Research On Fracture Characteristics Of Specimen Thickness In Small Punch Test

The research begins with the automation reconstruction of small punch test apparatus and software. Uniaxial tensile test and small punch test had been conducted, and ABAQUS was adopted to establish SPT model. The test process had been simulated based on the ductile elastoplastic damage theory of Gurson. According to the simulations and tests, the main results are shown in the following:(1) The physical performance of testing machine and the accuracy of test results had been improved through automation transformation.(2) Research on the relationship between friction coefficient, specimen thickness and L-D curve based on small punch test of different friction coefficient and different specimen thickness had been carried out. SEM was used to observe and analyse the fractography of different SPT specimens.(3) The ratios of equivalent maximum stress to maximum tensile stress, equivalent maximum stress to true stress calculated from maximum tensile stress and equivalent fracture strain to corresponding strain of maximum tensile stress are 1.96,1.17 and 1.01 respectively.(4) Simulations with different friction coefficient were conducted. It is shown that the smaller the friction coefficient is the closer the fracture position gets to the center of the specimen, and the larger the maximum Load is. The results of related tests in which lubricating oil is added between the steel ball and specimen agree well with that of simulations.(5) Based on the simulations of fracture process of specimens with different thickness, the relationship between fracture position and specimen thickness had been obtained which agreed well with that of the tests.