Analysis of fracture behavior and stress-strain distribution of martensite/austenite multilayered metallic sheet

摘要

The properties of a multilayered metallic sheet tend to be different from those of a sheet made of monolithic material because of the layer interaction. Because of the change in the ductility and strength of each layer, the stress gradient changes; a brittle layer is deformed over the fracture limit of the monolithic material. Further, a new stress-strain distribution is observed in the form of a new fracture within materials. In the case that the observed strain is more than the fracture strain of a monolithic brittle material, micro-voids and cracks are generated and a tunnel crack is formed. As the layer interaction is changed by the suppression stress in the direction of necking, the stress components of two layers are changed. The suppression stress changes the features of the plastic zone, such as the defects range of dislocation, slip band, and void; consequently, the fracture strain is changed. The thinner the brittle layer, the greater is the increase in the fracture strain. This study suggests a method for predicting the fracture strain from the relation of the thickness change and the volume fraction in accordance with the lamination numbers.