Off-road Tire Research Articles

Analysis of Off-Road Tire Cornering Characteristics by Using Advanced Analytical Techniques

ABSTRACT This paper focuses on analysis of the cornering characteristics of an off-road truck tire running under several operating conditions over different soils. The finite element analysis (FEA) method is used to model the Goodyear RHD 315/80R22.5 truck tire, and the smoothed-particle hydrodynamics (SPH) method is used to model the soil. The goal of this research is to provide a virtual testing environment in Pam-Crash software as an alternative to actual tests for FEA and SPH analyses of rolling tire interactions on deformable terrains. The study on the effects of different operating parameters on the cornering performance combined with the sensitivity study can be of interest to tire engineers or vehicle engineers because they provide insight into the design and real-time behavior of a vehicle. Tire and soil models are validated using experimental data and published measurements, showing good agreement. The tire–soil interaction is investigated under different tire conditions, such as longitudinal speed, inflation pressure, vertical load, and slip angle, and under various soil characteristics, such as cohesion, internal friction angle, and rut depth. Cornering force, self-aligning moment, and overturning moment are studied as the fundamental cornering characteristics that affect truck lateral stability and control. Owing to the excessive computational demands posed by the FEA-SPH tire–soil models, we propose unique mathematical relationships for estimating the cornering characteristics of free-rolling as well as driven truck tires in an efficient manner. The genetic algorithm (GA) technique is used to develop relationships between the cornering parameters and operating conditions. We conclude that the identified mathematical relationships could provide very good estimations of the cornering characteristics under a broad range of operating conditions and soils. The GA equations will ultimately be implemented into a full vehicle model to evaluate the full vehicle performance.

Development of a GPU-based multisphere DE–FE coupling method for interaction simulations between an off-road tire and a gravel terrain

For decades, growing interest has been devoted to simulating the tire–soil interaction phenomena using discrete element/finite element (DE–FE) coupling methods. In contrast to the widely used approach that idealizes soils as spherical DEs, a newly developed multisphere DE–FE method has been demonstrated to be more accurate in reproducing such phenomena; however, it requires considerable computational cost for large-scale tire–soil interaction simulations. Therefore, this study aims to develop an efficient graphics processing unit (GPU)-based multisphere DE–FE method based on a CUDA FORTRAN programming environment. To this end, two-level grids are introduced for the parallelization of contact detection for targeted multisphere DEs and subspheres, which helps to find contact pairs for the targeted subspheres of a multisphere DE in an efficient manner. In contrast to existing GPU-based parallelization techniques, which typically use atomic operations to avoid memory access conflicts, this study presents a parallelization strategy to process a contact pair between bounding spheres using one GPU thread to efficiently handle with owner-member relationships between multisphere DEs and their subspheres. In the parallelization for force calculation, our method introduces an efficient technique that utilizes one GPU thread to process a contact pair between subspheres, or between subspheres and FE segments, to reduce the number of repeated calculations. Finally, the developed GPU-based method is applied to analyze the travelling behaviors of a complex-patterned off-road tire on a gravel terrain, and the effectiveness and computational efficiency of this method are validated via indoor soil-bin experimental outcomes as well as serial and parallel simulation results. It is found that a speedup of approximately 38 has been achieved with the aid of the developed method.

Soft Soil, Hard Problem

With the aim of helping engineers with simulating off-road tyre applications, Mechanical Simulation Corporation has added a terramechanics-based tyre model to its CarSim and TruckSim vehicle dynamics simulation software

Comparison of Modeling Methods for Off-Road Tires

Efficient navigation of off-road vehicles heavily relies on the ability to accurately model the interaction between the vehicle and the terrain. One of the most important parts of this interaction is the deformation of the terrain and the tire. Although high-precision methods like finite element method (FEM) simulation can be used for this purpose, they require significant computational power, which is impractical to install in a vehicle for real-time navigation purposes. Therefore, simplified and less-detailed models are essential for on-board installation in real-time applications. In this study, three two-dimensional static terrain–vehicle models are compared to a detailed FEM reference model, and the results are evaluated both from the perspective of accuracy and computational capacity requirements. The analysis sheds light on the effectiveness of each model in the real-time navigation of off-road vehicles.

Soft Soil, Hard Problem

To help engineers with simulating off-road tyre applications, Mechanical Simulation Corporation has added a terramechanics-based tyre model to its CarSim and TruckSim vehicle dynamics simulation software

Haul road condition impact on tire life of mining dump truck

Purpose. Off-road tires (OTR) for mining and earthmoving applications which are specially developed for extreme mine site conditions can take 1020% of transportation costs. Up to 15% of OTR content is natural rubber produced from a rubber tree known as hevea brasiliensis. A significant number of OTR fail before the target life built in by tire manufacturers. This has certain negative impacts on the environment and wildlife due to deforestation effect. Thus, the purpose of the work is to increase the durability or, in the terminology of the operators, the mileage of the OTR. Methodology. The current study represents analyses of new modern digital technology for monitoring the mining haul road condition within a site study on Bogatyr Komir coal mine in North Kazakhstan. The influence of operating conditions was controlled, i.e. road quality, temperature conditions, tire pressure, and other parameters on tire life. Findings. The results show the effectiveness of digital technologies and the possibility of extending the life of tires by following the recommendations of the system in a timely manner. As a result of the analysis of temperature regimes and pressure in tires, especially in summer conditions, recommendations for rational operating conditions were determined, which makes it possible to increase the durability of tires. Originality. Modern operational digital methodology for monitoring open pit mines road condition defines ton kilometer per hour (TKPH) indicator per every trip, which provides on-time information for road design and maintenance. Practical value. Growing worldwide demand is driving the development of the mining industry. In the future, more and more fields with a low content of produced raw materials will be put into operation. The development of deposits with a low content of a useful product means that more rock mass must be moved in order for these developments to be profitable. Transportation costs in low-grade mines can be as high as 70% of mining costs due to more haul trucks and longer roads that need to be commissioned. Thus, an increase in the durability of OTR can give a great economic effect not only in the conditions of the Bogatyr Komir quarry under consideration but also in other mining and processing plants.

Experimental investigation of tire traction performance on granular terrain

In this work, an indoor soil bin traction measurement system is developed to systematically investigate the traction behavior of an off-road tire in interaction with granular terrain. The system is composed of a soil bin, a single wheel test device, a soil mixing/compaction device and its control and data acquisition system. Then the traction performance parameters such as the wheel traction force, sinkage, soil deformation and/or failure mechanism are obtained and investigated by using the system under different working conditions (tire slip, wheel load, tread pattern, granular medium). The experimental results show that the wheel traction force and sinkage present high linear correlation with the tire slip and wheel load. The wheel traction force and sinkage are also found to be directly influenced by the tire tread patterns and granular media. Moreover, with the increase of slip, the shear failure of the soil terrain behind and under the tire becomes more obvious, and the ruts become more blurred. The trend of shear failure mode of the granular terrain from local shear failure to overall failure is becoming ever more obvious. However, under the same tire slip, the wheel loads (7663 N, 10163 N and 12663 N) have little effect on the failure mode of soil terrain. Finally, the experiments indicate that the trafficability of the off-road tires on the gravel terrain is better than that on the sand terrain. The traction performance of the groove tires under the same soil conditions is better than that of the smooth tires.

A multi-sphere DE-FE method for traveling analysis of an off-road pneumatic tire on irregular gravel terrain

In recent decades, extensive effort has been devoted to simulating the tractive performance of an off-road tire on granular terrain using the combined discrete element and finite element (DE-FE) method. Previous works normally idealized irregular gravel materials using spherical DEs, requiring an artificial rolling resistance moment to deal with the interlocking mechanism between irregular granular particles. In this work, we propose a multi-sphere DE-FE method to address this issue. The main appeal is that our presented method can describe the irregular shapes of gravel materials more accurately, and simulates the interactions between non-spherical granular particles and the tire in a natural way. As a result, the artificial rolling resistance moment is not required in our presented method. Three kinds of multi-sphere gravel particle models are established, and the effectiveness of our proposed method is validated via a piling test. Then we calibrate the simulation parameters of tire-terrain interactions using triaxial tests. Finally, the generation method of the multi-sphere gravel terrain is presented, and the tractive performance of an off-road pneumatic tire on irregular gravel terrain is simulated. Our simulation results are found to be in good agreement with experimental data. Numerical results also show that our presented method can better reproduce the traveling behavior of the tire than the widely used spherical DE-FE method in terms of the tractive force and rim sinkage histories.

Prediction of soil vertical stress under off-road tire using smoothed-particle hydrodynamics

Evaluation of vertical stress distribution in clay-loam soil using Smoothed-Particle Hydrodynamics-Finite Element Analysis (SPH-FEA) technique is presented in this research. The moist soil is modelled using the hydrodynamic elastic–plastic material and Murnaghan equation of state, while the tire is modelled using FEA in Visual Environment’s Pam-Crash software. Soil-tire interaction is performed using the node symmetric node to segment with edge treatment method. A single-wheel tester in a soil bin environment was utilized to provide experimental data. The objectives of the experimental test were to (1) calculate maximum subsoil stresses in the subsoil at 1 to 15 passes of a wheel with loads of 1, 2, 4, and 5 kN on soil with moisture levels of 0, 10, 17, and 24%.; (2) calibrate soil with different levels of moisture (3) compare predicted soil stresses with experiments. The maximum stress at 20 cm depth increased with increasing soil moisture and also with high levels of tire load. In contrast, successive traffic showed a decreasing effect on soil stress. The coefficient of determination 0.97 shows the predictions agreed very well with experiments. The moist soil-tire interaction model will be further used to analyze the soil stress in different soil depths and different forward velocity.

Numerical simulation of tire steering on sandy soil based on discrete element method

The steering performance of off-road tires on sandy soil has a great influence on the maneuverability of the vehicle, which has long been studied by scholars. However, the discrete element method (DEM) modeling of tire steering on sand is still lacking. In this paper, an off-road tire steering model on sandy soil is established by using the discrete element method, and the parameters of the sandy soil model are calibrated based on the triaxial compression test and inclined plate experiment. Then, the parameters of the sandy soil model are verified by the reduced-scale single wheel soil bin test under a straight-driving condition. Finally, the influence of the steering radius, roll angle, roll angle, and slip rate on the tire steering process is studied. The results show that a reduction in the steering radius has a slight influence on the drawbar pull and driving torque but a greater influence on the growth of the lateral force, the aligning torque, and the reduction in sinkage. The slip rate and sideslip angle play an important role in drawbar pull, drive torque, lateral force, and torque. The roll angle has a small influence on the drawbar pull and driving torque but a greater influence on the lateral force and the aligning torque.

Longitudinal Vehicle Control based on Off-road Tire Model for Soft Soil Applications

Abstract Autonomous off-road vehicles such as tractors, military vehicles, construction and agricultural machinery require an important power traction to face off mobility issues on soft soils and rough terrains. This paper presents a powertrain controller developed using an adapted Burckhardt tire model based on a Bekker-Wong wheel-soil interaction model according to the plasticity theory and soil mechanics. A Gain Scheduling approach allows the vehicle to maintain the desired reference speed while avoiding the impact of ground conditions. Simulation results show vehicle mobility control through different types of soils.

Rolling resistance prediction of off-road tire using advanced simulation and analytical techniques

This paper focuses on developing a relationship between the rolling resistance coefficient of an off-road truck tire running over different terrains and at various operating conditions. The various operating conditions include tire speed, vertical load, and inflation pressure. The different terrains include dry and moist sand, flooded surface, snow, dense sand, clayey soil, and sandy loam with moisture. The off-road truck tire size 315/80R22.5 is modeled and validated using the finite element analysis technique, while the terrains are modeled and calibrated using smoothed-particle hydrodynamics technique. Artificial neural network and genetic algorithm (GA) are then used to develop a relationship between the rolling resistance coefficient and the terrains and operating conditions. The results of both algorithms are compared to the simulation results in terms of R-square goodness of fit and the mean squared error. Finally, a numerical equation is presented that determines the rolling resistance coefficient as a function of the terrains parameters and the operating conditions. It was found that both techniques provide a suitable solution, however, the GA provides an explicit equation.

Calibration and validation of DEM-FEM model parameters using upscaled particles based on physical experiments and simulations

The real sand is usually idealized by using upscaled particles, due to the large number of particles of tire-sand interaction. This study aims to determine a unique and complete set of DEM-FEM model parameters to improve numerical accuracy of tire-sand interaction after particles idealization. To achieve this aim, a novel method based on experimental design is proposed to calibrate the DEM-FEM model parameters by a series of single-factor numerical calibration tests. Initially, the interaction properties such as equivalent friction coefficients of particle-particle, particle-soil bin and particle-tire are determined successively by comparing experimental test with numerical simulation using the angle of repose as a bulk response. The material parameters of particles are then obtained by modified iteratively to match the stress-strain behavior of the granular assembly in triaxial test. After that, the calibrated parameter set is used to investigate the interaction mechanisms between the off-road tire and the granular terrain. Finally, the simulation results are qualitatively in agreement with the soil bin experiments, which verifies the effectiveness of the calibrated parameter set for the tractive performance analysis of tire-sand interaction.

Numerical analysis on tractive performance of off-road tire on gravel road using a calibrated finite element method–discrete element method model and experimental validation

The interaction between off-road tires and granular terrain has a great influence on the tractive performance of off-road vehicles. However, the finite element method or the discrete element method cannot effectively study the interaction between off-road tires and granular terrain. The three-dimensional combined finite element and discrete element method is applied to handle this problem. In this study, a calibrated finite element method–discrete element method model is established, in which the finite element model of off-road tire is validated by stiffness tests, while the discrete element model of gravel particles is validated by triaxial compression tests. The calibrated finite element method–discrete element method model can describe the structural mechanics of the off-road tire and the macroscopic mechanical properties of the gravel road. Tractive performance simulations of the off-road tire on gravel road under different slip conditions are performed with the commercial software LS-DYNA. The simulation results are basically corresponded with the soil-bin test results in terms of granular terrain deformation and tractive performance parameters versus the slip rates. Finally, the effects of tread pattern, wheel load, and tire inflation pressure on tractive performance of off-road tire on granular terrain are investigated. It indicates that the calibrated finite element method–discrete element method can be an effective tool for studying the tire–granular terrain interaction and predicting the tractive performance of off-road tire on granular terrain.

The interactions between an off-road tire and granular terrain: GPU-based DEM-FEM simulation and experimental validation

Numerical methods have become useful tools for predicting vehicle mobility performance on granular terrain. However, due to the large number of soil particles and complex contact search in tire-granular terrain simulation, time-consuming calculation has become the most critical problem restricting the application of these methods. In this study, an efficient GPU-based DEM-FEM for simulation of the interactions between an off-road tire and granular terrain is implemented to improve computational efficiency. In this method, the main body of calculation is executed on GPU and programmed into an in-house developed code CDFP. The new GPU-based computing framework consists of 14 kernels, including efficient contact calculation between large-scale particles, novel contact calculation between particles and complex tread, contact calculation between particles and boundary wall, internal force calculation of finite elements, and information update. As a result, the efficient contact search and the complex interactions between an off-road tire and granular terrain are accomplished. Based on the self-developed single-wheel test device, an accurate simulation model consistent with the experiment is established. The validity of the proposed method is verified by comparing the simulation results with the experimental results. Finally, the discussion of computational efficiency shows that the proposed GPU-based DEM-FEM can be a powerful tool to simulate the interactions between an off-road tire and granular terrain.

Motion resistance measurements on large lug tyres

Motion resistance of tyres directly contribute to the operational costs of all vehicles. Advances in the design and simulation of large off-road vehicles (construction, mining, agriculture etc.) have increased the need for accurate models of large off-road tyres. Vehicle OEMs use coast down and drawbar pull tests to determine the motion resistance of tyres used. Drum test rigs and motion resistance test trailers can also be used to determine motion resistance. Most research on motion resistance to date have been conducted on passenger car tyres with on-road truck tyres coming into focus. Motion resistance studies on agricultural tyres traversing over deformable terrain have been conducted in the past. However as more off-road vehicle are being used on-road OEMs of off-road vehicle are infesting in motion resistance measurements on non-deformable terrain. This paper compares different methods used to measure the motion resistance of a large lug tyre, as used in agricultural applications, on non-deformable terrain. Some basic considerations that need to be taken into account are the very low longitudinal forces that need to be measured compared to the large vertical load carried by the tyre and tyre operating conditions.

Simulation study on tractive performance of off-road tire based on discrete element method.

In order to improve the applicability and prediction accuracy of the existing simulation test methods of vehicle tractive performance on sandy soil, the off-road tire model using the discrete element method (DEM) under each operating condition is separately established in this paper. The contact parameters of DEM model are calibrated by rubber-sand friction test and soil bin test combined with corresponding simulation test. On this basis, the tire-sand simulation model is calculated under straight and inclining driving conditions, and the variation law of drawbar pull, torque, tractive efficiency and sinkage is obtained. This paper proves the feasibility of DEM simulation in studying vehicle tractive performance, and also provides a systematic parameter calibration method for improving the accuracy of DEM simulation, which is of great significance to enrich vehicle testing methods.

Prediction and validation of terramechanics models for estimation of tyre rolling resistance coefficient

This research focuses on prediction of the rolling resistance coefficient of an agriculture tyre using finite element analysis (FEA) technique, and Bekker and Wismer-Luth models. The tyre-soil interaction is modelled using FEA and smoothed-particle hydrodynamics (SPH) techniques in Visual Environment's PAM-Crash software and validated based on experimental results. A single-wheel tester along with a controlled soil bin at Urmia University, Iran is used to investigate the effect of a tyre's multi-pass and vertical load on the rolling resistance coefficient of an off-road tyre. In order to calculate the rolling resistance of Bekker model, a bevameter device is installed on a carriage moving on clayey-loam soil and a digital penetrometer is used for obtaining the output of Wismer-Luth model. Analysis of experimental data shows that rolling resistance coefficient increases as the vertical load increases and decreases with each pass of tyre. These results are used to compare and evaluate the above-mentioned methods. The results of this study will be used in further research on the interaction between a tyre and soil.

Calibration of DEM-FEM model parameters for traction performance analysis of an off-road tire on gravel terrain

This work aims to determine a complete set of input parameters of the DEM-FEM coupling model, which ensures us obtain more realistic simulation results of the tire-terrain interactions. Firstly, we investigate the macroscopic responses of the gravel sample, the stress-strain curves and deformations, which is finished by the triaxial tests at different confining pressures of 25 kPa, 50 kPa and 100 kPa. Then, the microscopic input parameters of the numerical simulations are obtained by iteratively adjusting the coupling model parameters, which are employed to meet the macroscopic responses of the triaxial tests. Finally, the traction behavior researches of an off-road tire on gravel terrain are carried out by the DEM-FEM coupling model with the calibrated microscopic input parameters mentioned above. The predicted traction performance parameters such as the vertical reaction force, tractive force and tire sinkage are qualitatively in agreements with the corresponding experimental results. The effectiveness of the calibration method using numerical triaxial tests is validated in traction behavior of tire-terrain interactions.

Simulation of Tractive Performance of Off-road Tire on Gravel Road by Combined Finite Element-discrete ElementMethod and Experimental Validation

Simulation of Tractive Performance of Off-road Tire on Gravel Road by Combined Finite Element-discrete ElementMethod and Experimental Validation