Study On Ductile-brittle Transition Temperature Of Materials By Small Punch Test

Small punch test (SPT) can be used to obtain mechanical properties of materials by miniature size specimen. As the small punch specimen is very little and can be sampled from the serviced equipment, the small punch test provides a reliable basis for residual assessment and structure integrity. In this paper, nineteen kinds of materials which are commonly in pressure vessel were used for studying the ductile-brittle transition temperature by the small punch test. The main contents and conclusions of the thesis are as follows:(1) The test program of ductile-brittle transition temperature by low-temperature small punch study was developed. The small punch test from room temperature to-196℃(liquid nitrogen temperature) and Charpy impact test for nineteen kinds of materials were carried out.(2) The SPT transition temperature which was got by the energy method was used to empirical association study with transition temperature of the impact test. The empirical association of transition temperature should be the same kind of material because the correlation for the same kind of material is very good.(3) The thickness of SPT sample was studied. As the temperature decreased, the minimum thickness and the bottom thickness of the specimens was gradually increased. The thickness didn’t change when the temperature to a certain temperature. A new method based on the minimum thickness of thinning rate was proposed to determine the transition temperature of SPT.(4) The new structural specimens, including different thickness specimens, U-notch grooves and V-notch specimens, were introduced to studied effect of the sample structure on the transition temperature. The structure had an effect on the transition temperature.