用深度瑞兹方法求解非线性材料均匀化中的参数化细观问题,实现高效可微的宏观响应计算。
Nonlinear elliptic homogenization with the parametric Deep Ritz method

- 基于变分结构,用神经网络同时求解多状态下的细观问题
- 相比传统FE²方法,宏观求解速度提升显著,且结果连续可微
- 适合需要快速、可微材料响应的多尺度仿真场景
椭圆型均匀化用于确定具有微小尺度特征材料的粗粒度属性。当这些微小特征呈现快速周期性波动时,基于均匀化本构关系的解与真实异质材料解高度吻合。该均匀化行为通过细观问题求解,其中细观单元定义为波动材料的一个周期。在线性椭圆偏微分方程中,均匀化本构关系由常数张量定义;但在非线性问题中,均匀化响应依赖于宏观状态和/或其梯度,因此需求解参数化细观问题。在数值求解中,若能获得细观解的可微表示,将有助于宏观数值求解中牛顿迭代所需的导数计算。本文采用深度瑞兹方法求解非线性均匀化中产生的参数化细观问题。首先利用细观问题的变分结构,然后以神经网络离散空间与宏观状态的依赖关系。通过强加边界条件,使用参数化深度瑞兹方法在多个宏观状态上同时求解细观问题。结果显示该方法精度高、效率优,并提供对宏观状态和梯度的连续可微响应表示。进一步表明,相较于传统FE²方案,本方法显著加速了宏观尺度求解过程。
原文摘要 · Abstract (English)
Elliptic homogenization is used to determine coarse-grained properties of materials with features on small scales. When these small scale features have rapid, periodic fluctuations, the solution field corresponding to a homogenized constitutive relation closely resembles the true solution based on the heterogeneous material. This homogenized behavior of the material is computed from a cell problem, where a cell is defined to be one period of the fluctuating material. In the context of linear elliptic partial differential equations, the homogenized constitutive relation is defined simply by a constant coefficient tensor, but for nonlinear problems, the homogenized response depends on the macroscopic state and/or its gradient, thus requiring solutions to parametric cell problems. When computing a numerical solution with the homogenized constitutive relation, it is useful to have a differentiable representation of the solution to the cell problem, as derivatives of the homogenized constitutive relation are required in Newton iterations for the macroscopic state field. In this work, we use the Deep Ritz method to solve the parametric cell problems that arise from nonlinear homogenization. First, we exploit the variational structure of the cell problem, then we discretize the dependence of the cell response on both space and the macroscopic state with a neural network. Enforcing boundary conditions on the cell response strongly, we next use the parametric Deep Ritz method to simultaneously solve the cell problem over a range of macroscopic states. We show that this method is accurate, efficient, and offers a continuous and differentiable representation of the cell response over the macroscopic state and gradient. We then show that our parametric representation of the cell response significantly expedites macroscale solutions when compared to a traditional $\text{FE}^2$ scheme.
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