发表机构
University of Akron（阿克伦大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文通过预切口纯剪切实验和偏振光学显微镜测量，阐明弹性体断裂中裂纹尖端应力决定网络寿命和裂纹速度，而非传统认为的速度决定撕裂能，并揭示了弹性极限和粘弹性条件下的因果关系。
AI 中文摘要
弹性体断裂的传统解释将撕裂能 G 视为由撕裂速度决定的输出量，该速度被认为等于裂纹速度 vc，并由此得出结论：更高的 vc 产生更大的粘弹性耗散，从而增大 G。基于空间和时间分辨的偏振光学显微镜（str-POM）对尖端应力的测量，我们利用预切口纯剪切实验来阐明因果关系：局部裂纹尖端应力决定网络寿命，使 vc 成为被动的动力学输出。在良好交联的弹性体于较宽温度范围内易于实现的弹性极限中，Rivlin-Thomas 标度成立，且 vc 仅取决于施加的应变，与拉伸速率无关，表明 vc 与尖端应力之间存在一一对应关系。在通过降低交联密度制成的高可拉伸弹性体中，随着与速率相关的粘弹性过程出现并影响网络寿命，vc 不再与远场载荷良好关联。由于流变效应影响弹性体网络中链张力建立的方式，在相同的名义应变下，以更高的拉伸速率施加时 vc 更高。这证实了不同的拉伸速率产生不同水平的尖端应力，但相同的尖端应力仍产生相同的 vc。通过 str-POM 测量，我们还能够阐明温度依赖性的本质：在给定的尖端应力下，较低温度下裂纹扩展较慢；反之，在较低温度下，产生相同的 vc 需要更高的尖端应力。
英文摘要
The conventional interpretation of elastomeric fracture treats the tearing energy G as an output determined by tear speed, taken to equal crack velocity vc, concluding that higher vc produced greater viscoelastic dissipation to increase G. Based on spatially and temporally resolved polarized optical microscopic (str-POM) measurements of tip stress tip stress, we use prenotched pure shear experiments to clarify the causality: Local crack-tip stress determines the network lifetime, making vc the passive kinetic output. In the elastic limit that can be readily achieved for a well crosslinked elastomer in a wide range of temperatures, Rivlin-Thomas scaling holds, and vc depends only on the applied strain, independent of stretch rate, indicating one-to-one correspondence between vc and tip stress. In a highly stretchable elastomer made with reduced crosslink density, vc no longer correlates well with the far-field load as rate-dependent viscoelastic processes emerge to affect network lifetime. Because of the rheological effects on how chain tension builds in the elastomeric network, vc is higher at a common nominal strain when it is imposed with higher stretch rate. confirm that different stretch rates produce different levels of tip stress. The same tip stress still produces the same vc. With str-POM measurements we are also able to elucidate the nature of temperature dependence: at a given tip stress,, crack growth is slower at lower temperatures; conversely it requires higher tip stress to produce the same vc at lower temperatures.
