Research on High-Temperature Constitutive Models of Q355 and Q960 Steels

To investigate the applicability of the Wang model for stress-strain curves covering the entire tensile process across different steel types， typical low-alloy high-strength structural steel Q355 and high-strength steel Q960 were selected. The laws of mechanical property changes of these two steel types within the temperature range of 20 - 700 ℃ were obtained， and high-temperature constitutive models fully reflecting the elastic， plastic， and failure stages were established based on experiment data. First， tensile tests were conducted on 36 material specimens at both ambient and elevated temperatures. The complete stress-strain curves， covering elastic， plastic， and failure stages， were obtained. Based on experimental data， fitting formulas for the reduction factors of key parameters-including elastic modulus， yield strength， tensile strength， and fracture strain-were derived as functions of temperature. Subsequently， the Wang model， incorporating a descending branch， was employed to construct the high-temperature stress-strain relations for both steels， and its applicability was validated against experimental results. The findings demonstrate that the proposed temperature-dependent reduction factor formulas enable accurate determination of key mechanical parameters at varying temperatures. By integrating these parameters into the Wang model， the full-range stress-strain curves of Q355 and Q960 steels from loading to fracture （20 - 700 ℃） were successfully predicted， comprehensively capturing their elastic， plastic， and failure behaviors.