聚乙烯拉伸应变速率的本构方程改进及运用

目的 对等密度、恒温条件下聚乙烯（PE）在不同应变率下的力学性能进行研究，改进原有本构方程的应变率项。方法 使用万能材料试验机，测量不同拉伸速率下PE的应力-应变曲线，并研究随着应变速率的增加，最大拉伸强度和断裂伸长率的变化趋势；基于Sherwood-Frost本构模型，对经典的热激活机制Seeger模型添加幂函数项，实现应变率与应变的耦合；基于最小二乘法，采用Matlab软件拟合本构模型参数，并将本构方程拟合结果与300，400，500 mm/min速率下的试验数据进行对比。结果 改进后的本构模型拟合数据与试验结果具有更高的吻合度，最大误差为8.12%，出现在300 mm/min的速度条件下。结论 随着拉伸速率的增加，PE材料的最大拉伸强度逐渐增加，断裂伸长率逐渐降低；改进应变率项后，本构模型具有更高的拟合精度，能够为有限元分析提供准确的材料参数。

Improvement and Application of Constitutive Equation for Tensile Strain Rate of Polyethylene

The project aims to study the mechanical properties of polyethylene (PE) at different strain rates in equal density and constant temperature conditions, and to improve the strain rate term of the original constitutive equation. The stress-strain curves of PE at different strain rates were measured with a universal material testing machine, and the variation trend of maximum tensile strength and elongation at break was studied with the increase of strain rate; Based on the Sherwood-Frost constitutive model, the power function term was added to Seeger model of classical thermal activation mechanism to realize the coupling of strain rate and strain; Based on the least square method, the parameters of the constitutive model were fitted with the software of Matlab, and the fitting results of the constitutive equation were compared with the experimental data at the rates of 300, 400, 500 mm/min. The fitting data of the improved constitutive model were more consistent with the experimental results. The maximum error was 8.12%, which occurred at the speed of 300 mm/min. With the increase of tensile rate, the maximum tensile strength of PE material increases gradually, while the elongation at break decreases gradually; after improving the strain rate term, the constitutive model has higher fitting accuracy and can provide accurate material parameters for finite element analysis.