S30408奥氏体不锈钢高温力学性能试验研究

不锈钢材料高温力学性能是不锈钢结构抗火设计与数值模拟分析的重要参数。相对于碳素钢，不锈钢材料具有强非线性、比例极限低、无明显屈服平台、各向异性、应变硬化显著等特点，高温下两种材料的力学性能存在着较大的差异。该文利用MTS810试验系统对S30408奥氏体不锈钢进行了常温、高温稳态和高温瞬态试验研究，并将试验结果与《欧洲规范》以及已有的研究结果进行了对比分析。利用稳态试验结果，对影响高温下不锈钢材料力学性能的硬化指数n_θ和m_θ进行了修正，提出高温下不锈钢材料本构关系表达式，并给出了高温下不锈钢材料的初始弹性模量、屈服强度和极限强度的折减系数。对比分析了稳态试验结果与瞬态试验结果，结果表明：通过两种试验方法获得的高温下不锈钢材料应力-应变曲线存在一定的差异；在温度600℃范围内，差异不明显，当温度超过600℃时，两者差异随温度升高而逐渐增大。

EXPERIMENTAL INVESTIGATION ON MECHANICAL PROPERTIES OF S30408 AUSTENITIC STAINLESS STEEL AT ELEVATED TEMPERATURES

The mechanical properties of stainless steel material at elevated temperatures are the key parameters for fire resistant design and numerical simulation analysis of stainless steel structures. Compared with carbon steel, stainless steel is an anisotropic material, with a stronger nonlinearity, a lower proportionality limit, and apparent strain-hardening, as well as having no obvious yield plateau. There were significant differences in the mechanical properties of the two materials at elevated temperatures. Based on MTS810 material testing system, tests at room temperature and steady and transient state tests at elevated temperatures were conducted on the mechanical properties of S30408 austenitic stainless steel. The test results were compared with European Code and other existed research results of stainless steel material. The parameters which influence (such as hardening indexes n_θ and m_θ ) the mechanical properties of stainless steel material at elevated temperatures were modified using the results of the steady state test. An expression of the constitutive relationship of stainless steel was proposed. The reduction factors of initial elasticity modulus, yield strength and ultimate strength at elevated temperatures were presented. By the comparisons between the results of steady state and transient state tests, the stress-strain curves obtained from the two methods slightly differed from each other. The differences were not obvious below 600℃, but the differences increased when temperature was higher than 600℃.