基于CLoE亚塑性模型的密砂循环荷载下力学行为模拟

亚塑性模型为模拟颗粒材料的非线性力学行为提供了一条新途径，特别是CLoE亚塑性模型在模拟应变局部化时具有一定的优势。然而该模型在模拟小幅应力-应变循环时表现出一定的锯齿效应。为了克服该效应，基于颗粒间应变张量的概念发展了修正的CLoE亚塑性模型以正确模拟循环荷载下密砂的力学行为。此外，为保证单调荷载作用下修正模型与原模型预测结果的一致性，改进了颗粒间应变率及颗粒间最大应变的定义。数值算例表明:（1）修正模型保留了克服锯齿效应的优点。（2）修正模型能够反映不同振幅条件下的卸载刚度。（3）在大振幅循环条件下，滞回圈的面积随着循环次数增加而增大。（4）修正模型能够保证单调加载条件下所得结果与原模型的一致性。（5）修正模型可以反映材料的疲劳破坏机制。

Modelling behavior of dense sand subjected to cyclic loading based on CLoE hypoplastic model

The theory of hypoplasticity provides an effective mean for modeling the nonlinear behavior of granular materials. In particular the CLoE hypoplastic model has salient advantages in modeling the strain localization problems. In simulating the cyclic stress-strain loops with small amplitude, however, the hypoplastic model shows the ratcheting effect. To resolve this issue, the intergranular strain tensor is incorporated into the CLoE hypoplastic model so that it can effectively describe the behavior of dense sand under cyclic loading. In addition, to reserve the consistency of the modified model in describing the sand behavior under monotonic loading conditions, the definitions of intergranular strain rate and the maximum intergranular strain are improved. The numerical results show that (1) the modified model reserves the advantage of overcoming ratcheting effect; (2) the modified model can account for the unloading stiffness of different cyclic amplitudes; (3) for large cyclic amplitudes, the area of the cyclic loop increases with cyclic number; (4) the consistency of the modified CLoE model and CLoE model can also be guaranteed under the same monotonous loading condition; (5) the modified model well represents the mechanism of the fatigue-induced failure of materials.