Research Of Equivalent Fracture Strain And Equivalent Fracture Stress In Small Punch Test

In this paper, a large number of different materials are selected to do the small punch test. A deeply research was carried out about GTN model, equivalent stress and strain in finite element simulation of the small punch test. Taking16MnR as a example to do some analysis and calculation. According to this paper, the main achievements are as follows:(1) Make a lot of conventional tensile tests and small punch tests of many different materials in electric power, petrochemical and chemical industry.(2) The yield load Fp in small punch test load-displacement curve was determined using a method of "the least square method". As result of the analysis, the empirical linear relationship between the Fp and yield strength Rel could be expressed. Also the empirical linear relationship between the maximum load Fm and the tensile strength Rm did the same.(3) A new method about how to confirm GTN model parameters was proposed. Taking the example of16MnR material, we used the this method to get GTN parameters, and put forward a new parameter to judge whether GTN model parameters are correct or not.(4) A theoretical formula of equivalent strain in the fracture position of the small punch sample has been proposed.(5) Using ASME Local Strain Limit Criterion to calculate the equivalent failure strain, and compare it with the limit strain of the tensile test.