Buildup of anamnesis and swept out of memory under coupling of monotonic and cyclic loading

本项目的目的是发展一种耦合循环显式本构模型与非线性单调材料模型并行的方法。单调模式和循环模式所使用的历史变量的演化应该用这种耦合来描述。这些演化方程应该允许材料记忆的积累（记忆）和/或其退化取决于加载条件。土的力学行为受加载历史（即应力/应变路径依赖）的强烈影响。土的内部结构随荷载的变化而变化，每次荷载的变化都会引起土骨架中力链的重组。这种重组可以看作是某种记忆的积累或退化。在本研究项目的上下文中，耦合模型应该捕捉到这种记忆的演化规律。通过耦合实例，将欠塑性模型和HCA模型合并为一个单一的本构方程，在该方程中可以同时处理单调和循环荷载。除了单调和循环荷载的同时（并行）作用外，这种耦合还可以描述单调和循环荷载的顺序（串行）交替。通过单元试验，可以研究不同预压条件（单调或循环）对历史变量演变的影响，并对所需参数进行校准。这种耦合的预测和解释潜力，以及其数值实现的鲁棒性，应该在一个示例性边值问题的有限元模拟的帮助下得到证明。

The aim of this project is to develop a method to couple a cyclic explicit constitutive model inparallel with a non-linear monotonic material model. The evolution of the historiotropic state variables used by both the monotonic and the cyclic models should be described by this coupling. These evolution equations should allow the buildup of material memory (anamnesis) and/or its degradation depending on the loading conditions. The mechanical soil behavior is strongly influenced by the loading history (i.e. stress/strain path dependency). The soil adapts its internal structure to the applied loads and each load change causes a reorganization of force chains in the soil skeleton. This reorganization can be regarded as some kind of buildup or degradation of memory. The evolution laws of this memory should be captured by the coupling model in the context of this research project. By way of example of the coupling, the hypoplastic and the HCA models are combined into a single constitutive equation, in which monotonic and cyclic loads can be simultaneously treated. In addition to the simultaneous (parallel) application of monotonic and cyclic loads, this coupling can describe the sequential (serial) alternation of monotonic and cyclic loads. By means of element tests the influence of different preloading (monotonic or cyclic) conditions on the evolution of the historiotropic variables can be studied and the required parameters calibrated. The predictive and explanatory potential of this coupling as well as the robustness of its numerical implementation should be demonstrated with the help of a finite element simulation of an exemplary boundary value problem.