国产航空有机玻璃(PMMA)的非线性应力松弛行为研究

实验测定了国产航空有机玻璃PMMA在室温(20℃)、3—20.45％应变量范围内的应力松驰曲线。将用于表述中低应变率下加卸载循环的应力—应变行为的非线性本构理论,也即以考虑弹性和粘弹性变形的标准线性体和考虑塑性变形的活化粘壶作串联耦合的本构模型扩展应用到应力松弛状态,给出了相应的本构理论方程。对实验测得的应力松弛曲线进行数值拟合计算,吻合结果良好。表明所提出的本构模型也适用于描述PMMA的非线性应力松弛行为。得到了平衡态的应力一应变曲线,曲线的单调变化,表明不存在屈服极大值及以后的应变软化效应。

ON NONLINEAR STRESS RELAXATION BEHAVIOUR OF POLYMER PMMA

The stress relaxation curves of PMMA in the strains range of 3-20. 45% and at room temperature are measured. The nonlinear constitutive model, which is originally used to describe the stressstrain behaviour of loading and unloading cycle, and its content is composed of an activation dashpot in series couple with a standard linear solid, has been extended to express the stress relaxation behaviour. The corresponding equation of constitutive model is worked out. The results of theoretical calculation are in good agreement with the experimentally measured curves. The equilibrium stress-strain curve is obtained. The curve of monotonous change shows that the yield maximum and following strain-softening are disappeared.