Abstract

This work studies the tensile behavior of polyamide 6 (PA6) at different strain rates using both experimental and numerical methods. Quasi-static and dynamic tensile tests are performed using a universal testing machine and a split Hopkinson tensile bar (SHTB). The stress-strain curves and specimen morphologies are obtained over a wide range of strain rates from 2.6 × 10^–4 s^–1 to 900 s^–1. The tensile behavior of PA6 is sensitive to strain rate, and the yield strength and yield strain both increase with an increase of strain rate. The plastic stage of PA6 exhibits strain hardening characteristics under quasi-static loading, but strain softening characteristics under dynamic loading. The strain softening characteristics become more significant with an increase of strain rate. The quasi-static tensile mechanical responses of PA6 are analyzed by a ZWT viscoelastic constitutive model, while the dynamic ones are analyzed by a ZWT model with a damage factor. The experimental stress-strain curves are well described by the constitutive model. Three-dimensional incremental expressions of the constitutive model are given, and a user-defined constitutive subroutine is written. Numerical simulations on the stress wave propagation process and the stress-strain curves of PA6 under SHTB loading are conducted, with results that are consistent with the experiments.

中文翻译：

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不同应变率下聚酰胺 6 的动态拉伸行为：实验和本构模型

摘要

这项工作使用实验和数值方法研究了聚酰胺 6 (PA6) 在不同应变率下的拉伸行为。使用万能试验机和分体式霍普金森拉伸杆 (SHTB) 进行准静态和动态拉伸测试。应力-应变曲线和样品形态是在2.6 × 10 ^–4 s ^–1至900 s ^–1的广泛应变率范围内获得的。PA6的拉伸行为对应变速率敏感，屈服强度和屈服应变均随应变速率的增大而增大。PA6的塑性阶段在准静态载荷下表现出应变硬化特性，但在动态载荷下表现出应变软化特性。随着应变速率的增加，应变软化特性变得更加显着。PA6的准静态拉伸力学响应采用ZWT粘弹性本构模型进行分析，而动态拉伸力学响应则采用带有损伤因子的ZWT模型进行分析。本构模型很好地描述了实验应力-应变曲线。给出了本构模型的三维增量表达式，并编写了用户自定义的本构子程序。对SHTB加载下PA6的应力波传播过程和应力应变曲线进行了数值模拟，结果与实验结果一致。