Modeling soil-to-bulldozer blade interaction using the discrete element method (DEM)

Authors: TEKESTE, MEHARI - Iowa State University; Way, Thomas - Tom; SYED, ZAMIR - Iowa State University; SCHAFER, ROBERT - Retired ARS Employee

Submitted to: Terramechanics Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2020
Publication Date: 1/20/2020
Citation: Tekeste, M., Way, T.R., Syed, Z., Schafer, R. 2020. Modeling soil-to-bulldozer blade interaction using the discrete element method (DEM). Terramechanics Journal. 88:41-52. https://doi.org/10.1016/j.jterra.2019.12.003.
DOI: https://doi.org/10.1016/j.jterra.2019.12.003

Interpretive Summary: Use of computers to simulate interactions of agricultural and other equipment with soil is important in reducing the time and cost of equipment analysis and development, for manufacturers and researchers. The Discrete Element Method (DEM) is a computer simulation method which simulates a large number of particles and their interactions with solid surfaces which contain them or pass between them. DEM was used in this project to simulate four scaled-down sizes of a bulldozer blade (24%, 14%, 10%, and 5% of full-scale blade dimensions) pushing sandy loam soil. The simulations predicted the horizontal forces applied by the blades to the soil, and these results were compared with horizontal forces applied by actual blades to actual sandy loam soil. The DEM simulation results were in strong agreement with the actual blade and soil results, as the linear regression of soil horizontal force predicted by DEM with the actual force, had R^2 = 0.9965 and a slope of 0.9634. These results are expected to be helpful in improving the application of DEM to soil-machine interactions, and in promoting the accuracy and usefulness of simulation for equipment development.

Technical Abstract: Modeling soil-to-bulldozer blade interaction using the Discrete Element Method (DEM) technique has the potential to accelerate simulation-based design and performance analysis of earthmoving equipment. DEM has been shown to be a powerful numerical technique to model dynamic soil behaviors as tools interact with soil. Limited studies have been conducted to establish scaling relationships of soil reaction forces on blades and length scales of bulldozer blades using the DEM technique. With a DEM-based similitude scaling law, performance of industry-scale blades can be predicted with reduced simulation efforts. Developing a DEM soil model to match laboratory soil bulk response and validating the soil-to-blade simulation using physical experiments requires a rigorous material properties calibration approach. The objectives of the study were to develop a DEM soil model for Norfolk sandy loam soil, establish a scaled relationship of soil reaction forces to bulldozer blade length scales (n = 0.24, n = 0.14, n = 0.10, and n =0.05, so these were four scaled-down sizes of a bulldozer blade, with 24%, 14%, 10%, and 5% of full-scale blade dimensions), and validate the DEM-predicted soil reaction forces to the Norfolk sandy loam soil bin data. Using 3D-scanned and reconstructed DEM soil aggregate shapes and Design of Experiment, we used DEM to predict soil cone penetration testing and mean values of soil cone index for Norfolk sandy loam soil. A DEM soil model, which was calibrated to soil cone penetration testing, was used to simulate the soil-to-bulldozer blade interaction. A power fit best approximated the relationship between the DEM-predicted soil horizontal forces and bulldozer blade length scale (R^2 = 0.9976). DEM prediction of soil horizontal forces on bulldozer blades explained the Norfolk sandy loam soil bin data with a linear regression fit (R^2 = 0.9965 and slope = 0.9634).