Strain localization and ductile fracture in advanced high-strength steel sheets

Wen

Fatigue Fract Eng Mat Struct

et al. 2019

The stress state is one of the most notable factors that dominates the initiation of ductile fracture. To examine the effects of the stress state on plasticity and ductile failure, a new tension‐shear specimen that can cover a wide range of stress triaxialities was designed. A fracture locus was constructed in the space of ductility and stress triaxiality for two typical steels based on a series of tests. It is observed that the equivalent plastic strain at failure exhibits a nonmonotonic variation with increasing the value of stress triaxiality. A simple damage model based on the ductility exhaustion concept was used to simulate the failure behaviour, and a good agreement is achieved between simulation results and experimental data. It is further shown that consideration of fracture locus covering a wide range of stress triaxialities is a key to an accurate prediction.

Section: Resultsmentioning

confidence: 99%

Effects of the stress state on plastic deformation and ductile failure: Experiment and numerical simulation using a newly designed tension‐shear specimen

Wen

Fatigue Fract Eng Mat Struct

et al. 2019

“…While the bifurcation analysis has been widely used in the literature, as for instance in Besson et al (2001), Chalal and Abed-Meraim (2015) and Haddag et al (2009) in the context of ductile fracture, the imperfection analysis is less frequently used as a qualitative way of understanding ductile failure. However, some notable studies adopting the imperfection analysis to investigate strain localization are those of Yamamoto (1978), Needleman and Rice (1979), Hutchinson and Tvergaard (1981), Saje et al (1982), Mear and Hutchinson (1985), Nahshon and Hutchinson (2008) and Gruben et al (2017). To trigger localization in a material at reasonable stresses, a softening mechanism must be present in the constitutive equations of the material (Rudnicki and Rice 1975) when the inelastic flow is associative as commonly assumed for metals that are investigated here.…”

Section: Introductionmentioning

confidence: 99%

On the description of ductile fracture in metals by the strain localization theory

2017

Journal of Applied Mechanics

“…While porous plasticity models can be directly used in numerical simulations of structural components to study the structural response, such models also serve as a means to account for material softening in the strain localization analyses. Previous studies using the imperfection band approach have demonstrated its capabilities as a predictive tool in some specific cases [35,36] but have largely been focused on rateindependent material behavior [35][36][37][38]. Strain localization in ratedependent materials was examined by Pan et al [31] and their results display pronounced effects of rate sensitivity on the failure strain.…”

Section: Introductionmentioning

confidence: 99%

A Numerical Study on Ductile Failure of Porous Ductile Solids With Rate-Dependent Matrix Behavior

Dæhli

Morin

Benallal

et al. 2019

This work examines the effects of loading rate on the plastic flow and ductile failure of porous solids exhibiting rate-dependent behavior relevant to many structural metals. Two different modeling approaches for ductile failure are employed and numerical analyses are performed over a wide range of strain rates. Finite element unit cell simulations are carried out to evaluate the macroscopic mechanical response and ductile failure by void coalescence for various macroscopic strain rates. The unit cell results are then used to assess the accuracy of a rate-dependent porous plasticity model, which is subsequently used in strain localization analyses based on the imperfection band approach. Strain localization analyses are conducted for (i) proportional loading paths and (ii) non-proportional loading paths obtained from finite element simulations of axisymmetric and flat tensile specimens. The effects of strain rate are most apparent on the stress–strain response, whereas the effects of strain rate on ductile failure is found to be small for the adopted rate-dependent constitutive model. However, the rate-dependent constitutive formulation tends to regularize the plastic strain field when the strain rate increases. In the unit cell simulations, this slightly increases the strain at coalescence with increasing strain rate compared to a rate-independent constitutive formulation. When the strain rate is sufficiently high, the strain at coalescence becomes constant. The strain localization analyses show a negligible effect of strain rate under proportional loading, while the effect of strain rate is more pronounced when non-proportional loading paths are assigned.