基于摩擦修正的SA508-3钢高温本构方程

High-temperature constitutive equation of SA508-3 steel based on friction correction

采用Gleeble-1500D热模拟试验机对SA508-3钢在温度为1073~1473 K、应变速率为0.001~1 s^-1时进行了热压缩实验,获得了既定变形条件下的SA508-3钢的高温应力-应变曲线。采用膨胀系数对试样尺寸进行评估,数据显示:摩擦对热压缩过程的影响显著,实验所得的应力不能正确表示材料的真实应力。采用变形功法对实验数据进行了修正,结果表明:摩擦修正前后的真应力-真应变曲线具有相同的变化趋势,但修正后的真应力值始终小于实验测量的应力值,且随着变形程度的增加,修正前后的真应力值之差逐步增大。针对修正后的真应力-真应变曲线,通过数据拟合确定了SA508-3钢的双曲正弦本构方程。通过平均绝对相对误差(6.26%)和相关性系数(0.998)验证了所构建本构方程的准确性。

Hot compression experiments for SA508-3 steel were carried out by thermal-mechanical simulator Gleeble-1500 D with the temperature of 1073-1473 K and the strain rate of 0.001-1 s^-1,and the stress-strain curves of SA508-3 steel were obtained under the given deformation conditions.Then,the deformed specimen sizes were evaluated by expansion coefficient.And the data show that the friction has obvious effect on the hot compression deformation of specimens.Due to obvious friction effect,the stress obtained from the experiment can not accurately represent the true stress of material,and the experimental data were modified by the deformation work method.The results show that the stress-strain curves before and after friction correction have the same changing trend,and the modified stress value is always smaller than the experimental stress value.With the increasing of deformation degree,the difference between modified and experimental stress values increases.According to the modified stress-strain curves,the hyperbolic sine constitutive equation of SA508-3 steel is determined by data fitting,and the accuracy of the constitutive equations is verified by the average absolute relative deviation of 6.26%and the relative coefficient of 0.998.