Li Yan, Luo Wenbo, Li Maodong, Yang Bo, Liu Xiu
College of Civil Engineering and Mechanics, Xiangtan University, Xiangtan 411105, China.
Department of Civil Engineering, Changsha University, Changsha 410022, China.
Polymers (Basel). 2022 Mar 27;14(7):1357. doi: 10.3390/polym14071357.
It is not conservative to directly use the strength tested under the laboratory loading rates to evaluate the long-term creep strength of polymers. A suitable strain rate-dependent constitutive model is crucial for accurately predicting the long-term strength and mechanical behavior of polymer pressure pipes. In this study, the Kondner hyperbolic constitutive model is considered the base model in deriving the rate-dependent constitutive model for PE100 pipe material, and the yield stress and initial tangent modulus are the two rate-dependent parameters of the model. Uniaxial tension tests are carried out under five specified strain rates ranging from 10 s to 5 × 10 s to obtain these two parameters. It is demonstrated that the strain rate dependence of the yield stress and the initial tangent modulus can be described by either a power or a logarithm law. The predictions from the two models are in good agreement with the experiments. In contrast, the power-law rate-dependent Kondner model is more suitable for describing the rate-dependent tensile behavior of PE100 pipe material than the logarithm-law rate-dependent Kondner model, especially for the cases of very low strain rates which relate to the polymer pressure pipe applications.
直接使用在实验室加载速率下测试的强度来评估聚合物的长期蠕变强度是不保守的。一个合适的应变率相关本构模型对于准确预测聚合物压力管道的长期强度和力学行为至关重要。在本研究中，Kondner双曲线本构模型被视为推导PE100管材应变率相关本构模型的基础模型，屈服应力和初始切线模量是该模型的两个应变率相关参数。在从10⁻⁵ s⁻¹到5×10⁻¹ s⁻¹的五个指定应变率下进行单轴拉伸试验以获得这两个参数。结果表明，屈服应力和初始切线模量的应变率依赖性可以用幂律或对数律来描述。这两个模型的预测结果与实验结果吻合良好。相比之下，幂律应变率相关的Kondner模型比对数律应变率相关的Kondner模型更适合描述PE100管材的应变率相关拉伸行为，特别是对于与聚合物压力管道应用相关的极低应变率情况。
