Research Of Material Mechanical Properties By Small Punch Testing

Small Punch Testing (SPT) is one of the miniature specimen method to evaluate the mechanical property of in-service components. Due to the small size of the specimen, small punch test has a great application value in evaluating of mechanical properties of in-service pressure equipment.Small Punch tests, standard tensile test and fracture toughness tests were carried out in this paper. A lot of mechanical properties of materials were obtained. According to the analysis of the data, the main results were shown in the following:1). Formular about the elastic modulus by the SPT was deduced based on the model of simplified bending theory of the thin plane. A theoretical calculation between the slop(P/δ) of the first stage of SPT load-displacement curve and the elastic modulus was established.2). The yield load was proposed using a method of "the least square method". This method is easy to operate and can quickly get the yield load(Fp). As result of the analysis, the empirical linear relationship between the Fp and yield strength Rel can be expressed.3). The empirical correlation between Pmax and ultimate strength Rmax was established4). The relationship between the percentage elongation after fracture and the the length of arc after fracture of SPT was established.5).The existence of a significant relationship between the equivalent fracture strain at the point of failure(εeqf) and the conventional fracture toughness(JIC) was created. Size affects of SPT was studied. Small punch samples of small size show dimple fractures whereas large fracture toughness samples show quasi-cleavage fractures.