Critical Poisson’s ratio between toughness and brittleness

Abstract

We have a new understanding on a unified fracture criterion based on two kinds of strain energy density. A definite expression which is a function of Poisson’s ratio to describe a crucial parameter in the unified fracture criterion is derived. The critical value of Poisson’s ratio between brittle and ductile materials can be derived as 2/7 which is verified by experimental data. Besides, the effect of Poisson’s ratio on the fracture loci in stress spaces is studied using unified fracture criterion. It is found that the decrease in Poisson’s ratio increases the asymmetry of fracture loci between tensile stress states and compressive stress states in principal stress spaces and between Lode parameters are 1 and −1 in deviatoric-stress spaces. In addition, stress triaxiality has a great effect on the fracture behaviour with different Poisson’s ratios.

Keywords:

• Fracture
• Poisson’s ratio
• metallic glasses
• fracture loci
• brittle-ductile transition

Acknowledgements

The authors are very grateful for the support received from the National Natural Science Foundation of China [grant number 51275414], the Fundamental Research Funds for the Central Universities with [grant number 3102015BJ (II) ZS007], the National College Students Innovation Experiment Program [grant number 201510699063].