Evaluation Of Material Mechanical Properties By Small Punch Test At Low Temperatures

As a miniature specimen test technique, small punch test (SPT) can be approximated non-destructive to assess the properties of in-service device. In the paper, main research focus on the small punch test at low temperatures, summing up the characteristics with temperature changed. First, using the structured test device, the SPT of 16MnR, A508-III and A350 in three directions realized at different temperatures. The changes of the yield characteristic value and the maximum load in small punch test curve have the same trend with the yield strength and tensile strength of standard tensile test. The relationship at the same temperature level could be expressed by:16MnR:σs=1.61Ps+123.95,σb=167.79+0.25Pm; A508-Ⅲ:σs=1.95Ps+160.61. Then, followed by small punch energy versus with temperature, the ductile-brittle transition temperature Tsp by the small punch test can be determined. The Tsp has a linear correlation with the duct-brittle transition temperature TCVN of Charpy impact test: TCVN=8.1Tsp-478.4. Furthermore, according to the macro and micro fracture analysis in the beginning crack location, the species fracture belong to ductile fracture, gradually changed to brittle fracture at liquid nitrogen temperature. The thickness in necked increases with the temperature decrease, and oblique fracture transferred into straight fracture. Also researched on A350 material of three different directions, it can be determined the SPT is useful to determine material anisotropy, while the direction properties are consistent with the standard specimen.