Refined Model for the Stress-Strain Curve of Austenitic Stainless-Steel Materials at Elevated Temperatures

Abstract

Based on the room-temperature and high-temperature test method (steady state and transient state), a series of mechanical property tensile tests was carried out on S30408 (AISI304) austenitic stainless-steel materials. There were 72 specimens in total, including 8 specimens at room temperature, 28 specimens for a high-temperature steady-state test, and 36 specimens for a high-temperature transient-state test. Through the experimental investigation, the mechanical properties of stainless steel at room and elevated temperatures were obtained. The stress-strain curves of stainless steel at elevated temperatures were given and the development laws in a large range of strain were revealed. The tensile test results show that (1) with increasing temperature, the mechanical properties (elastic modulus, yield strength, and ultimate strength) of stainless steel continuously decrease; (2) the nominal yield strength of stainless steel in corner areas is higher than that in flat areas at the same temperature; and (3) the test loading rate has a significant effect on the stress-strain curve of stainless steel at elevated temperatures; with a higher loading rate, all strength indexes of stainless steel at elevated temperatures are improved. In this paper, a theoretical model for stress-strain curves of stainless steel at elevated temperatures, containing five mechanical property parameters, was developed by theoretical derivation, and the accuracy of the theoretical model was verified by experimental results. Next, the high-temperature reduction coefficients of the five mechanical property parameters in the theoretical model were analyzed by numerical simulation, their calculation formulas were fitted, and a reliability analysis was carried out on the five parameters using SPSS. Finally, a complete theoretical model of the stress-strain curve of stainless steel at elevated temperatures was proposed that can accurately predict the mechanical properties of austenitic stainless steel at elevated temperatures.