Adaptive Multiple-Scale Meshfree Method for Geo-Mechanics and Earth-Moving Simulation

传统的有限元方法在分析大变形、高梯度、材料分离和多尺度现象等问题时表现出许多缺点。 这些困难部分是由于有限元网格的规则性要求。 在农业和建筑业中，非常需要高生产率的运土设备的设计。 理解挖掘、运输和倾倒过程中的土壤运动对于设计高生产率的土方设备至关重要。 土体在移动过程中表现出过度的塑性变形和破坏机制。 有限元方法还没有成功地应用于分析土方工程，主要是由于不能有效地模拟大的材料变形和分离，还有一个基本的困难与应变局部化的数值解，经常存在于分析土方工程过程. 基于网格的数值方法（例如有限元方法）引入长度尺度，即，在分叉问题中的网格尺寸。因此，数值解可以敏感地依赖于网格尺寸。 岩土材料中剪切带形成的多尺度特性也给传统的有限元方法增加了相当大的复杂性，本研究的目的是发展一种实用的模拟方法，能够预测岩土材料中的大变形、剪切带形成、损伤演化和材料分离，并应用于土方工程过程。 特别强调的是，将给予发展的自适应多尺度无网格方法，允许一个互动的和连续的H-和P-模型的土壤运动的模拟细化。 土体局部剪切带和损伤机制对土体整体运动具有重要影响。 最终的目标是捕捉到嵌入在整体土壤响应中的细尺度局部剪切带和剪切/拉伸破坏机制。 与卡特彼勒的合作将使研究工作的实验验证的本构模型和拟议的无网格方法。 本研究的主要目的是：1.基于PI在岩土材料无网格方法研究方面的进展，发展了无网格多尺度公式和h-和p-自适应方法，并将其应用于土体运动模拟.发展稳定协调节点积分用于岩土材料的加速无网格大变形分析.发展了一种改进的正则化方法用于应变局部化中材料失稳的分析.与Caterpillar合作，通过与Caterpillar提供的实验数据进行比较，验证所采用的材料模型和所提出的无网格方法的性能。卡特彼勒承诺帮助验证土壤本构和损伤模型以及无网格方法，这将确保拟议的无网格方法在分析工业土方工程问题时的实际应用的适用性。

Conventional finite element methods exhibit a number of shortcomings in analyzing problems that involve large deformation, high gradient, material separation, and multiple-scale phenomena. These difficulties are partially due to the regularity requirement of the finite element mesh. In agricultural and construction industries, designs for high productivity earth-moving equipment are highly desirable. The understanding of soil motion during excavation, hauling, and dumping is critical to the design of high productivity earth-moving equipment. Soil motion during the earth-moving process exhibits excessive plastic deformation in conjunction with failure mechanisms. Finite element methods have not been successfully applied to the analysis of earth-movingprimarily due to an inability to effectively model large material distortion and separation.There is also a fundamental difficulty associated with the numerical solution of strainlocalization that often exists in analyzing earth-moving processes. Grid-based numerical methods such as finite element methods introduce a length scale, i.e., the mesh size, in a bifurcation problem. As a result, the numerical solution can be sensitively dependent on the mesh size. The multiple-scale nature of shear-band formation in geotechnical materials also adds considerable complication to conventional finite element approaches.The objective of this research is to develop a practical simulation method capable of predicting large deformation, shear-band formation, damage evolution, and material separation in geotechnical materials with applications to earth-moving processes. Special emphasis will be given to the development of an adaptive multiple-scale meshfree method that allows an interactive and continuous h- and p- model refinement in the simulation of soil motion. The local shear-band and damage mechanisms are critical to overall soil motion in earth moving processes. The ultimate goal is to capture the fine-scale local shear-band and shear/tensile failure mechanisms embedded in the overall soil response. A collaboration with Caterpillar will enable research effort on experimental validation of the employed constitutive model and the proposed meshfree methods. The major objectives of this research are: 1. Based on the PI's previous research progress on meshfree methods for geotechnicalmaterials, develop meshfree multiple-scale formulation and h- and p- adaptivity methods for application to earth-moving simulation.2. Develop a stabilized conforming nodal integration for accelerated meshfree largedeformation analysis of geotechnical materials.3. Develop an enhanced regularization method for analysis of material instability in strainlocalization.4. Collaborate with Caterpillar to verify the performance of the employed material models and the proposed meshfree methods by comparison with experimental data provided by Caterpillar.This proposed multiple-scale adaptive meshfree method extends the development from anongoing collaboration with Caterpillar Inc. The commitment from Caterpillar to aid in validation of the soil constitutive and damage models and meshfree methods will assure the applicability of the proposed meshfree methods for practical use in analyzing industrial earth-moving problems.