The influence of plasticity mismatch on the growth and coalescence of spheroidal voids on the bimaterial interface

To investigate the macro-mechanical response and micro-mechanism of damage by void growth and coalescence on the interface in a bimaterial system, detailed finite element computations of a representative cylindrical cell containing a spherical void are performed. By comparison with the response of a homogeneous material cell model, significant effects of the matrix plasticity mismatches due to the yield stress and the strain hardening exponent on the void growth and coalescence are revealed: (1) The growth rate of the void on the bimaterial interface is much faster than that in the homogeneous material, and the critical coalescence strain of the void on the interface is only about half of that in homogeneous material. (2) Due to the difference in the deformation resistance of the matrix materials in the bimaterial system, all computations indicate that deformed voids are seriously distorted and the linking of adjacent voids takes place in the softer matrix material. Comparison of the computational results with the classical Rice-Tracey (R-T) model shows that the R-T model cannot make good prediction for the growth of the void on the bimaterial interface. On the basis of large numbers of numerical simulations, a correction coefficient is introduced to improve the R-T model.