Abstract A series of quasi-static and dynamic uniaxial compression experiments over a wide range of temperatures were conducted on polyurea elastomer. The stress-strain response of polyurea exhibits extreme nonlinearity, temperature and strain-rate sensitivity. How to comprehensively describe these complex behaviors regulated by the unique micro-structure of polyurea is still an open question. In this paper, a nonlinear viscoelastic constitutive model for polyurea is developed. The nonlinear viscoelasticity, entropic and energetic elasticity are taken into account, correlated with the interaction of chain segments, the stretch of molecular chains and covalent bonds from the perspective of molecular structure. The viscoelastic response is formulated by the hereditary integral of relaxation modulus and strain rate with time. The real time is accelerated by shift factor, which depends on the free volume. A new mechanism of shear-induced increase of free volume, which gives rise to the nonlinearity of viscoelasticity, is proposed, and the corresponding rate-dependent evolution equation of fractional free volume is developed. Parameters in the model are determined through the compression experiments and DMA test. Comparison with experimental data, as well as the data from references, verifies the ability of the model to predict the nonlinear stress-strain response of polyurea over a wide range of temperatures and strain rates.

中文翻译：

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在很宽的应变率和温度范围内，基于自由体积的聚脲非线性粘弹性模型

摘要 对聚脲弹性体进行了一系列大温度范围内的准静态和动态单轴压缩实验。聚脲的应力-应变响应表现出极端的非线性、温度和应变率敏感性。如何全面描述由聚脲独特的微观结构调控的这些复杂行为仍然是一个悬而未决的问题。在本文中，开发了聚脲的非线性粘弹性本构模型。从分子结构的角度考虑了非线性粘弹性、熵弹性和能量弹性，与链段的相互作用、分子链的拉伸和共价键相关。粘弹性响应由松弛模量和应变率随时间的遗传积分公式化。实时时间由移位因子加速，这取决于自由体积。提出了一种新的剪切引起的自由体积增加的机制，该机制引起了粘弹性的非线性，并建立了相应的分数自由体积的速率相关演化方程。模型中的参数通过压缩实验和DMA测试确定。与实验数据以及参考数据的比较验证了模型预测聚脲在很宽的温度和应变率范围内的非线性应力应变响应的能力。并建立了相应的分数自由体积的速率相关演化方程。模型中的参数通过压缩实验和DMA测试确定。与实验数据以及参考数据的比较验证了模型预测聚脲在很宽的温度和应变率范围内的非线性应力应变响应的能力。并建立了相应的分数自由体积的速率相关演化方程。模型中的参数通过压缩实验和DMA测试确定。与实验数据以及参考数据的比较验证了模型预测聚脲在很宽的温度和应变率范围内的非线性应力应变响应的能力。