An analysis of dynamic, ductile crack growth in a double edge cracked specimen

Abstract

Dynamic crack growth is analysed numerically for a plane strain double edge cracked specimen subject to symmetric impulsive tensile loading at the two ends. The material behavior is described in terms of an elastic-viscoplastic constitutive model that accounts for ductile fracture by the nucleation and subsequent growth of voids to coalescence. Two populations of second phase particles are represented, including large inclusions or inclusion colonies with low strength, which result in large voids near the crack tip at an early stage, and small second phase particles, which require large strains before cavities nucleate, The crack growth velocities determined here are entirely based on the ductile failure predictions of the material model, and thus the present study is free from ad hoe assumptions regarding appropriate dynamic crack growth criteria. Adiabatic heating due to plastic dissipation and the resulting thermal softening are accounted for in the analyses. Different prescribed impact velocities, inclusion spacings and values of the inclusion nucleation stress are considered. Predictions for the dynamic crack growth behavior and for the time variation of crack tip characterizing parameters are obtained for each case analyzed.

The Gurson-Tvergaard-Needleman-model for rate and temperature-dependent materials with isotropic and kinematic hardening

“…Without the Tvergaard and Needleman modi®cations accounting for the effect of void coalescence and stress controlled nucleation, Pan et al (1983) proposed a simple empirical equation for the strain rate and temperature dependence of the matrix material. This relationship was used by Needleman and Tvergaard (1991) for the numerical simulation of ductile fracture in isotropic materials under dynamic loading. Brocks et al (1995) studied the transferability of the damage parameters for visco-plastic materials by numerical cell-model calculations.…”

“…The visco-plastic strain rate relation can be expressed as follows (Pan et al 1983;Needleman and Tvergaard 1991): where e mp 0 is a reference strain rate, j is a material constant and gTY e mp speci®es the strain hardening characteristics and their dependence on temperature T.…”

Finite Element Based Physical Chemical Modeling of Corrosion in Magnesium Alloys

“…This approach can provide a better prediction of crack evolution and failure of AZ31 alloys in corrosive environment. The yield function of GTN damage model is described mathematically as [23],…”

Strength analysis of metallic bonded joints containing defects

“…The model was further developed by Tvergaad with respect to the yield condition and damage evolution [33,34] and by Needleman to include the law of void nucleation [35]. Therefore, the Gurson model used in present simulation can also be referenced as Gurson-Tvergaad-Needleman (GTN) model, which is an isotropic formulation that employs the invariants of the Cartesian components of the Cauchy stress (i.e., r ij ).…”