Mahajan Dhiraj K, Singh Bhupinder, Basu Sumit
Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, UP, India.
Phys Rev E Stat Nonlin Soft Matter Phys. 2010 Jul;82(1 Pt 1):011803. doi: 10.1103/PhysRevE.82.011803. Epub 2010 Jul 27.
Cavitation in glassy polymers is known to result from highly triaxial states of local stress and the presence of impurities. Understanding of cavitation, particularly void nucleation, is important as cavities are precursors to crazes, which in turn lead to fracture. In this work we study the early stages of void nucleation in glassy amorphous polymers by imposing, in well designed molecular dynamics simulations, highly triaxial states of stress on ensembles of entangled linear macromolecular chains and monitoring the evolution of the entanglement network. Our results demonstrate that deformation induced disentanglement and rearrangement of topological constraints along individual chains play an important role in the early stages of void nucleation. Even in the glassy state, deformation causes significant changes in the rheological constraints on a chain though the number of interchain binary contacts may not change much.
众所周知，玻璃态聚合物中的空化现象是由局部应力的高三轴状态和杂质的存在引起的。由于空洞是银纹的前驱体，而银纹又会导致断裂，因此了解空化现象，尤其是空洞形核，非常重要。在这项工作中，我们通过精心设计的分子动力学模拟，对缠结的线性大分子链集合施加高三轴应力状态，并监测缠结网络的演化，来研究玻璃态非晶聚合物中空洞形核的早期阶段。我们的结果表明，变形诱导的沿单个链的拓扑约束的解缠和重排在空洞形核的早期阶段起着重要作用。即使在玻璃态，尽管链间二元接触的数量可能变化不大，但变形会导致对链的流变约束发生显著变化。
