Ductile fracture of Q460 steel: Effects of stress triaxiality and Lode angle

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: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

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

Numerical Meth Engineering

“…The specific idea is to modify the dependency on the plastic multiplier to differentiate the accumulation through cycles. A Lode angle dependency is also needed, as proved by Xue and confirmed recently by Li et al…”

Section: Resultsmentioning

confidence: 72%

A return mapping algorithm for elastoplastic and ductile damage constitutive equations using the subloading surface method

Fincato

Tsutsumi

2017

In this paper is presented a return mapping algorithm for an elastoplastic/damage model that couples the constitutive equations of an unconventional plasticity model with the phenomenological description of ductile damage in the continuum damage mechanics framework. This approach combines the advantages of describing the mechanical property degradation by using the Lemaitre model with the realistic accumulation of plastic deformation in cyclic mobility problems from the subloading surface model. Most of the damage models for ductile failure focus on monotonic loading conditions, whereas the present model aims to extend the investigation to cyclic loading and low‐cycle fatigue problems. A cutting‐plane algorithm is adopted to describe the material behavior that considers both isotropic and kinematic hardening laws. Two simple numerical studies show that the elastoplastic and damage model is implemented correctly, displaying a quadratic rate of convergence for local equilibria and precise solutions, even for large‐prescribed strain increments.

QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY

“…conventional approach: Xue 10), 14) , Bao and Wierzbicki 9) , Wierzbicki et al 11) , Papasidero et al 16) , Cortese et al 17) ), it reduces its influence following the generation of plastic deformations. A future experimental campaign is however necessary to better characterize the Lode angle dependence of steels.…”

Section: Resultsmentioning

confidence: 99%

“…The work presented in this paper aims to test the Lode angle dependency of a Q460 steel reproducing the experimental and numerical results obtained in 11) . The material parameters for subloading surface are reported in Table 1.…”

Section: Numerical Simulationsmentioning

confidence: 99%

Effect of the stress triaxiality and Lode angle on the ductile damage evolution

Fincato

Tsutsumi

2017

Damage in a structure is caused by material degradation due to initiation, growth and coalescence of micro-cracks/voids. In the recent years this topic acquired great importance in order to obtain a better design and to prevent the failure of components and structures. The present work aims to consider the influence of the stress triaxiality and the Lode angle effect on the ductile damage evolution, since it has been experimentally proved that the loading conditions highly affect the effective strain (i.e. cumulative plastic strain at failure). An ad hoc Lode angle function is adopted, together with the ductile damage evolution law proposed by Lemaitre, associating the decrease of the Lode angle influence with the generation of large plastic strain. On the other hands the choice of coupling the continuum damage mechanics framework together with an unconventional plasticity model is functional to investigate cyclic loading problems, since conventional plastic algorithms tend to overestimate the material ratcheting, leading to a wrong accumulation of the damage through cycles.