Liu Xiu, Liu Chen, Zhu Dingxiang, Lin Jianguo
School of Mechanical Engineering and Mechanics, Xiangtan University, Xiangtan 411105, China.
School of Civil Engineering, Xiangtan University, Xiangtan 411105, China.
Polymers (Basel). 2023 Aug 12;15(16):3388. doi: 10.3390/polym15163388.
Uniaxial and biaxial cyclic tensile tests and stress relaxation tests were performed on the ethylene propylene diene monomer (EPDM) material to investigate its stress-softening effect. The experimental results reveal that the EPDM material presents a significant Mullins effect during the cyclic stretching processes. Furthermore, it is found that the deformation of the EPDM material does not return to zero simultaneously with the stress, due to the viscoelasticity of the EPDM material. Therefore, this study combines pseudo-elasticity theory and viscoelastic theory to propose a visco-hyperelastic constitutive model. The proposed model is used to fit and analyze the uniaxial and biaxial cyclic test results of EPDM and a comparison is conducted with the corresponding hyper-elastic constitutive model. The results show that the proposed model is in good agreement with the experimental data and superior to the hyper-elastic constitutive model, especially when it comes to the stress-softening unloading process. This work is conducive to accurately characterizing the stress-softening behavior of rubber-like materials at large deformation and can provide some theoretical guidance for their widespread application in industry.
对三元乙丙橡胶（EPDM）材料进行了单轴和双轴循环拉伸试验以及应力松弛试验，以研究其应力软化效应。实验结果表明，EPDM材料在循环拉伸过程中呈现出显著的穆林斯效应。此外，由于EPDM材料的粘弹性，发现EPDM材料的变形不会与应力同时恢复到零。因此，本研究结合伪弹性理论和粘弹性理论，提出了一种粘弹性超弹性本构模型。所提出的模型用于拟合和分析EPDM的单轴和双轴循环试验结果，并与相应的超弹性本构模型进行比较。结果表明，所提出的模型与实验数据吻合良好，且优于超弹性本构模型，特别是在应力软化卸载过程中。这项工作有助于准确表征大变形下类橡胶材料的应力软化行为，并可为其在工业中的广泛应用提供一些理论指导。
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