Degree Type

Thesis

Date of Award

2019

Degree Name

Master of Science

Department

Agricultural and Biosystems Engineering

Major

Agricultural and Biosystems Engineering

First Advisor

Mehari Z. Tekeste

Abstract

Multi-physics simulation of soil-to-tool interaction using a coupled Discrete Element Method (DEM) and Multibody dynamics (MBD) techniques can support the design of off-road equipment. Quantitative prediction of the soil reaction forces on the equipment is essential to provide a reliable simulation-based design. DEM is a computational method for simulating the dynamic behavior of granular materials. In the coupling interface, DEM gives a high fidelity prediction of the forces for soil-to-soil and soil-to-tool interaction, which can be used in the MBD simulation workflow. Two laboratory tests were used to capture the bulk material behavior: the angle of repose test for calibration of coefficients of static friction and rolling friction, and the cone penetrometer test to calibrate the soil shear modulus and normal and shear stiffnesses (related to the Hertz-Mindlin with bonding contact model). A simple pendulum test was developed to validate the DEM soil model in a soil-to-tool interaction application. The test was conducted in a soil bin filled loosely with loam soil at soil moisture content of 10% and initial soil bulk density of 1330 kg/m3. A cutting plate connected to the pendulum cut the soil at two levels of cutting depths (25 mm and 50 mm). The same application was simulated using the DEM simulation and DEM-MBD co-simulation. The horizontal and vertical soil cutting forces were compared between simulations and test. The magnitude of the maximum horizontal cutting forces for the experiment, DEM simulation, and DEM-MBD co-simulation were 73 N, 365 N, and 187 N, respectively for the 25 mm cutting depth and 108 N, 766 N, and 278 N, respectively for the 50 mm cutting depth. The DEM-MBD coupling improved the force prediction both for 25 mm and 50 mm cutting depths. It also closely predicted the trend in the increase in horizontal forces by cutting depth. The maximum horizontal soil cutting forces from experiment and DEM-MBD co-simulation increase by 48% and 49% by increasing the depth, respectively.

Copyright Owner

Sadaf Ghorbani

Language

en

File Format

application/pdf

File Size

83 pages

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