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

University Of Iowa, Iowa City IA

Investigators

Abstract

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-moving primarily due to an inability to effectively model large material distortion and separation. There is also a fundamental difficulty associated with the numerical solution of strain localization 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 geotechnical materials, 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 large deformation analysis of geotechnical materials. 3. Develop an enhanced regularization method for analysis of material instability in strain localization. 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 an ongoing 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.