscatter diffraction (EBSD) information on grain texture, and post-test fractography of the calibration specimens. Surprisingly, the global behavior of the SFC3 geometry specimens had modest variability despite being made of AM metal, with all of the SFC3 geometry specimens failing under the same failure mode. This is attributed to the large stress concentrations from the holes overwhelming the stochastic local influence of the AM voids and surface roughness. The teams were asked to predict a number of quantities of interest in the response based on global and local measures that were compared to experimental data, based partly on Digital Image Correlation (DIC) measurements of surface displacements and strains, including predictions of variability in the resulting fracture response, as the basis for assessment of the predictive capabilities of the modeling and simulation strategies. Twenty-one teams submitted predictions obtained from a variety of methods: the finite element method (FEM) or the mesh-free, peridynamic method; solvers with explicit time integration, implicit time integration, or quasi-statics; fracture methods including element deletion, peridynamics with bond damage, XFEM, damage (stiffness degradation), and adaptive remeshing. These predictions utilized many different material models: plasticity models including J2 plasticity or Hill yield with isotropic hardening, mixed Swift-Voce hardening, kinematic hardening, or custom hardening curves; fracture criteria including GTN model, Hosford-Coulomb, triaxiality-dependent strain, critical fracture energy, damage-based model, critical void volume fraction, and Johnson-Cook model; and damage evolution models including damage accumulation and evolution, crack band model, fracture energy, displacement value threshold, incremental stress triaxiality, Cocks-Ashby void growth, and void nucleation, growth, and coalescence. Teams used various combinations of calibration data from tensile specimens, the notched tensile specimens, and literature data. A detailed comparison of results based of these different methods is presented in this paper to suggest a set of best practices for modeling ductile fracture in situations like the SFC3 AM-material problem. All blind predictions identified the nominal crack path and initiation location correctly. The SFC3 participants generally fared better in their global predictions of deformation and failure than the participants in the previous Challenges, suggesting the relative maturity of the models used and adoption of best practices from previous Challenges. This paper provides detailed analyses of the results, including discussion of the utility of the provided data, challenges of the experimental-numerical comparison, defects in the AM material, and human factors. |
Keim, V.; Cerrone, A.; Nonn, A. Using local damage models to predict fracture in additively manufactured specimens Werkstoffsimulation Artikel In: International Journal of Fracture, 218 (1), S. 135-147, 2019, ISSN: 1573-2673. @article{Keim2019b,
title = {Using local damage models to predict fracture in additively manufactured specimens},
author = {V. Keim and A. Cerrone and A. Nonn},
doi = {10.1007/s10704-019-00371-z},
issn = {1573-2673},
year = {2019},
date = {2019-01-01},
journal = {International Journal of Fracture},
volume = {218},
number = {1},
pages = {135-147},
abstract = {This paper explores the efficacy of employing local damage models, normally applied to ductile material systems manufactured by subtractive techniques, to additively manufactured laboratory specimens. While these specimens were ductile and metallic, their additive character (i.e. porosity and surface roughness) could have had potential to activate multiple life-limiting failure paths, thus obfuscating failure prediction. Herein, two damage models are considered and compared: the micromechanical Gurson-Tvergaard-Needleman model and a Crack Band model of the strain-based, phenomenological genre. Simulations used to calibrate elastic and plastic material properties and predict damage in a novel, non-standard specimen were quasi-static, explicit. Both damage models proved capable in resolving the experimentally-observed failure path and associated loading conditions. The analyses described herein were made as part of the Third Sandia Fracture Challenge.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This paper explores the efficacy of employing local damage models, normally applied to ductile material systems manufactured by subtractive techniques, to additively manufactured laboratory specimens. While these specimens were ductile and metallic, their additive character (i.e. porosity and surface roughness) could have had potential to activate multiple life-limiting failure paths, thus obfuscating failure prediction. Herein, two damage models are considered and compared: the micromechanical Gurson-Tvergaard-Needleman model and a Crack Band model of the strain-based, phenomenological genre. Simulations used to calibrate elastic and plastic material properties and predict damage in a novel, non-standard specimen were quasi-static, explicit. Both damage models proved capable in resolving the experimentally-observed failure path and associated loading conditions. The analyses described herein were made as part of the Third Sandia Fracture Challenge. |
Nonn, A.; Paredes, M.; Keim, V.; Wierzbicki, T. Comparison of Fracture Models to Quantify the Effects of Material Plasticity on the Ductile Fracture Propagation in Pipelines Werkstoffsimulation Konferenzbeitrag In: Proceedings of the 2018 12th International Pipeline Conference, Volume 3: Operations, Monitoring, and Maintenance, Materials and Joining, Calgary, Alberta, Canada, 2018, ISBN: 978-0-7918-5188-3. @inproceedings{Nonn2018,
title = {Comparison of Fracture Models to Quantify the Effects of Material Plasticity on the Ductile Fracture Propagation in Pipelines},
author = {A. Nonn and M. Paredes and V. Keim and T. Wierzbicki},
doi = {10.1115/IPC2018-78366},
isbn = {978-0-7918-5188-3},
year = {2018},
date = {2018-09-24},
booktitle = {Proceedings of the 2018 12th International Pipeline Conference, Volume 3: Operations, Monitoring, and Maintenance, Materials and Joining},
address = {Calgary, Alberta, Canada},
series = {International Pipeline Conference},
abstract = {Various numerical approaches have been developed in the last years aimed to simulate the ductile fracture propagation in pipelines transporting CO2 or natural gas. However, a reliable quantification of the influence of material plasticity on the fracture resistance is still missing. Therefore, more accurate description of the material plasticity on the ductile fracture propagation is required based on a suitable numerical methodology.In this study, different plasticity and fracture models are compared regarding the ductile fracture propagation in X100 pipeline steel with the objective to quantify the influence of plasticity parameters on the fracture resistance. The plastic behavior of the investigated material is considered by the quadratic yield surface in conjunction with a non-associated quadratic plastic flow potential. The strain hardening can be appropriately described by the mixed Swift-Voce law. The simulations of ductile fracture are conducted by an uncoupled, modified Mohr-Coulomb (MMC) and the micromechanically based Gurson-Tvergaard-Needleman (GTN) models. In contract to the original GTN model, the MMC model is capable of describing ductile failure over wide range of stress states. Thus, ductile fracture resistance can be estimated for various load and fracture scenarios. Both models are used for the simulation of fracture propagation in DWTT and 3D pressurized pipe sections. The results from the present work can serve as a basis for establishing the correlation between plasticity parameters and ductile fracture propagation.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Various numerical approaches have been developed in the last years aimed to simulate the ductile fracture propagation in pipelines transporting CO2 or natural gas. However, a reliable quantification of the influence of material plasticity on the fracture resistance is still missing. Therefore, more accurate description of the material plasticity on the ductile fracture propagation is required based on a suitable numerical methodology.In this study, different plasticity and fracture models are compared regarding the ductile fracture propagation in X100 pipeline steel with the objective to quantify the influence of plasticity parameters on the fracture resistance. The plastic behavior of the investigated material is considered by the quadratic yield surface in conjunction with a non-associated quadratic plastic flow potential. The strain hardening can be appropriately described by the mixed Swift-Voce law. The simulations of ductile fracture are conducted by an uncoupled, modified Mohr-Coulomb (MMC) and the micromechanically based Gurson-Tvergaard-Needleman (GTN) models. In contract to the original GTN model, the MMC model is capable of describing ductile failure over wide range of stress states. Thus, ductile fracture resistance can be estimated for various load and fracture scenarios. Both models are used for the simulation of fracture propagation in DWTT and 3D pressurized pipe sections. The results from the present work can serve as a basis for establishing the correlation between plasticity parameters and ductile fracture propagation. |
Paredes, M.; Keim, V.; Nonn, A.; Wierzbicki, T. Effect of plasticity parameter on the crack propagation in steel pipelines Werkstoffsimulation Konferenzbeitrag In: Proceedings of the conference on Technology for future and ageing piplines, Ghent, Belgium, 2018. @inproceedings{Paredes2018,
title = {Effect of plasticity parameter on the crack propagation in steel pipelines},
author = {M. Paredes and V. Keim and A. Nonn and T. Wierzbicki},
year = {2018},
date = {2018-04-01},
booktitle = {Proceedings of the conference on Technology for future and ageing piplines},
address = {Ghent, Belgium},
abstract = {A reliable characterization of material fracture resistance and derivation of ductile-fracture-arrest criteria for modern linepipe steels belong to major challenges within the current pipeline research. Although many efforts have been undertaken to meet these challenges, there are still open issues related to the understanding and quantification of the material properties on unstable ductile fracture propagation. There is a general consensus that the fracture velocity is controlled by the speed of travelling plastic hinge (propagating neck or plastic instability/collapse) due to axial through-wall thinning in front of the fracture. To account for the effect of material ductility on fracture propagation resistance, a plasticity parameter, the yield-to-tensile ratio, has been recently implemented in the Battelle fracture velocity model. The improved results from this modification indicate that an accurate prediction of crack propagation and arrest require a comprehensive characterization and consideration of material plasticity and fracture.
Therefore, this paper aims to study and quantify the influence of plasticity (characteristic stress/strain values, strain hardening, plastic anisotropy) parameters on dynamic crack propagation in the X100 steel pipelines. Plastic anisotropy is described by Hill’48 quadratic yield function along with a non-associated flow rule which allows to incorporate the effect of a different directionality of the r-values from the yield stress ratios without losing advantages of quadratic functions. The strain hardening is captured by a linear combination of Swift power law and Voce exponential law. The ductile fracture propagation is simulated by Modified-Mohr-Coulomb (MMC) fracture model which includes a joint effect of stress triaxiality, Lode angle and is applicable to problems with changing loading history. The model parameters are verified based on results from single-edge-notched (SENT) and drop-weight-tear-test (DWTT) tests. The influence of plasticity parameters on the fracture propagation is examined and quantified using 3D pressurized pipe models. The results will provide valuable insights on key plasticity parameters affecting fracture resistance and thus serve as a basis for more accurate assessment of deformation/fracture process of the modern pipeline steels.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
A reliable characterization of material fracture resistance and derivation of ductile-fracture-arrest criteria for modern linepipe steels belong to major challenges within the current pipeline research. Although many efforts have been undertaken to meet these challenges, there are still open issues related to the understanding and quantification of the material properties on unstable ductile fracture propagation. There is a general consensus that the fracture velocity is controlled by the speed of travelling plastic hinge (propagating neck or plastic instability/collapse) due to axial through-wall thinning in front of the fracture. To account for the effect of material ductility on fracture propagation resistance, a plasticity parameter, the yield-to-tensile ratio, has been recently implemented in the Battelle fracture velocity model. The improved results from this modification indicate that an accurate prediction of crack propagation and arrest require a comprehensive characterization and consideration of material plasticity and fracture.
Therefore, this paper aims to study and quantify the influence of plasticity (characteristic stress/strain values, strain hardening, plastic anisotropy) parameters on dynamic crack propagation in the X100 steel pipelines. Plastic anisotropy is described by Hill’48 quadratic yield function along with a non-associated flow rule which allows to incorporate the effect of a different directionality of the r-values from the yield stress ratios without losing advantages of quadratic functions. The strain hardening is captured by a linear combination of Swift power law and Voce exponential law. The ductile fracture propagation is simulated by Modified-Mohr-Coulomb (MMC) fracture model which includes a joint effect of stress triaxiality, Lode angle and is applicable to problems with changing loading history. The model parameters are verified based on results from single-edge-notched (SENT) and drop-weight-tear-test (DWTT) tests. The influence of plasticity parameters on the fracture propagation is examined and quantified using 3D pressurized pipe models. The results will provide valuable insights on key plasticity parameters affecting fracture resistance and thus serve as a basis for more accurate assessment of deformation/fracture process of the modern pipeline steels. |
Keim, V.; Nonn, A.; Lenz, D.; Brinnel, V.; Münstermann, S. Simulation of the ductile fracture behaviour of high toughness pipeline steels using combined damage models Werkstoffsimulation Konferenzbeitrag In: Proceedings of the conference on Technology for future and ageing piplines, Ghent, Belgium, 2018. @inproceedings{Keim2018,
title = {Simulation of the ductile fracture behaviour of high toughness pipeline steels using combined damage models},
author = {V. Keim and A. Nonn and D. Lenz and V. Brinnel and S. Münstermann},
year = {2018},
date = {2018-01-01},
booktitle = {Proceedings of the conference on Technology for future and ageing piplines},
address = {Ghent, Belgium},
abstract = {The complex mechanical and corrosive loads of modern pipeline systems transporting oil, natural gas and CO2 impose steadily increasing requirements on material properties. The majority of current design standards still limit the application of modern high toughness linepipe steels due to the specification of material requirements in terms of energy levels from Charpy impact or Drop-Weight-Tear tests (DWTT). Furthermore, abnormal fracture appearance (AFA), abnormal fracture behavior (AFB) and separations question the correlation between laboratory tests and components’ fracture behavior. In consequence, research activities have been conducted recently aiming at developing modified or novel experimental methods for the characterization of ductile-to-brittle fracture behavior. To quantify the effects of various parameters on fracture behavior and derive suitable correlations, it is necessary to accompany these activities by numerical simulations with appropriate damage models for ductile and cleavage fracture. In this paper, a coupled, phenomenological damage model for ductile fracture is applied to study the structural behavior of pipelines due to its pronounced computational efficiency, which is combined with a cleavage fracture model in later phases of the project. The parameters for the model are determined by small scale tests with various multi-axial loading conditions. The validated damage model was successfully used to simulate the fracture behavior DWTT specimens. Finally, these models allow for the investigation of material, geometry and loading effects on fracture and crack arrest behavior of pipes in transition region.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
The complex mechanical and corrosive loads of modern pipeline systems transporting oil, natural gas and CO2 impose steadily increasing requirements on material properties. The majority of current design standards still limit the application of modern high toughness linepipe steels due to the specification of material requirements in terms of energy levels from Charpy impact or Drop-Weight-Tear tests (DWTT). Furthermore, abnormal fracture appearance (AFA), abnormal fracture behavior (AFB) and separations question the correlation between laboratory tests and components’ fracture behavior. In consequence, research activities have been conducted recently aiming at developing modified or novel experimental methods for the characterization of ductile-to-brittle fracture behavior. To quantify the effects of various parameters on fracture behavior and derive suitable correlations, it is necessary to accompany these activities by numerical simulations with appropriate damage models for ductile and cleavage fracture. In this paper, a coupled, phenomenological damage model for ductile fracture is applied to study the structural behavior of pipelines due to its pronounced computational efficiency, which is combined with a cleavage fracture model in later phases of the project. The parameters for the model are determined by small scale tests with various multi-axial loading conditions. The validated damage model was successfully used to simulate the fracture behavior DWTT specimens. Finally, these models allow for the investigation of material, geometry and loading effects on fracture and crack arrest behavior of pipes in transition region. |
