Publication news

Journal of Terramechanics, Vol. 48, Issue 2

Sara Johnson, Guangxing Wang, Heidi Howard, Alan B. Anderson
Identification of superfluous roads in terms of sustainable military land carrying capacity and environment
Journal of Terramechanics, Volume 48, Issue 2, April 2011, Pages 97-104, ISSN 0022-4898, 10.1016/j.jterra.2010.10.001.
Abstract: A great challenge the US military land managers are often faced with is how to optimize road networks in order to maintain roads (including all roads, trails, and paths) for the purpose of military training and reducing negative impacts on environment. In this study, a methodology was developed to identify superfluous roads for being closed in terms of both sustainable military land carrying capacity and environment for Fort Riley. In this method, Geographic Information Systems (GIS), remote sensing, and landscape analysis technologies were combined to derive various spatial data layers of factors that had significant impacts on both military training and environment. The factors included maintenance cost of roads, road access area, military training intensity, soil erosion, water quality, landscape fragmentation, and noise production. The factors were quantified and normalized. A spatial multicriteria decision was then developed to obtain the weights of the factors, combine the data layers, and derive a priority map of all the roads for being closed. This map summarized the negative and positive impacts of the factors on environment and military land carrying capacity and can provide the US military land managers with useful guidelines and tools for determining superfluous roads in terms of both sustainable military training and environment. It is expected this effort can provide a method to quickly ascertain which roads are most cost-effective for being closed without hindering the mission and at the same time with benefits for environmental protection and thus provide the land managers with a comprehensive analysis and assessment of alternatives at their disposal.
Keywords: GIS; Superfluous roads; Landscape analysis; Military land management; Remote Sensing; Spatial multicriteria decision

Phillip J. Durst, George L. Mason, Burney McKinley, Alex Baylot
Predicting RMS surface roughness using fractal dimension and PSD parameters
Journal of Terramechanics, Volume 48, Issue 2, April 2011, Pages 105-111, ISSN 0022-4898, 10.1016/j.jterra.2010.05.004.
Abstract: Off-road vehicle performance is, in part, related to the ride comfort of the vehicle while operating on rough terrain. The surface undulations altering vehicle ride over homogeneous areas are defined, by the US Army, as a single number descriptor entitled root-mean-square (RMS). A current need exists to attribute large geographic areas with RMS values in order to better support vehicle speed predictions with remotely sensed data. The RMS is typically computed using centimeter scale data, which can be difficult and time consuming to collect. A technique to extrapolate RMS for large areas was developed based on meter-scale data to predict RMS using a combination of fractal dimension and spectral analysis. Validation of the extrapolation technique was based on 43 vehicle ride courses with 30-cm data. For each ride course, a two dimensional fractal dimension (FD) was computed using the divider method, and a discrete Fourier transform (DFT) was used to compute the power spectral density (PSD). A regression analysis was performed to search for correlations between RMS, FD, and PSD given fixed-slope power law fit parameters. Using a stepwise model selection, a statistical model for rapid predictions of RMS was developed. The RMS was computed from FD and the PSD DC offset to within 80% agreement using a linear model.
Keywords: Surface roughness (RMS); Fractal dimension (FD); Power spectral density (PSD); Off-road performance; Ride quality; Prediction; Modeling

Kaiming Xia
Finite element modeling of tire/terrain interaction: Application to predicting soil compaction and tire mobility
Journal of Terramechanics, Volume 48, Issue 2, April 2011, Pages 113-123, ISSN 0022-4898, 10.1016/j.jterra.2010.05.001.
Abstract: Tire/terrain interaction has been an important research topic in terramechanics. For off-road vehicle design, good tire mobility and little compaction on terrain are always strongly desired. These two issues were always investigated based on empirical approaches or testing methods. Finite element modeling of tire/terrain interaction seems a good approach, but the capability of the finite element has not well demonstrated. In this paper, the fundamental formulations on modeling soil compaction and tire mobility issues are further introduced. The Drucker–Prager/Cap model implemented in ABAQUS is used to model the soil compaction. A user subroutine for finite strain hyperelasticity model is developed to model nearly incompressible rubber material for tire. In order to predict transient spatial density, large deformation finite element formulation is used to capture the configuration change, which combines with soil elastoplastic model to calculate the transient spatial density due to tire compaction on terrain. Representative simulations are provided to demonstrate how the tire/terrain interaction model can be used to predict soil compaction and tire mobility in the field of terramechanics.
Keywords: Tire/terrain interaction; Finite deformation; Finite element; Soil compaction; Tire mobility 

U. Solomon, Chandramouli Padmanabhan
Hydro-gas suspension system for a tracked vehicle: Modeling and analysis
Journal of Terramechanics, Volume 48, Issue 2, April 2011, Pages 125-137, ISSN 0022-4898, 10.1016/j.jterra.2010.12.001.
Abstract: Tracked vehicles fitted with torsion bar suspensions are limited in their ability to achieve high mobility. This limitation is due to the linear characteristics and the consequent poorer ride performance. Hydro-gas suspensions due to their inherent non-linear behavior can provide higher mobility and better ride comfort performance. The hydro-gas suspension model has usually been developed from experimental force–displacement characteristics, which requires availability of suspension hardware. 

In this paper, a hydro-gas suspension system is modeled using polytropic gas compression model to represent the spring characteristics, while the damper orifices are modeled using hydraulic conductance. The analytical model is then validated with experiments individually for spring and damper flow characteristics and then as a suspension-wheel assembly in a test rig. The validated suspension model is incorporated in an in-plane model. Using this model, simulation is carried out for sinusoidal inputs of different wavelengths, amplitudes and vehicle speeds. The simulation model is validated with data measured on a vehicle traversing an APG course. The proposed model agrees very well with the measured data. Based on the validated model, studies on the influence of suspension parameters on the ride comfort of a tracked vehicle are carried out.
Keywords: Suspension; Hydro-gas suspension; Damper; Tracked vehicle

S. Loutridis, Th. Gialamas, I. Gravalos, D. Moshou, D. Kateris, P. Xyradakis, Z. Tsiropoulos
A study on the effect of electronic engine speed regulator on agricultural tractor ride vibration behavior
Journal of Terramechanics, Volume 48, Issue 2, April 2011, Pages 139-147, ISSN 0022-4898, 10.1016/j.jterra.2010.10.002.
Abstract: In this study, the effect of electronic speed adjustment on tractor ride vibration levels is examined. With normal pedal operation the engine rotational speed drops with an increasing load. The electronic regulator provides a constant speed mode of operation independent of the load. Vibration levels were measured under different operating conditions and surfaces. As a first series of tests, the tractor was driven on a conglomerate bituminous track at speeds of 20, 25 and 28 km/h. Vibration was measured upon the surface of the operator seat simultaneously in the x, y and z directions. The reference axis system was that defined by the ISO 2631-1 [1]. The weighted r.m.s. acceleration was found to be between 8% and 8.6% higher for the case where operation with electronic speed adjustment had been selected. Secondly, cultivating was chosen as the field task and the vibration was measured while the tractor was traversing a rough farm track at speeds of 6, 7.5 and 9 km/h. In this case, the vibration levels with automatic speed adjustment were between 4.3% and 8.6% lower than when driving with normal foot pedal operation. From the above results, we may infer that electronic speed regulation should not be used in transportation on asphalt country roads. On the contrary, it seems that electronic regulation has an advantage when used in typical field tasks such as cultivating.
Keywords: Agricultural tractor; Whole-body vibration; Ride comfort; Electronic engine speed regulator

Gareth Meirion-Griffith, Matthew Spenko
A modified pressure–sinkage model for small, rigid wheels on deformable terrains
Journal of Terramechanics, Volume 48, Issue 2, April 2011, Pages 149-155, ISSN 0022-4898, 10.1016/j.jterra.2011.01.001.
Abstract: Bekker’s semi-empirically derived equations allow the designers of off-road vehicles to understand and predict vehicle mobility performance over deformable terrains. However, there are several underlying assumptions that prevent Bekker theory from being successfully applied to small vehicles. Specifically, Bekker’s sinkage and compaction resistance equations are inaccurate for vehicles with wheel diameters less than approximately 50 cm and normal loading less than approximately 45 N. This paper presents a modified pressure–sinkage model that is shown to reduce sinkage and compaction resistance model errors significantly. The modification is validated with results from 160 experiments using five wheel diameters and three soil types.
Keywords: Small wheels; Sinkage; Compaction resistance; Bekker theory

Daryoush Safarzadeh, Shamsuddin Sulaiman, Faieza Abdul Aziz, Desa Bin Ahmad, Gholam Hossein Majzoobi
The design process of a self-propelled floor crane
Journal of Terramechanics, Volume 48, Issue 2, April 2011, Pages 157-168, ISSN 0022-4898, 10.1016/j.jterra.2010.12.002.
Abstract: In order to prevent the hazards associated with the crane application in workshops and factories, a self-propelled hydraulic floor crane with wire remote control was designed. The main focus was directed on remote control of the crane operations such as rotation of booms, rear and forward movements, changing travel speed, steering, braking and hook rotation. This configuration prevents the hazards and damages which may be created due to the proximity of operator to crane and provides the feasibility of utilizing the crane in crowded manufacturing areas, fields and hazardous environments. Research into the stability of crane on a slope route was also performed to obtain the equations of stability in static and dynamic conditions and recognition of the ways to enhance the stability. To validate the research work, a scale-model prototype was built to test the manner of controlling the crane operations from afar.
Keywords: Crane; Hazards; Hydraulic; Remote control; Self-propelled

P. Raybaud
Corrigendum to “International Society for Terrain-Vehicle Systems, The Soehne–Hata–Jurecka Award and the Bekker–Reece–Radforth Award” [J. Terramech. 48 (2010) 1–2]
Journal of Terramechanics, Volume 48, Issue 2, April 2011, Page 169, ISSN 0022-4898, 10.1016/j.jterra.2011.02.001.