small punch test - Two methods of TSP temperature determination

Small punch test is very useful method for evaluation of actual material properties of components especially in power industry. Two standards cover small punch test method – European standard and ASTM standard. These standards unified the main parameters of small punch test set-up and correlation relationships for the evaluation of mechanical, fracture and creep properties. The paper deals with comparison of two methods for determination of T SP temperature used to evaluate DBTT. The historically used two-curve method relies on two distinctive energies - the fracture energy at the zero-point of the absolute temperature, that is determined by extrapolating the fitted function for the lower shelf, and the fracture energy at the intersection point between the fits for the lower and upper shelves. The method preferred by new standards calculates T SP temperature by fitting a tangential function in the similar way as various formulas used for evaluation of Charpy tests. Presented paper deals with an evaluation of T SP temperature by both methods. The effect of using both 2 mm and 2.5 mm diameter punches is assessed too.