The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Dirk Mohr - One of the best experts on this subject based on the ideXlab platform.
-
stress state and strain rate dependent ductile fracture of dual and complex phase steel
Mechanics of Materials, 2018Co-Authors: Borja Erice, Christian C Roth, Dirk MohrAbstract:Abstract A comprehensive combined hybrid numerical-experimental program is executed on three advanced high strength steels (DP980, CP980 and CP1180) with the objective of validating (1) the hypothesis of a positive strain rate effect on the ductility under biaxial tension, as well as (2) the Hosford–Coulomb Model assumptions with regards to the Lode parameter and stress triaxiality dependency of fracture initiation. The basic low strain rate testing program included punch, notched tension, central hole tension and smiley shear experiments. In addition, intermediate and high strain rate SHPB experiments are carried out to characterize the effect of strain rate. A non-associated quadratic plasticity Model with Swift-Voce hardening and Johnson–Cook type of strain rate and temperature dependency is employed to Model the large deformation response. The fracture Model parameters are identified based on the loading paths to fracture extracted from numerical simulations with fine solid element meshes up to the point of fracture initiation in the experiments. It is found that the simple three-parameter Hosford–Coulomb Model can describe the pronounced stress state effect on the strain to fracture for all materials. The results for notched tension also confirm that the ductility increases as function of the loading velocity for biaxial loading.
-
a rate dependent hosford Coulomb Model for predicting ductile fracture at high strain rates
European Physical Journal Web of Conferences, 2015Co-Authors: Stephane J Marcadet, Borja Erice, Christian C Roth, Dirk MohrAbstract:The Hosford-Coulomb Model incorporates the important effect of the Lode angle parameter in addition to the stress triaxiality to predict the initiation of ductile fracture. A strain-rate dependent extension of the Hosford-Coulomb Model is presented to describe the results from low, intermediate and high strain rate fracture experiments on advanced high strength steels (DP590 and TRIP780). The Model predictions agree well with the experimental observation of an increase in ductility as function of strain rate for stress states ranging from uniaxial to equi-biaxial tension.
-
micromechanically motivated phenomenological hosford Coulomb Model for predicting ductile fracture initiation at low stress triaxialities
International Journal of Solids and Structures, 2015Co-Authors: Dirk Mohr, Stephane J MarcadetAbstract:Abstract A phenomenological ductile fracture initiation Model for metals is developed for predicting ductile fracture in industrial practice. Its formulation is based on the assumption that the onset of fracture is imminent with the formation of a primary or secondary band of localization. The results from a unit cell analysis on a Levy–von Mises material with spherical defects revealed that a Mohr–Coulomb type of Model is suitable for predicting the onset of shear and normal localization. To improve the agreement of the Model predictions with experimental results, an extended Mohr–Coulomb criterion is proposed which makes use of the Hosford equivalent stress in combination with the normal stress acting on the plane of maximum shear. A fracture initiation Model is obtained by transforming the localization criterion from stress space to the space of equivalent plastic strain, stress triaxiality and Lode angle parameter using the material’s isotropic hardening law. Experimental results are presented for three different advanced high strength steels. For each material, the onset of fracture is characterized for five distinct stress states including butterfly shear, notched tension, tension with a central hole and punch experiments. The comparison of Model predictions with the experimental results demonstrates that the proposed Hosford–Coulomb Model can predict the instant of ductile fracture initiation in advanced high strength steels with good accuracy.
-
predicting ductile fracture of low carbon steel sheets stress based versus mixed stress strain based mohr Coulomb Model
International Journal of Solids and Structures, 2013Co-Authors: Fabien Ebnoether, Dirk MohrAbstract:Abstract Two distinct implementations of the Mohr–Coulomb failure Model are used in conjunction with a non-associated quadratic plasticity Model to describe the onset of fracture in low carbon steel sheets. The stress-based version corresponds to the original Mohr–Coulomb Model in stress space. For the mixed stress/strain-based version, the Mohr–Coulomb failure criterion is first transformed into the space of stress triaxiality, Lode angle parameter and equivalent plastic strain and then used as stress-state dependent weighting function in a damage indicator Model. Basic fracture experiments including tensile specimens of different notch radii and a punch test are performed to calibrate the material parameters of the respective Models. Subsequently, the Models are used to predict the crack initiation in a Hasek test and during the stamping of an anticlastic structure. Unlike for the calibration experiments, the loading history during stamping is highly non-linear. Both Models can be calibrated with similar accuracy, but the strain-based Model predicts the instant of onset of fracture with greater accuracy in the stamping experiment which is an advantage of the empirical damage accumulation rule.
Stephane J Marcadet - One of the best experts on this subject based on the ideXlab platform.
-
a rate dependent hosford Coulomb Model for predicting ductile fracture at high strain rates
European Physical Journal Web of Conferences, 2015Co-Authors: Stephane J Marcadet, Borja Erice, Christian C Roth, Dirk MohrAbstract:The Hosford-Coulomb Model incorporates the important effect of the Lode angle parameter in addition to the stress triaxiality to predict the initiation of ductile fracture. A strain-rate dependent extension of the Hosford-Coulomb Model is presented to describe the results from low, intermediate and high strain rate fracture experiments on advanced high strength steels (DP590 and TRIP780). The Model predictions agree well with the experimental observation of an increase in ductility as function of strain rate for stress states ranging from uniaxial to equi-biaxial tension.
-
micromechanically motivated phenomenological hosford Coulomb Model for predicting ductile fracture initiation at low stress triaxialities
International Journal of Solids and Structures, 2015Co-Authors: Dirk Mohr, Stephane J MarcadetAbstract:Abstract A phenomenological ductile fracture initiation Model for metals is developed for predicting ductile fracture in industrial practice. Its formulation is based on the assumption that the onset of fracture is imminent with the formation of a primary or secondary band of localization. The results from a unit cell analysis on a Levy–von Mises material with spherical defects revealed that a Mohr–Coulomb type of Model is suitable for predicting the onset of shear and normal localization. To improve the agreement of the Model predictions with experimental results, an extended Mohr–Coulomb criterion is proposed which makes use of the Hosford equivalent stress in combination with the normal stress acting on the plane of maximum shear. A fracture initiation Model is obtained by transforming the localization criterion from stress space to the space of equivalent plastic strain, stress triaxiality and Lode angle parameter using the material’s isotropic hardening law. Experimental results are presented for three different advanced high strength steels. For each material, the onset of fracture is characterized for five distinct stress states including butterfly shear, notched tension, tension with a central hole and punch experiments. The comparison of Model predictions with the experimental results demonstrates that the proposed Hosford–Coulomb Model can predict the instant of ductile fracture initiation in advanced high strength steels with good accuracy.
Borja Erice - One of the best experts on this subject based on the ideXlab platform.
-
stress state and strain rate dependent ductile fracture of dual and complex phase steel
Mechanics of Materials, 2018Co-Authors: Borja Erice, Christian C Roth, Dirk MohrAbstract:Abstract A comprehensive combined hybrid numerical-experimental program is executed on three advanced high strength steels (DP980, CP980 and CP1180) with the objective of validating (1) the hypothesis of a positive strain rate effect on the ductility under biaxial tension, as well as (2) the Hosford–Coulomb Model assumptions with regards to the Lode parameter and stress triaxiality dependency of fracture initiation. The basic low strain rate testing program included punch, notched tension, central hole tension and smiley shear experiments. In addition, intermediate and high strain rate SHPB experiments are carried out to characterize the effect of strain rate. A non-associated quadratic plasticity Model with Swift-Voce hardening and Johnson–Cook type of strain rate and temperature dependency is employed to Model the large deformation response. The fracture Model parameters are identified based on the loading paths to fracture extracted from numerical simulations with fine solid element meshes up to the point of fracture initiation in the experiments. It is found that the simple three-parameter Hosford–Coulomb Model can describe the pronounced stress state effect on the strain to fracture for all materials. The results for notched tension also confirm that the ductility increases as function of the loading velocity for biaxial loading.
-
a rate dependent hosford Coulomb Model for predicting ductile fracture at high strain rates
European Physical Journal Web of Conferences, 2015Co-Authors: Stephane J Marcadet, Borja Erice, Christian C Roth, Dirk MohrAbstract:The Hosford-Coulomb Model incorporates the important effect of the Lode angle parameter in addition to the stress triaxiality to predict the initiation of ductile fracture. A strain-rate dependent extension of the Hosford-Coulomb Model is presented to describe the results from low, intermediate and high strain rate fracture experiments on advanced high strength steels (DP590 and TRIP780). The Model predictions agree well with the experimental observation of an increase in ductility as function of strain rate for stress states ranging from uniaxial to equi-biaxial tension.
Christian C Roth - One of the best experts on this subject based on the ideXlab platform.
-
stress state and strain rate dependent ductile fracture of dual and complex phase steel
Mechanics of Materials, 2018Co-Authors: Borja Erice, Christian C Roth, Dirk MohrAbstract:Abstract A comprehensive combined hybrid numerical-experimental program is executed on three advanced high strength steels (DP980, CP980 and CP1180) with the objective of validating (1) the hypothesis of a positive strain rate effect on the ductility under biaxial tension, as well as (2) the Hosford–Coulomb Model assumptions with regards to the Lode parameter and stress triaxiality dependency of fracture initiation. The basic low strain rate testing program included punch, notched tension, central hole tension and smiley shear experiments. In addition, intermediate and high strain rate SHPB experiments are carried out to characterize the effect of strain rate. A non-associated quadratic plasticity Model with Swift-Voce hardening and Johnson–Cook type of strain rate and temperature dependency is employed to Model the large deformation response. The fracture Model parameters are identified based on the loading paths to fracture extracted from numerical simulations with fine solid element meshes up to the point of fracture initiation in the experiments. It is found that the simple three-parameter Hosford–Coulomb Model can describe the pronounced stress state effect on the strain to fracture for all materials. The results for notched tension also confirm that the ductility increases as function of the loading velocity for biaxial loading.
-
a rate dependent hosford Coulomb Model for predicting ductile fracture at high strain rates
European Physical Journal Web of Conferences, 2015Co-Authors: Stephane J Marcadet, Borja Erice, Christian C Roth, Dirk MohrAbstract:The Hosford-Coulomb Model incorporates the important effect of the Lode angle parameter in addition to the stress triaxiality to predict the initiation of ductile fracture. A strain-rate dependent extension of the Hosford-Coulomb Model is presented to describe the results from low, intermediate and high strain rate fracture experiments on advanced high strength steels (DP590 and TRIP780). The Model predictions agree well with the experimental observation of an increase in ductility as function of strain rate for stress states ranging from uniaxial to equi-biaxial tension.
I L Iosilevskiy - One of the best experts on this subject based on the ideXlab platform.
-
features of non congruent phase transition in modified Coulomb Model of the binary ionic mixture
Journal of Physics: Conference Series, 2016Co-Authors: N E Stroev, I L IosilevskiyAbstract:Non-congruent gas-liquid phase transition (NCPT) have been studied previously in modified Coulomb Model of a binary ionic mixture C(+6) + O(+8) on a uniformly compressible ideal electronic background /BIM(~)/. The features of NCPT in improved version of the BIM(~) Model for the same mixture on background of non-ideal electronic Fermi-gas and comparison it with the previous calculations are the subject of present study. Analytical fits for Coulomb corrections to equation of state of electronic and ionic subsystems were used in present calculations within the Gibbs-Guggenheim conditions of non-congruent phase equilibrium. Parameters of critical point-line were calculated on the entire range of proportions of mixed ions 0 < X < 1. Strong "distillation" effect was found for NCPT in the present BIM(~) Model. Just similar distillation was obtained in the variant of NCPT in dense nuslear matter. The absence of azeotropic compositions was revealed in studied variants of BIM(~) in contrast to an explicit existence of the azeotropic compositions for the NCPT in chemically reacting plasmas and in astrophysical applications.
-
features of non congruent phase transition in modified Coulomb Model of the binary ionic mixture
arXiv: Plasma Physics, 2016Co-Authors: N E Stroev, I L IosilevskiyAbstract:Non-congruent gas-liquid phase transition (NCPT) have been studied in modified Coulomb Model of a binary ionic mixture C(+6) + O(+8) on a \textit{uniformly compressible} ideal electronic background /BIM($\sim$)/. The features of NCPT in improved version of the BIM($\sim$) Model for the same mixture on background of \textit{non-ideal} electronic Fermi-gas and comparison it with the previous calculations are the subject of present study. Analytical fits for Coulomb corrections to EoS of electronic and ionic subsystems were used in present calculations within the Gibbs--Guggenheim conditions of non-congruent phase equilibrium.Parameters of critical point-line (CPL) were calculated on the entire range of proportions of mixed ions $0
