Gurrutxaga-Lerma Beñat, Balint Daniel S, Dini Daniele, Eakins Daniel E, Sutton Adrian P
Department of Mechanical Engineering Imperial College London, London SW7 2AZ, United Kingdom.
Department of Physics Imperial College London, London SW7 2AZ, United Kingdom.
Phys Rev Lett. 2015 May 1;114(17):174301. doi: 10.1103/PhysRevLett.114.174301. Epub 2015 Apr 28.
When a metal is subjected to extremely rapid compression, a shock wave is launched that generates dislocations as it propagates. The shock wave evolves into a characteristic two-wave structure, with an elastic wave preceding a plastic front. It has been known for more than six decades that the amplitude of the elastic wave decays the farther it travels into the metal: this is known as "the decay of the elastic precursor." The amplitude of the elastic precursor is a dynamic yield point because it marks the transition from elastic to plastic behavior. In this Letter we provide a full explanation of this attenuation using the first method of dislocation dynamics to treat the time dependence of the elastic fields of dislocations explicitly. We show that the decay of the elastic precursor is a result of the interference of the elastic shock wave with elastic waves emanating from dislocations nucleated in the shock front. Our simulations reproduce quantitatively recent experiments on the decay of the elastic precursor in aluminum and its dependence on strain rate.
当金属受到极快速的压缩时，会产生一个冲击波，该冲击波在传播过程中会产生位错。冲击波会演变成一种典型的双波结构，其中弹性波先于塑性前沿。六十多年来人们一直知道，弹性波传播得越深入金属，其振幅衰减得就越厉害：这被称为“弹性前驱波的衰减”。弹性前驱波的振幅是一个动态屈服点，因为它标志着从弹性行为到塑性行为的转变。在本信函中，我们使用位错动力学的第一种方法来明确处理位错弹性场的时间依赖性，从而对这种衰减给出了完整解释。我们表明，弹性前驱波的衰减是弹性冲击波与在冲击波前沿形核的位错所发出的弹性波相互干涉的结果。我们的模拟定量地再现了最近关于铝中弹性前驱波衰减及其对应变速率依赖性的实验。
