Paper presented at the 16th European-African Regional Conference of the ISTVS
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Title: Numerical modeling of a tire on undrained saturated clay using FEM, ALE, and SPH
Authors: Varsha S Swamy, Rashna Pandit, Alba Yerro, Corina Sandu, Denise M. Rizzo, Katherine Sebeck, and David Gorsich
Abstract: Modeling and performance prediction of tires on wet, plastic, cohesive soils is a challenge. Unlike dry soils, in wet soils the undrained shear strength is lesser. The worst scenario is when the soil is fully saturated. This work aims at modeling highly deformable saturated clay and predicting the performance of pneumatic tires on such terrain. The short-term effect on the soil due to single tire pass is of focus. First, the modeling and validation of the soil material model is discussed. Dealing with saturated soils, it is important to understand the effect of the water in the pores. The total stresses acting on the soil can be divided into the stress on the soil skeleton (effective stresses) and water (pore water pressure). It is the effective stresses that determine the soil failure. Hence, material models are calibrated and validated from geotechnical experiments using two different frameworks: (a) total stress (b) effective stress. In the total stress analysis, commonly found in the literature, soil and water are modeled as one medium. In the effective stress analysis, the model represents only the soil skeleton and it is hydro-mechanically coupled to produce a larger range of initial stress states. The performance of the tire using different numerical techniques including FEM, Arbitrary Lagrangian Eulerian (ALE), and Smoothed Particle Hydrodynamics (SPH) are compared using these models. Finally, it is concluded that with the effective stress model, there is accumulation of excessive pore water pressure, which may affect the second pass later. In addition, the FEM model fails to give acceptable solutions for higher normal loads and slip ratios as a result of excessive deformation. ALE and SPH give more stable solutions when large deformations develop.
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