用神经网络求解微结构材料变形,同时验证解的物理稳定性。
Physics-Consistent Neural Networks for Learning Deformation and Director Fields in Microstructured Media with Loss-Based Validation Criteria
- 神经网络直接最小化总势能,满足框架不变性和方向场单位长度约束。
- 提出能量稳定性的必要条件,用于判断神经网络输出是否为物理可接受解。
- 适合研究具有微观结构的智能材料或弹性力学问题的研究者。
本文基于单向量构型的柯西弹性理论,研究具有微观结构固体的力学行为,该理论能捕捉形变与取向场间的耦合关系。为计算此类介质的平衡构型,提出两种互补方法:基于变分原理的有限元法和直接最小化总势能的神经网络求解器。神经架构尊重理论的基本运动学结构,包括能量的框架不变性、方向场的单位长度约束,并通过独立网络表示形变与方向场以保持其变分设置下的运动学独立性。除了满足平衡律外,物理可接受解还需对应于稳定的能量极小值。为此,推导了柯西模型的拟凸性、一阶凸性及勒让德-哈达玛不等式,并将其转化为适用于评估神经网络预测的形式。这些必要稳定性条件构成物理驱动的验证框架:违反这些条件的网络输出无法对应稳定能量极小值,因而可被拒绝。由此实现经典变分稳定性理论与现代机器学习求解器的融合,建立了一种不仅学习平衡解,还评估其能量一致性的计算流程。
原文摘要 · Abstract (English)
In this work, we study the mechanical behavior of solids with microstructure using the framework of Cosserat elasticity with a single unit director. This formulation captures the coupling between deformation and orientational fields that arises in many structured materials. To compute equilibrium configurations of such media, we develop two complementary computational approaches: a finite element formulation based on variational principles and a neural network-based solver that directly minimizes the total potential energy. The neural architecture is constructed to respect the fundamental kinematic structure of the theory. In particular, it enforces frame invariance of the energy, satisfies the unit-length constraint on the director field, and represents deformation and director fields through separate networks to preserve their kinematic independence in the variational setting. Beyond satisfying balance laws, however, physically admissible solutions must also correspond to stable energy minimizers. To assess this requirement, we derive the quasiconvexity condition, rank-one convexity condition, and the Legendre-Hadamard inequalities for the Cosserat model and formulate them in a manner suitable for evaluating neural network predictions. These necessary stability conditions provide a physics-based validation framework: network outputs that violate these necessary conditions cannot correspond to stable energy minimizers and can therefore be rejected. In this way, we integrate classical variational stability theory with modern machine-learning solvers, establishing a computational workflow in which equilibrium solutions are not only learned but also assessed for energetic consistency.
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