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首页> 外文期刊>International Journal of Plasticity >A finite strain thermodynamically-based constitutive modeling and analysis of viscoelastic-viscoplastic deformation behavior of glassy polymers
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A finite strain thermodynamically-based constitutive modeling and analysis of viscoelastic-viscoplastic deformation behavior of glassy polymers

机译：基于玻璃聚合物粘弹性粘塑变形行为的有限菌株基于热力学的组成型建模及分析

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摘要

In elastic and plastic deformation of glassy polymers and with the increase of deformation, the material would exhibit elastic, viscoelastic, and viscoelastic-viscoplastic (VE-VP) responses in sequence. These deformation behaviors should be constitutively modeled in such a way to accurately and efficiently simulate many important physical behaviors and phenomena involved in polymer deformation and processing. The elastic and viscoelastic deformation behavior in the pre-yield region can be well represented by the existing Constitutive models. However, the VE-VP response in the post-yield region, such as stress relaxation and strain recovery behaviors, cannot be well modeled yet. In this research, a series of uniaxial compression tests of the stress relaxation and the loading-unloading-recovery behaviors of glassy polymer were firstly carried out. The experimental phenomena show strain-rate-dependent characteristics that cannot be explained by the thermally-activated viscosity/viscoplasticity theory. Therefore, it is proposed that a glassy polymer can be treated as a glassy network linked by the secondary bonds and entanglements; while the glassy network is locally yielded and elastically distorted in the pre-yield region, giving rise to a glassy network resistance (GNR) which accounts for the strain-rate-dependent characteristics. A finite strain thermodynamically-based constitutive model was then proposed to incorporate the effects of the GNR. Finally, the newly proposed model was calibrated and its predictive capability was elaborated with the comparison of experiments as well as two widely reported models. The predicted results demonstrate that the GNR is critical in controlling the post-yield stress relaxation and strain recovery. In addition, the nonlinear evolution of the GNR plays a key role in controlling the nonlinear pre-peak hardening and the nonlinear unloading curve. This research thus not only provides a new constitutive theory for modeling of the VE-VP deformation behavior of glassy polymers, but also advances the understanding of the mechanical responses of glassy polymers in deformation process.
机译：在玻璃聚合物的弹性和塑性变形和随着变形的增加，材料将显示弹性，粘弹性和粘弹性粘弹性（Ve-VP）依次反应。这些变形行为应以这种方式组成，以便准确，有效地模拟聚合物变形和加工中涉及的许多重要的物理行为和现象。预屈服区中的弹性和粘弹性变形行为可以通过现有的本构模型很好地表示。然而，屈服地区的Ve-VP响应，例如应力松弛和应变恢复行为，尚未充分建模。在本研究中，首先进行了一系列应力松弛和玻璃聚合物的卸载恢复行为的一系列单轴压缩试验。实验现象显示出应变率依赖性特征，其无法通过热活化的粘度/粘塑性理论解释。因此，提出玻璃状聚合物可以被视为由二次键和缠结连接的玻璃状网络;虽然玻璃网络在预屈服区域中局部产生并弹性变形，但导致玻璃状电阻（GNR），其占应变率依赖性特征。然后提出了有限应变的基于热力学的本构模型来掺入GNR的效果。最后，校准了新提出的模型，并在实验的比较以及两个广泛报告的模型中阐述了其预测能力。预测结果表明，GNR对于控制后产率应力松弛和应变恢复至关重要。另外，GNR的非线性演化在控制非线性预峰硬化和非线性卸载曲线中起着关键作用。因此，该研究不仅为玻璃聚合物的Ve-VP变形行为的建模提供了新的组成型理论，而且还推进了对变形过程中玻璃聚合物的机械响应的理解。

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