基于三维弹塑性损伤模型的木材非线性分析

为预测木材复杂的受力行为，在弹塑性理论和连续介质损伤力学的框架内建立了木材三维弹塑性损伤本构模型。采用Hill屈服准则和Voce强化模型描述木材受压硬化行为；通过修正后的Hashin破坏准则和指数型损伤演化模型控制木材受拉、受剪的损伤演化过程。基于应变增量法求解本构模型的数值解，并采用Newton-Raphson迭代法求解塑性应变。通过编写用户自定义子程序（UMAT）将本构模型嵌入商业有限元软件ABAQUS，并根据试验结果对本构模型进行了验证。针对木材顺纹和横纹受压试验的数值模拟结果表明，该模型可以有效地描述木材的受压非线性硬化行为。针对木材斜纹受拉试验的数值模拟结果表明破坏准则可以较为准确地识别木材在横纹拉应力和顺纹剪应力作用下的破坏模式，损伤演化模型可以合理地控制木材的损伤演化过程。

Nonlinear analysis of wood based on three-dimensional combined elastic-plastic and damage model

In order to predict the complex mechanical behavior of wood, a three dimensional constitutive model was established within the framework of elastic-plastic theory and continuum damage mechanics. Hill yielding criterion and Voce hardening model were selected to describe the hardening behavior of wood under compression. The modified Hashin criterion and exponential damage evolution model were adopted to describe the damage evolution of wood under tension and/or shear. A strain increment based algorithm was developed for the numerical solution of the constitutive model, and the Newton-Raphson iterative method was used to calculate the plastic strain. The constitutive model was implemented into the commercial finite element software ABAQUS via a user-defined subroutine (UMAT), and was validated with test results. The simulation results of wood under longitudinal and radial compression indicated that the constitutive model can effectively describe the hardening behavior of wood under compression. It was also found that the failure criterion can accurately capture the failure modes of wood subjected to combined tension stress perpendicular-to-wood-grain direction and longitudinal stress, and the damage evolution model can reasonably track the damage evolution of wood.