Experimental Research On The Influence Of Plastic Deformation On Fracture Mechanisms Of Engineering Materials

It is very important to study materials' fracture in the engineering.With the increase of plastic deformation,fracture criteria become more multiplicity and complex,a number of high strength and toughness of the material at break can't explain.This paper studies the influence of plastic deformation on the fracture mechanism of engineering materials through experimental research,numerical calculation,the method of elastic deformation and plastic deformation separating.The main contents are as follows:(1)According to the mechanism of elastic-plastic deformation of metal materials,preliminary recognizing plastic deformation may not the factor of material fracture mechanism.(2)The experimental analysis and quantitative calculation of several conventional metallic material fracture.By macroscopic and microscopic experimental phenomena fracture surface and fracture curves under different stress states for different materials,we can know that in the process of fracture,the grater of plastic deformation of material,the higher bearing capacity of fracture,the more energy will be absorbed in the former of fracture,the more difficult material damage.(3)Conduct the theory and numerical calculations for crack tip tension-shear stress field,which can be obtained the fracture law is same with the test results under plane strain state.In the near ? type crack,the maximum principal stress in position of the maximum stress triaxiality,which is the fracture direction of normal fracture with void;the maximum shear stress in position of the maximum stress triaxiality,which is the fracture direction of shear fracture with void;and the direction of maximum shear stress in position of the maximum shear stress,which is the fracture direction of shear fracture without void.(4)Recognize that different fracture mechanisms,mainly because of the different sizes of plastic deformation under different materials for different stress states,and make new interpretations with related experiments.(5)When plastic deformation is small,making the preliminary discussions for the splitting phenomenon of gypsum.