超高分子量聚乙烯材料的应力松弛研究

Study on the Stress Relaxation of Ultrahigh Molecular Weight Polyethylene

采用实验方法研究超高分子量聚乙烯(UHMWPE)材料,在不同温度、应变率和初始应变的条件下进行单轴压缩应力松弛实验,得出松弛应力与时间成非线性关系,且温度越高、应变率越大、初始应变越小,则最终稳定的应力值越小的结论.采用时间分数阶粘弹性模型,结合Boltzmann叠加原理推导出UHMWPE材料在整个加载段及松弛段的应力响应函数,并与实验数据最小二乘拟合.结果表明,时间分数阶Scott-Blair模型能很好地描述UHMWPE材料的粘弹性行为.

Mechanical property of UHMWPE was studied by uniaxial compression stress relaxation experiment.The experiments were carried out under different temperature,strain rate and initial strain.Experimental results showed that the relaxation stress changes nonlinearly with time.A higher temperature,a greater strain rate or a smaller initial strain all result in a smaller final stable stress.Using the time fractional Scott-Blair model and the Boltzmann superposition principle,the stress responses of UHMWPE material during the entire loading and relaxation periods were deduced.The experimental data were fitted to the theoretical model using the least squares method.Numerical results indicated that the time fractional Scott-Blair model can well describe the viscoelastic behavior of UHMWPE material.