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,

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
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)

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,
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 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,  
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


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,

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 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,

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


DEM simulation of soil-tool interaction under extraterrestrial environmental effects

Mingjing Jiang, Banglu Xi, Marcos Arroyo, Alfonso Rodriguez-Dono, Journal of Terramechanics, Volume 71, June 2017, Pages 1-13, ISSN 0022-4898,


In contrast to terrestrial environment, the harsh lunar environment conditions include lower gravity acceleration, ultra-high vacuum and high (low) temperature in the daytime (night-time). This paper focuses on the effects of those mentioned features on soil cutting tests, a simplified excavation test, to reduce the risk of lunar excavation missions. Soil behavior and blade performance were analyzed under different environmental conditions. The results show that: (1) the cutting resistance and the energy consumption increase linearly with the gravity. The bending moment has a bigger increasing rate in low gravity fields due to a decreasing moment arm; (2) the cutting resistance, energy consumption and bending moment increase significantly because of the raised soil strength on the lunar environment, especially in low gravity fields. Under the lunar environment, the proportions of cutting resistance, bending moment and energy consumption due to the effect of the van der Waals forces are significant. Thus, they should be taken into consideration when planning excavations on the Moon. Therefore, considering that the maximum frictional force between the excavator and the lunar surface is proportional to the gravity acceleration, the same excavator that works efficiently on the Earth may not be able to work properly on the Moon.

Keywords: Lunar regolith; Distinct Element Method; Soil cutting test; Cutting resistance; Van der Waals force; Gravity effect


Terrain classification using intelligent tire

Seyedmeysam Khaleghian, Saied Taheri, Journal of Terramechanics, Volume 71, June 2017, Pages 15-24, ISSN 0022-4898,


A wheeled ground robot was designed and built for better understanding of the challenges involved in utilization of accelerometer-based intelligent tires for mobility improvements. Since robot traction forces depend on the surface type and the friction associated with the tire-road interaction, the measured acceleration signals were used for terrain classification and surface characterization. To accomplish this, the robot was instrumented with appropriate sensors (a tri-axial accelerometer attached to the tire innerliner, a single axis accelerometer attached to the robot chassis and wheel speed sensors) and a data acquisition system. Wheel slip was measured accurately using encoders attached to driven and non-driven wheels. A fuzzy logic algorithm was developed and used for terrain classification. This algorithm uses the power of the acceleration signal and wheel slip ratio as inputs and classifies all different surfaces into four main categories; asphalt, concrete, grass, and sand. The performance of the algorithm was evaluated using experimental data and good agreements were observed between the surface types and estimated ones.

Keywords: Wheeled ground robot; Intelligent tire; Terrain classification; Fuzzy logic algorithm

Numerical analysis on tractive performance of off-road wheel steering on sand using discrete element method

Yonghao Du, Jingwei Gao, Lehua Jiang, Yuanchao Zhang
Journal of Terramechanics, Volume 71, June 2017,
Pages 25-43, ISSN 0022-4898,

This paper presents a numerical analysis on steering performance including tractive parameters and lug effects. To explore the difference between the turning and straight conditions of steering, a numerical sand model for steering is designed and appropriately established by the discrete element method on the basis of triaxial tests. From the point of mean values and variation, steering traction tests are conducted to analyze the tractive parameters including sinkage, torque and drawbar pull and the lug effects resulting from type, intersection and central angle. Analysis indicates that steering motion has less influence on the sinkage and torque. When the slip ratio exceeds 20%, the steering drawbar pull becomes increasingly smaller than in the straight condition, and the increase of steering radius contributes to a decline in mean values and a rise in variation. The lug effect of central angle is less influenced by the steering motion, but the lug intersection is able to significantly increase the steering drawbar pull along with the variation reduced. However, the lug inclination reduces the steering drawbar pull along with the variation raised in different degrees.
Keywords: Steering; Off-road wheel; Tractive parameter; Lug effects; Discrete element method