SU  Xiangting

(Mechanical Department)

Abstract:  The property of Materials in deformation and fracture is an important basis for the design and manufacture in engineering.Up till now, there have been some research  viewpoints on the deformation and fracture of material.This academic thesis analyzes the macrostructu of metal materials for the elastic causally  between the inside micro crystal and the outward macrostructure of materials in tension.The mechanism for plastic deformation of materials in tension may be analyzed by theory of displocation.The flow limit and flow limit stress of materials in tension should be analyzed for shear strength.Author should compare the analysis result with the test reslut. Finally,a few dissents may be proposed.

Keywords: yield beilt; limit shear stress; fracture  toughness; displocation