Small Punch Testing and Its Modeling for the Evaluation of Mechanical Properties of Heat-Resistant Steels

Small punch tests on miniaturized thin discs (SPT) can be considered as one of the promising methods predominantly for an assessment of the residual life of parts in service of power plants and thermal facilities. These tests can be used for determining a number of material properties. Two variations of the test seem to have a good potential for use in wide range of temperatures. The CF test (constant force) is a test in which the puncher penetrates under constant load and the time dependence of the deflection is measured. This test is similar to a conventional creep test. The CDR test (with constant deflection rate conditions), in which the puncher penetrates through the disc at a given constant rate of deflection (i.e., central deflection measured in a direction perpendicular to the disc) and the necessary force is measured. This mode of the tests can serve similarly as conventional tensile tests for determining of the static material properties, the estimation of fracture toughness and transitions in material behavior. The article summarizes the capabilities of the small punch technique and presents results from testing of two heat resistant steels, i.e., CSN 15313 and P91 used in the Czech power industry. Experimental results are compared with finite element modeling.