基于人工神经网络的颗粒材料本构关系及边值问题研究

Study on Constitutive Relations and Boundary Value Problems of Granular Materials Based on Artificial Neural Networks

颗粒材料被广泛运用于工程实践中,通过数值模拟解决颗粒材料有关的边值问题,对于指导工程实践具有重要意义.通过应用人工神经网络算法,将基于离散颗粒模型的离散单元法与基于连续介质模型的有限单元法有机结合以求解颗粒材料边值问题,形成了一套新的、完整的模型及解决方案,即细观模型离线计算的细-宏观两尺度模型及求解系统.具体为:先基于离散单元法获取颗粒材料的主应力、主应变以及对应的应力-应变矩阵等数据;再将获取的数据利用人工神经网络算法构建在主空间上描述颗粒材料本构关系的人工神经网络模型;最后,通过用户自定义材料子程序UMAT将人工神经网络模型导入ABAQUS中求解颗粒材料边值问题.通过平板受压以及边坡稳定性数值试验,并与经典弹塑性模型求解结果进行对比,表明了训练后的人工神经网络模型能够有效地反映颗粒材料的本构关系,并能够运用于实践求解边值问题,验证了该求解方案的可行性.

Granular materials are widely used in engineering practice,where the numerical simulation of boundary value problems related to granular materials is of great significance.By the artificial neural network algorithm,the discrete element method based on discrete particle models and the finite element method based on continuous models were organically combined to solve the boundary value problems of granular materials.A new and complete model and the solution were formed,namely,the micro-macroscopic 2-scale model and its solution system for offline calculation of the meso model.Specifically,the principal stress,the principal strain,and the corresponding stress-strain matrix of a granular material were first obtained based on the discrete element method.Then an artificial neural network model was built in the main space to describe the constitutive relationship of the granular material by an artificial neural network algorithm.Finally,the artificial neural network model was imported into ABAQUS to solve the boundary value problem of the granular material with the user-defined material subroutine UMAT.Through the numerical tests of plate compression and slope stability,and the comparison with the solution results of the classical elastoplastic model,it is seen that the trained artificial neural network model can effectively reflect the constitutive relationship of granular materials,and can be used in practice to solve boundary value problems.The results show the feasibility of the solution scheme.