The uniaxial tension experiments are performed on thermoplastic polyurethane to investigate its mechanical behaviors and related potential mechanisms, and the loading strain rate is designing to be wide ranging from 0.0001 to 1 s⁻¹. It is found that the polyurethane presents an obvious rate‐dependence, and the stress strain curves share distinct strain hardening characteristics under the investigated strain rates. Furthermore, the strain hardening ratios are sharing nearly same trends and appear to be influenced by both strain rate and the induced adiabatic heating. Besides, the ratio is also strain‐dependent on previous loading history. Then, a two‐dimension unit cell model is built to investigate potential equivalent mechanisms, of which the hard phase as inclusion is equivalent with crystallization zone, crosslinking sites, and so forth. The simulation results facilitate to explain the distinct strain hardening ratios, even for the matrix from the extrapolated curves under super‐low strain rate loading. Finally, the analogic mechanisms of equivalent hard inclusions are proposed, which can reasonably explain the strain rate‐ and strain‐dependence characteristics of polyurethane mechanical behaviors.

中文翻译：

---

各种应变速率载荷下聚氨酯的应变硬化行为及其机理

在热塑性聚氨酯上进行了单轴拉伸实验，以研究其机械性能和相关的潜在机理，并且将载荷应变率设计为从0.0001到1 s ^-1。结果表明，聚氨酯具有明显的速率依赖性，在所研究的应变速率下，应力应变曲线具有明显的应变硬化特性。此外，应变硬化率具有几乎相同的趋势，并且似乎受到应变率和绝热加热的影响。此外，该比率还取决于先前的加载历史。然后，建立一个二维晶胞模型来研究潜在的等效机理，其中包括的硬相与结晶区，交联部位等是等效的。仿真结果有助于解释不同的应变硬化率，即使是在超低应变率载荷下从外推曲线得出的基体。最后，