Study on yield strength of Q345R by energy method of small punch test

As a new method with little damage, small punch test (SPT) technique can evaluate mechanical properties of in-service component materials. This article introduced the energy method of small punch test based on elastic energy theory to predict the yield strength. Meanwhile, the experimental principle and procedures were described in detail. The experimental results of SPT energy method for Q345 were compared with those of conventional tensile tests, small punch offset method and two-tangent method. The results showed that the error of energy method was 5.52%, much lower than the errors calculated by offset method and two-tangent method. The effects of sample thickness, steel ball diameter, center hole diameter of the lower die, punching velocity and edge thickness decreasing on SPT results were analyzed by finite element analysis (FEA), based on Load-displacement (L-D) curve and Energy-displacement (E-D) curve. The optimal parameters were proposed as the sample thickness 0.5 mm, the steel ball diameter 2.4 mm and the center hole diameter of the lower die 4 mm.