Strain based investigation of mode I crack near strong-weak interface in SSY regime

Abstract

The paper presents an investigation on mode I cracked bi-material comprising elastic-plastic materials that are elastically identical but have different yield strengths and plasticity properties. The interface between the materials is considered to be thin and perfect. A strain based theoretical model is used to include the effect of non-linearity in plasticity characteristics of materials for estimation of the magnitude of plastic energy transfer across the interface when the crack in stronger material is near the interface of weaker material in SSY regime. Energy transfer is quantified by the component of energy release rate of the crack due to inhomogeneity caused by property mismatch between the materials. The behaviour of the model is demonstrated at discrete positions of crack near the interface of strength and plasticity mismatched steels under the action of monotonic tension in plane stress condition. Amplification effect due to energy transfer towards stronger steel is found to result in higher values of energy release rate and stress intensity parameter at the crack tip vis-à-vis the far field values. The effect is maximum when the crack tip is at the interface of steels. The results are compared with those of an available model based on Dugdale's criterion that uses stress parameter and is applicable to elastic-perfectly plastic materials. Difference is noticed between the two. Finite element analysis of the bi-material is undertaken to validate the present model. Numerical and theoretical results are found to be in close agreement.