Journal of Terramechanics最新文献

Modeling the force interaction between a wheel and the ground is necessary when evaluating the effectiveness of a vehicle’s mobility on challenging terrain. Soft soils with low bearing strength are a particularly difficult medium for wheeled vehicles. Helical scrolls have shown promise as an alternative to wheels which can work across a range of terrains, warranting a detailed terramechanics study to model their capabilities. Most of the existing terramechanics literature is limited to wheels and often employs an apparatus to study single wheels in a fixed geometry.

This paper describes the design and implementation of a novel apparatus capable of housing a range of scroll geometries and configurations. The apparatus is comprised of a soil container, carriage to drive the scroll in two operating configurations, and a surrounding frame that enables both vertical and horizontal motions of the carriage. The carriage is outfitted with a drive system and instrumentation to measure the sinkage, stress, and drawbar pull values required for a terramechanics characterization. Initial stress-sinkage curves for three different scroll configurations align with expected results and provide a proof of concept that the proposed apparatus can successfully measure differing geometric parameters and can be used for further terramechanics characterizations.

The study of deformable soils is one of the key factors in determining the tire, vehicle and/or agricultural tool design parameters. This literature review provides a brief overview of soil classification, soil testing, soil constitutive models, and numerical approaches utilized to model soil-tire/tool interaction. In the past, empirical, semi-empirical, and analytical soil models were used in these studies. However, some limitations occurred in terms of characterization of soil-tire/tool interaction in detail due to a large number of variables such as cohesion, moisture content, etc. In the last few decades, the finite element (FE) method was used with different formulations such as Lagrangian, Eulerian, and Arbitrary Lagrangian Eulerian to simulate the soil-tire/tool interaction. Recently, particle-based methods based on continuum mechanics and discrete mechanics started to be employed and showed good capability in terms of modeling of soil deformation and separation. Overall, this literature review provides simulation researchers insights into soil interaction modeling with tires and agricultural tools.

Distinct physical properties of red clay soil in hilly and mountainous regions of southwest China, including high adhesiveness and density, challenge the operation of agricultural machinery. A scarcity of accurate discrete element simulation parameters for this soil type restricts computational modeling. The study was focused on red clay soil with a moisture content of 12.50% ± 1% and a measured repose angle of 35.54°. The soil's inherent physical properties were identified through experimental assessments. Soil contact mechanical parameters were obtained from the GEMM database, and optimal contact parameter ranges were determined using Steepest Ascent Experiments, with the simulated soil particle repose angle serving as the response value. A second-order regression model was developed using a quadratic regression rotation orthogonal combination test. By taking the actual repose angle as the optimization criterion, parameters were optimized. The optimal contact mechanical parameters in EDEM simulations were identified as: JKR surface energy at 8.981 J/m², recovery coefficient at 0.474, dynamic friction coefficient at 0.196, and static friction coefficient at 0.45. The model yielded a repose angle of 36.21°, closely corresponding with the observed value, with a relative error of 1.80%. The parameters calibrated in this study offer a valuable reference for future soil-tool interaction studies and tillage implement optimization in these regions.

The dynamic behavior of the vibratory drum of a soil compactor for earthworks is known to be affected by soil stiffness. Real-time monitoring techniques measuring the acceleration of vibratory drums have been widely used for soil compaction quality control; however, their accuracy can be affected by soil type and conditions. To resolve this problem, a novel deep learning-based technique is developed. The method allows the regression estimation of soil stiffness from vibration drum acceleration responses. By expanding the range of applicability and improving accuracy, the proposed method provides a more reliable and robust approach to evaluate soil compaction quality. To train the estimation model, numerous datasets of noise-free waveform data are numerically generated by solving the equations of motion of the mass–spring–damper system of a vibratory roller. To validate the effectiveness of the proposed technique, a field experiment is conducted. A good correlation between the estimated and measured values is demonstrated by the experimental results. The correlation coefficient is 0.790, indicating the high potential of the proposed method as a new real-time monitoring technique for soil compaction quality.

Ocean Worlds such as Europa and Enceladus are known to harbor subsurface liquid water oceans under their icy crust and are high-priority targets for in situ exploration. Compared to the Moon and Mars, Ocean Worlds likely present a significantly more challenging environment for surface mobility systems due to the extremely cold temperature, high radiation dosage, and poorly constrained material properties under these conditions. Small-diameter wheels such as those used by Mars rovers are prone to slip-sinkage in loose soil and damage from sharp rock and ice formations. A 4-wheel rover with a simple drive system and large deployable compliant tires is proposed as a solution for extreme terrain mobility on Ocean World surfaces. The present work describes the design and construction of a single wheel test rig and a prototype large-diameter deployable wheel for Ocean World rovers and initial test results. The test rig allows independent control of the vertical load, slip ratio, slip angle, and camber angle, and accommodates large-diameter deployable wheels. The test rig features a modular test bed that can simulate varied surface features such as fine-grained ice, smooth hard ice, sharp ice formations, and large ice boulder fields.

This work describes an automatic detection method of obstacles covered by snow. The method is based on the detection of statistical anomalies relative to an estimated background image which contains no obstacles. The sensitivity of the detection can be adjusted by a specified probability of false alarms, and the obstacle detection confidence is characterized by a probability of detection. Statistical properties of the background image are estimated from the given image without additional information on the background. The visible height of obstacles above the snow is related to the actual height of the obstacles above the ground, so that an operator can estimate the actual height of the snow covered obstacle. The developed method requires no training, is self-calibrating to the cluttered images, operates with a single given image, and aligns with a detection quantification adopted in the receiver operating characteristic framework.

The mobility of vehicles in off-road environments is critical for many applications. Predicting the tire-soil interaction is a challenge, especially in non-linear deformable terrain. This paper presents an overview of the bibliographic references on tires–deformable soil interactions after the 2000's, identifying the gaps in the literature. The capabilities and challenges of different modeling frameworks used for mobility (i.e., empirical, semi-empirical, and physics-based) are discussed; special emphasis is given to continuum-based frameworks. A summary of terrain material models used to approximate the behavior of coarse and fine-grained soils is provided with practices used to characterize such materials. A review of tire models for deformable soil navigation and the tire-soil interfaces is provided. Strategies to validate all these models are presented. Finally, the application of these studies for assessing the sensitivity concerning input parameters (e.g., velocity, inflation pressure, and normal load), multi-pass, multi-layered soils, wet soils, and fully integrated multi-body vehicle models are discussed. The final contribution of this review paper is a summary table that synthesizes the extensive bibliographic review. Overall, this work highlights a lack of physics-based trafficability studies in wet and plastic deformable soils. Moreover, studies on contact adhesion, stone picking, multipass, and cornering also need improvement.

Rotary claws are used to break soil into small pieces and plow the soil flat. In this study, rotary claw development in tiller machines was evaluated using both equipment and the discrete element method (DEM). However, evaluation through equipment is imprecise and time consuming. Although DEM is an effective method for modeling the movement of granular materials, it requires numerous parameters to ensure accuracy, which must be determined through experimental evaluation and comparison. To resolve this concern, an image processing method was developed that leverages point cloud data obtained from a depth camera to capture changes in soil shape, distribution, and soil clod size before and after tilling. The effect of soil moisture content and claw rotation speed on soil clod formation and decomposition was evaluated. The experimental results show that the location, number, and soil clod size vary with soil moisture content and claw rotation speed. The results were compared with the DEM simulation to reconcile differences and confirm the feasibility of the proposed method. The model experiment system for soil clods and the image processing method facilitates a quantitative comparison between experimental and DEM simulated soil dispersal, which accelerates the search for DEM parameters to reproduce the tilling.

The Bekker-Wong soil-wheel interaction model has been widely adopted in the terramechanics field. This model requires the soil to be characterised using a Bevameter, which entails performing in situ plate sinkage and shear stress tests. Bevameter soil characterisation is not a standardised test procedure, and the test setup may influence the identified soil model parameters. This study investigates the influence of the following five factors for partially saturated sandy soil: I) soil preparation method on pressure-sinkage, II) soil preparation method on shear stress, III) torsional vs. translational shear mechanism, IV) shear contact area, and V) the influence of shear velocity. The results indicate that the influence of soil preparation on pressure-sinkage response is substantial, exhibiting an order-of-magnitude difference. The influence of soil preparation on shear tests is notable, but less significant. The shear mechanism, shear contact area and shear velocity exhibited a maximum absolute shear stress difference of 18%, 20% and 10%, respectively. Moreover, depending on the test setup configuration and data processing decisions, the estimated internal soil friction angles ranged from 16.5 to 37.5° for the same soil. The findings are expected to have significant implications for the prediction of vehicle drawbar pull using the Bekker-Wong model.

The capacity of soil-burrowing animals to move freely in sticky soil is a motivational trait for developing soil-engaging tools with high operational efficiency. Meanwhile, outstanding hydrophobicity, chemical stability, and corrosion resistance make ultra-high molecular weight polyethylene (UHMW-PE) a potential option for reducing soil adhesion. This study looked into the viability of combining a domed surface inspired by the micro-convex structure of the dung beetle skin with the UHMW-PE as a surface coating to reduce sliding resistance. The sliding resistances of three plates (a flat plate of carbon steel, a flat plate of UHMW-PE, and a domed plate of UHMW-PE) were assessed under varied operating and soil conditions. In each treatment, the tested plate was dragged for 0.7 m of the soil bin length, and the sliding resistance was recorded using the distributed stress and strain test and analysis system (DH3820 N). The results revealed that in all treatments, the sliding resistance of the UHMW-PE domed plate was significantly lower than that of the flat steel plate. Furthermore, the UHMW-PE domed plate outperformed the other tested plates in reducing sliding resistance in more moist and sticky soils, paving the way for the development of highly practical and effective soil-engaging tools.