高强双相钢动态力学本构模型对比分析

Comparative analysis of dynamic mechanical constitutive model of high strength dual phase steel

研究了高强双相钢的动态力学特性和本构模型,以典型双相钢材料HC440/780DPD+Z为研究对象,对静态力学性能和应变速率为0.001、0.1、1、10、100、200、500和1000 s-1的动态力学特性进行了测试,获取了关键参数随应变速率的变化规律;采用多种经典本构模型方程对测试材料的本构模型参数进行了拟合,通过对比曲线拟合度发现,应变速率敏感性指数非线性的Johnson-Cook修正模型的拟合度最高;在此基础上,结合Swift模型和Hockett-Sherby模型,并引入应变速率强化项,构建了新的材料本构模型;对比Johnson-Cook修正模型和新模型的拟合相关度系数,并基于冲击试验对材料本构模型的有效性进行了对比验证。结果表明,所研究材料具有一定的应变速率敏感性;敏感性指数与应变速率呈非线性关系;采用引入应变速率强化项的综合Swift模型和Hockett-Sherby模型,拟合度达到0.98,且不随应变速率的增加而波动;冲击试验表明,通过新拟合模型获得的载荷-时间曲线与试验结果一致,关键参数的相对误差控制在5%以内,验证了新本构模型的准确性和可靠性。

The dynamic mechanical properties and constitutive model of high strength dual phase steel were studied.Taking typical dual phase steel HC440/780 DPD+Z as the research object,the static mechanical properties and dynamic mechanical properties at the strain rate of 0.001,0.1,1,10,100,200,500 and 1000 s-1 were tested,and the variation of key parameters with strain rate was obtained.Various classical constitutive model equations were used to fit the constitutive model parameters of the test materials,and by comparing the curve fitting degrees,it is found that the fitting degree of modified Johnson-Cook model with nonlinear strain rate sensitivity index is the highest.On this basis,a new material constitutive model was constructed by combining Swift model with Hockett-Sherby model and introducing strain rate strengthening term.The fitting correlation coefficients of modified Johnson-Cook model and new model were compared,and the validity of material constitutive model was compared based on impact test.The results show that the research material has certain strain rate sensitivity,and the sensitivity index has a nonlinear relationship with the strain rate.The fitting degree of the comprehensive Swift model and the Hockett-Sherby model with the introduction of strain rate strengthening term is 0.98,which does not fluctuate with the increase of strain rate.The impact test shows that the load-time curve obtained by the new fitting model is consistent with the test results,and the relative error of key parameters is controlled within 5%,which vertifies the accuracy and reliability of the new constitutive model.