Dynamic mechanical properties of austenitic stainless steel
The principal aim of the research is to determine the stress/strain characteristics of stainless steels at high rates of strain (> 100sec-1), and so to investigate the effects of changing strain rate on yield point and plastic flow stress. The material properties obtained in this work are intended for use in the analysis of explosive tests on model fast breeder reactor containment vessels. The experimental technique used is the split Hopkinson pressure bar method in which stress pulses are used to produce high rates of loading in the sample. Practical problems with pulse measurement and sample preparation are discussed, and recommendations are made to improve the reliability and accuracy of tests. New techniques described include the use of a transient recorder and micro-computer for improving pulse recording and analysis, pulse-shaping to control the strain rate of tests and a modification of the basic Hopkinson bar to enable a simple conversion to be made from compressive to tensile testing. The results of extensive testing of samples from 321 stainless steel bar in compression and tension over a wide range of strain rates (static and 100 to 2000sec-1), testing temperatures (20 to 6000C); and different annealing temperatures are reported. Results of tests on 304,316,321 and 325 stainless steel rod are also presented. Comparison with previous empirical and theoretical material constitutive equations is discussed.