基于能量的弹塑性损伤实用本构模型

建立一个实用的弹塑性损伤本构模型。在有效应力空间采用经验公式计算塑性变形，能将模型塑性部分与损伤部分解耦，降低模型的数值处理复杂性，同时大大简化模型塑性应变的计算。结合不可逆热力学理论，基于损伤能量释放率建立损伤准则，损伤能量释放率由修正后的弹性Helmholtz自由能导出，模型中将弹性Helmholtz自由能分解为应力球量部分和应力偏量部分，将其应力球量部分产生的损伤取为零，同时根据应力状态引入折减系数对其应力偏量部分进行修正，使得模型能较为准确的模拟混凝土材料在双轴加载下的本构行为。将应力张量谱分解为正、负两部分以分别定义材料受拉、受压损伤演化，并采用受拉损伤变量、受压损伤变量分别模拟混凝土材料在拉、压加载下的本构特性。引入一个加权损伤变量使得模型能较准确的反映混凝土材料的“拉-压软化效应”。最后该文给出初步试验验证，证明了该文模型的有效性。

A PRACTICAL ELASTIC PLASTIC DAMAGE CONSTITUTIVE MODEL BASED ON ENERGY

In this article, an energy based practical elastic plastic damage constitutive model is established. The effective stress space concept is adopted which can decouple the damage and plastic processes. Empirical formula is used to determine the plastic deformations in effective stress space which can improve the calculation efficiency. Within a framework of irreversible thermodynamics, the damage criteria are based on elastic damage energy release rate which is derived from the modified elastic Helmholtz free energy. In order to improve the accuracy of the model under biaxial loading, the Helmholtz free energy is decomposed into hydrostatic and deviatoric stress components in which the damage evolution produced by hydrostatic stress component is neglected. Thus, the calculation’s efficiency is improved to be free of iteration and the deviatoric stress component is amended according to stress state. The stress tensor is spectral decomposed into tensile and compressive components in order to reflect different damage evolutions, and a tensile and a compressive damage variables are used to simulate different responses of the concrete under tension and compression. Finally,the proposed model is validated by several numerical simulations.