Critical hardening rate model for predicting path-dependent ductile fracture

Abstract

A new phenomenological framework for predicting ductile fracture after non-proportional loading paths is proposed, implemented into FE software and validated experimentally for a limited set of monotonic and reverse loading conditions. Assuming that ductile fracture initiation is imminent with the formation of a shear band, a shear localization criterion in terms of the elastoplastic tangent matrix is sufficient from a theoretical point of view to predict ductile fracture after proportional and non-proportional loading. As a computationally efficient alternative to analyzing the acoustic tensor, a phenomenological criterion is proposed which expresses the equivalent hardening rate at the onset of fracture as a function of the stress triaxiality and the Lode angle parameter. The mathematical form of the criterion is chosen such that it reduces to the Hosford-Coulomb criterion for proportional loading. The proposed framework implies that the plasticity model is responsible for the effect of loading history on ductile fracture. Important non-isotropic hardening features such as the Bauschinger effect, transient softening and hardening stagnation must be taken into account by the plasticity model formulation to obtain reasonable fracture predictions after nonproportional loading histories. A new comprehensive plasticity model taking the above effects into account is thus an important byproduct of this work. In addition, compression-tension and reverse-shear experiments are performed on specimens extracted from dualphase steel sheets to validate the proposed plasticity and fracture model.

Experimental fracture characterisation of an anisotropic magnesium alloy sheet in proportional and non-proportional loading conditions

“…Linear damage in Eq. ( 16) was first utilized by Johnson and Cook (1985) and is also identical to definition of the so-called "damage indicator" utilized in Marcadet and Mohr (2016). Eqs.…”

Identification of Chaboche–Lemaitre combined isotropic–kinematic hardening model parameters assisted by the fuzzy logic analysis

“…The evolution of isotropic hardening dr( p) is determined by the Voce isotropic law defined as (Eq. (9)) [45]:…”

Extension of the modified Bai‐Wierzbicki model for predicting ductile fracture under complex loading conditions

“…Berto et al 26 applied an energy-based approach to simulate the damage behaviour of a notched specimen under torsion loading. Recent studies [27][28][29] have suggested that not only the damage evolution law but also an accurate plasticity description is important for modelling damage behaviour in complex loadings. Depending on the application, the advanced plasticity model may have to consider the stress state, anisotropy, and kinematic hardening to accurately describe the stress-strain behaviour of material under complex loading conditions.…”