模具钢的高温变形行为及本构模型的建立

Deformation behavior at high temperature and establishment of constitutive model for die steel

准确的材料本构模型是有限元数值建模与模拟的基础和关键。在应变速率为0.001~10 s-1和变形温度为750~1150℃的条件下,进行了638模具钢热模拟实验,得到了其在不同条件下的应力-应变曲线,研究了其高温变形行为。结果表明,随着应变的增加,流动应力急速增大,达到峰值后缓慢减小并最终趋于平衡,这是材料加工硬化和动态软化综合作用的结果。对应力-应变曲线进行摩擦修正后,分别基于改进Johnson-Cook本构模型和应变补偿的Arrhenius本构模型建立了638模具钢本构模型,两者的平均相对误差分别为8.03%和7.66%,综合考虑所建本构模型的精确度和实际激光热处理中的高温、高应变速率情况,建议选用基于应变补偿的Arrhenius本构模型。

An accurate material constitutive model is the foundation and key of finite element numerical modeling and simulation.Therefore,the thermal simulation experiments of 638 die steel were carried out under the conditions of strain rate of 0.001-10 s'and deformation temperature of 750-1150 C,and its stress-strain curves under different conditions were obtained to analysis its high temperature deformation behavior.The results show that the flow stress increases sharply with the increasing of strain,and then decreases slowly and finally tends to equilibrium after reaching the peack,which is the result of the combined effect of work hardening and dynamic softening of the material.After friction correction of the stress-strain curve,the constitutive models of 638 die steel are established based on the improved Johnson-Cook model and the strain-compensated Arrhenius model,respectively,and the average relative errors of the two are 8.03%and 7.66%,respectively.Considering the accuracy of the constructed constitutive model and the condition of high temperature and high strain rate in the actual laser heat treatment,it is recommended to use the Arrhenius constitutive model based on strain compensation.