Rottler J, Robbins M O
Department of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2001 Nov;64(5 Pt 1):051801. doi: 10.1103/PhysRevE.64.051801. Epub 2001 Oct 18.
Shear yielding of glassy polymers is usually described in terms of the pressure-dependent Tresca or von Mises yield criteria. We test these criteria against molecular dynamics simulations of deformation in amorphous polymer glasses under triaxial loading conditions that are difficult to realize in experiments. Difficulties and ambiguities in extending several standard definitions of the yield point to triaxial loads are described. Two definitions, the maximum and offset octahedral stresses, are then used to evaluate the yield stress for a wide range of model parameters. In all cases, the onset of shear is consistent with the pressure-modified von Mises criterion, and the pressure coefficient is nearly independent of many parameters. Under triaxial tensile loading, the mode of failure changes to cavitation, and the von Mises criterion no longer applies.
玻璃态聚合物的剪切屈服通常根据与压力相关的特雷斯卡屈服准则或冯·米塞斯屈服准则来描述。我们将这些准则与非晶态聚合物玻璃在三轴加载条件下变形的分子动力学模拟结果进行对比，而这种三轴加载条件在实验中难以实现。文中描述了将屈服点的几个标准定义扩展到三轴载荷时所面临的困难和模糊性。随后使用两个定义，即最大八面体应力和偏移八面体应力，来评估一系列模型参数下的屈服应力。在所有情况下，剪切的起始都与压力修正后的冯·米塞斯准则一致，并且压力系数几乎与许多参数无关。在三轴拉伸载荷下，失效模式转变为空化，此时冯·米塞斯准则不再适用。
