Publication news

Creating 3D models of tractor tire footprints using close-range digital photogrammetry

Amaneh E. Kenarsari, Stanley J. Vitton, John E. Beard,

Journal of Terramechanics, Volume 74, 2017, Pages 1-11, ISSN 0022-4898, http://dx.doi.org/10.1016/j.jterra.2017.06.001.
http://www.sciencedirect.com/science/article/pii/S0022489817301519


Abstract: Close-range digital photogrammetry is utilized to construct the 3D models of an agricultural tire footprint. These models were then analyzed to obtain the tire footprint depth, area and volume. The procedure of using the photogrammetry technique for developing 3D models of a tire footprint on soil as well as an assessment of the accuracy of the 3D models are discussed in this paper. Testing was conducted using a tractor tire in a large soil bin in a lab to generate a single tire footprint along with a rolling tire test to simulate a longer tire rut. Our experiments showed that the close-range digital photogrammetry provides an efficient and accurate method to assess the depth and volume of the tire footprint in soil.
Keywords: Photogrammetry; Tire footprint; 3D models; Large scale laboratory tests
 

Modeling of share/soil interaction of a horizontally reversible plow using computational fluid dynamics

Lin Zhu, Jia-Ru Ge, Xi Cheng, Shuang-Shuang Peng, Yin-Yin Qi, Shi-Wu Zhang, De-Quan Zhu

Journal of Terramechanics, Volume 72, 2017, Pages 1-8, ISSN 0022-4898

http://dx.doi.org/10.1016/j.jterra.2017.02.004.
http://www.sciencedirect.com/science/article/pii/S0022489817300393
Abstract: The horizontally reversible plow (HRP) is currently widely used instead of the regular mold-board plow due to its high operational performance. Soil pressure during HRP tillage generally has adverse effects on the plow surface, especially on either the plowshare or the plow-breast. This effect eventually shortens the tool’s service life. For this reason, this investigation used a three-dimensional (3D) computational fluid dynamics (CFD) approach to characterize the share/soil interaction and thus assess the effects of different tillage conditions on the interaction. To achieve this goal, a 3D model of the plowshare was first constructed in the commercial software SolidWorks, and soil from Xinjiang, China, was selected and subsequently characterized as a Bingham material based on rheological behaviors. Finally, 3D CFD predictions were performed using the control volume method in the commercial ANSYS code Fluent 14.0 in which the pressure distributions and patterns over the share surface were addressed under different tillage speeds in the range of 2–8ms−1 and at operational depths ranging from 0.1 to 0.3m. The results show that the maximum pressure appeared at the share-point zone of the plowshare and that the increase in soil pressure was accompanied by either higher tool speed or greater operational depth. The calculated results qualitatively agreed with the preliminary experimental evidence at the same settings according to scanning electron microscopy (SEM). Once again, the CFD-based dynamic analysis in this study is demonstrated to offer great potential for the in-depth study of soil-tool interactions by simulating realistic soil matter.
Keywords: Soil-share interaction; Computational fluid dynamics (CFD); Tillage speed; Operational depth; Horizontally reversible plow (HRP)
 

A coupled sliding and rolling friction model for DEM calibration

Zamir Syed, Mehari Tekeste, David White

Journal of Terramechanics, Volume 72, 2017, Pages 9-20, ISSN 0022-4898

http://dx.doi.org/10.1016/j.jterra.2017.03.003.
http://www.sciencedirect.com/science/article/pii/S0022489817300721
Abstract: The accuracy of dense Discrete Element Method (DEM) simulations is sensitive to initial density, contact orientation, particle size and shape, and interparticle interaction parameters including contact stiffness, cohesion, coefficients of friction, and coefficients of restitution. Although studies have characterized the effects of individual particle interaction parameters on mechanical responses of loaded granular material, research combining DEM parameters for calibration is scarce. Robust DEM calibration methodology combining sliding and rolling friction coefficients was developed and validated to predict bulk residual soil strength of initially dense DEM particle assemblies.
Keywords: Coupled sliding and rolling friction coefficients; Discrete element method; Soil
 

Application of the FEM/DEM and alternately moving road method to the simulation of tire-sand interactions

Chun-Lai Zhao, Meng-Yan Zang

Journal of Terramechanics, Volume 72, 2017, Pages 27-38, ISSN 0022-4898,

http://dx.doi.org/10.1016/j.jterra.2017.04.001.  
http://www.sciencedirect.com/science/article/pii/S002248981730085X
Abstract: The three-dimensional finite-discrete element method (FEM/DEM) is applied to the simulation of tire-sand interactions, where the tire is discretized into hexahedron finite elements and sand is modeled by using the discrete element method. The feasibility and effectiveness of the method are proven by comparing the simulation results with the current reported results. Since long test roads are usually required for investigating tire running behaviors, which lead to large-scale simulation models and time consuming problems, the alternately moving road method is proposed to handle this problem. It can simulate tire running behaviors on an arbitrary length sand road with a constant road length value. The numerical model of a lug tire running on a bisectional road with fine and coarse sand is established to verify the feasibility of the method.


Keywords: Finite element method; Discrete element method; Terramechanics; Computational mechanics; Tire-sand interactions
 

Calculating fractal parameters from low-resolution terrain profiles

Christopher Goodin, Maria Stevens, Francisco J. Villafañe Rosa, Burney McKinley, Burhman Q. Gates, Phillip J. Durst, George L. Mason, Alex Baylot

 Journal of Terramechanics, Volume 72, 2017, Pages 21-26, ISSN 0022-4898, http://dx.doi.org/10.1016/j.jterra.2017.03.002.
http://www.sciencedirect.com/science/article/pii/S0022489817300642
Abstract: Driver comfort on rough terrain is an important factor in the off-road performance of wheeled and tracked ground vehicles. The roughness of a terrain has typically been quantified by the U.S. Army as the root-mean-square elevation deviation (RMS) of the terrain profile. Although RMS is an important input into many mobility calculations, it is not scale invariant, making it difficult to estimate RMS from low resolution terrain profiles. Fractal parameters are another measure of roughness that are scale invariant, making them a convenient proxy for RMS. While previous work found an empirical relationship between fractal dimension and RMS, this work will show that, by including the cutoff length, an analytic relationship between fractal properties and RMS can be employed. The relationship has no free parameters and agrees very well with experimental data - thus providing a powerful predictive tool for future analyses and a reliable way to calculate surface roughness from low-resolution terrain data in a way that is scale invariant. In addition, we show that this method applies to both man-made ride courses and natural terrain profiles.
Keywords: Fractal dimension; RMS; Surface roughness
 

A high-fidelity approach for vehicle mobility simulation: Nonlinear finite element tires operating on granular material

Antonio Recuero, Radu Serban, Bryan Peterson, Hiroyuki Sugiyama, Paramsothy Jayakumar, Dan Negrut  

Journal of Terramechanics, Volume 72, August 2017, Pages 39-54, ISSN 0022-4898, https://doi.org/10.1016/j.jterra.2017.04.002.
http://www.sciencedirect.com/science/article/pii/S0022489816301173  
Abstract:  
Assessing the mobility of off-road vehicles is a complex task that most often falls back on semi-empirical approaches to quantifying the vehicle–terrain interaction. Herein, we concentrate on physics-based methodologies for wheeled vehicle mobility that factor in both tire flexibility and terrain deformation within a fully three-dimensional multibody system approach. We represent the tire based on the absolute nodal coordinate formulation (ANCF), a nonlinear finite element approach that captures multi-layered, orthotropic shell elements constrained to the wheel rim. The soil is modeled as a collection of discrete elements that interact through contact, friction, and cohesive forces. The resulting vehicle/tire/terrain interaction problem has several millions of degrees of freedom and is solved in an explicit co-simulation framework, built upon and now available in the open-source multi-physics package Chrono. The co-simulation infrastructure is developed using a Message Passing Interface (MPI) layer for inter-system communication and synchronization, with additional parallelism leveraged through a shared-memory paradigm. The formulation and software framework presented in this investigation are proposed for the analysis of the dynamics of off-road wheeled vehicle mobility. Its application is demonstrated by numerical sensitivity studies on available drawbar pull, terrain resistance, and sinkage with respect to parameters such as tire inflation pressure and soil cohesion. The influence of a rigid tire assumption on mobility is also discussed.  
Keywords: Mobility; Off-road vehicle dynamics; Nonlinear finite element; ANCF; Discrete element method; Chrono; Co-simulation; High-performance computing

 

Application of the FEM/DEM and alternately moving road method to the simulation of tire-sand interactions

Chun-Lai Zhao, Meng-Yan Zang
Journal of Terramechanics, Volume 72, August 2017, Pages 27-38, ISSN 0022-4898, https://doi.org/10.1016/j.jterra.2017.04.001.
http://www.sciencedirect.com/science/article/pii/S002248981730085X

Abstract: 
The three-dimensional finite-discrete element method (FEM/DEM) is applied to the simulation of tire-sand interactions, where the tire is discretized into hexahedron finite elements and sand is modeled by using the discrete element method. The feasibility and effectiveness of the method are proven by comparing the simulation results with the current reported results. Since long test roads are usually required for investigating tire running behaviors, which lead to large-scale simulation models and time consuming problems, the alternately moving road method is proposed to handle this problem. It can simulate tire running behaviors on an arbitrary length sand road with a constant road length value. The numerical model of a lug tire running on a bisectional road with fine and coarse sand is established to verify the feasibility of the method. 

Keywords: Finite element method; Discrete element method; Terramechanics; Computational mechanics; Tire-sand interactions

 

A coupled sliding and rolling friction model for DEM calibration

Zamir Syed, Mehari Tekeste, David White   
Journal of Terramechanics, Volume 72, August 2017, Pages 9-20, ISSN 0022-4898, https://doi.org/10.1016/j.jterra.2017.03.003.
http://www.sciencedirect.com/science/article/pii/S0022489817300721

Abstract:
The accuracy of dense Discrete Element Method (DEM) simulations is sensitive to initial density, contact orientation, particle size and shape, and interparticle interaction parameters including contact stiffness, cohesion, coefficients of friction, and coefficients of restitution. Although studies have characterized the effects of individual particle interaction parameters on mechanical responses of loaded granular material, research combining DEM parameters for calibration is scarce. Robust DEM calibration methodology combining sliding and rolling friction coefficients was developed and validated to predict bulk residual soil strength of initially dense DEM particle assemblies.

Keywords: Coupled sliding and rolling friction coefficients; Discrete element method; Soil

Calculating fractal parameters from low-resolution terrain profiles

Christopher Goodin, Maria Stevens, Francisco J. Villafañe Rosa, Burney McKinley, Burhman Q. Gates, Phillip J. Durst, George L. Mason, Alex Baylot

Journal of Terramechanics, Volume 72, August 2017, Pages 21-26, ISSN 0022-4898, http://doi.org/10.1016/j.jterra.2017.03.002.
http://www.sciencedirect.com/science/article/pii/S0022489817300642

Abstract: 
Driver comfort on rough terrain is an important factor in the off-road performance of wheeled and tracked ground vehicles. The roughness of a terrain has typically been quantified by the U.S. Army as the root-mean-square elevation deviation (RMS) of the terrain profile. Although RMS is an important input into many mobility calculations, it is not scale invariant, making it difficult to estimate RMS from low resolution terrain profiles. Fractal parameters are another measure of roughness that are scale invariant, making them a convenient proxy for RMS. While previous work found an empirical relationship between fractal dimension and RMS, this work will show that, by including the cutoff length, an analytic relationship between fractal properties and RMS can be employed. The relationship has no free parameters and agrees very well with experimental data - thus providing a powerful predictive tool for future analyses and a reliable way to calculate surface roughness from low-resolution terrain data in a way that is scale invariant. In addition, we show that this method applies to both man-made ride courses and natural terrain profiles.  
Keywords: Fractal dimension; RMS; Surface roughness