N. Dibagar; A. Mardani; A. Modarres Motlagh; H. Jafari
Abstract
Introduction: Encountering soil from the viewpoint of management and product manufacturing has always been considered important, and an attempt is always made hat the tools and contrasting methods of soil be designed in such a way that itself prevents, as much as possible, the destructive consequences ...
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Introduction: Encountering soil from the viewpoint of management and product manufacturing has always been considered important, and an attempt is always made hat the tools and contrasting methods of soil be designed in such a way that itself prevents, as much as possible, the destructive consequences or energy waste that include economical or environmental limitations. Enhancing the soil encountering methods, quality reformation, and its related equipment, requires performing reliable tests in actual soil conditions. Considering the complexity and variety of variables in soil and machine contrast, this is a hard task. Hence, the numeral simulations are the key of all optimizations that illustrate efficient models by removing the costly farm tests and reducing research time. Tire is one of the main factors engaged with soil, and it is one of those tools that are discussable in both farms, and software environments. Despite the complexities in soil behavior, and tire geometry, modeling, tire movement on the soil has been the researchers’ objective from the past.
Materials and methods: A non-linear finite element (FE) model of the interaction of a non-driving tire with soil surface was developed to investigate the influence of the forward speed, tire inflation pressure and vertical load on rolling resistance using ABAQUS/Explicit code. In this research numerical and experimental tests were done under different conditions in order to estimate tire rolling resistance. In numerical tests, the soil part was simulated as a one-layer viscous-elastic material with a Drucker-Prager model by considering realistic soil properties. These properties included elastic and plastic properties which were obtained in the soil laboratory using relevant tests. The soil samples were prepared from the soil which was inside the soil bin. The same soil was utilized in experimental tests. Finite strain hyper elasticity model is developed to model nearly incompressible rubber materials for the tire. Tire model consisted of three components: tread, rubber and ring. Using a soil bin and one wheel tester with their related equipment, experimental tests were carried out in the workstation of mechanics of bio system engineering department of the Urmia University. This system includes various sections such as soil storage in dimensions of 22×2×1 meter, tools carrier or tracker, soil processing equipment, dynamic system, evaluation tools and controlling systems. In order to launch the collection and supply required power for wheel carrier, an industrial three phase electromotor with 22 kW (30 hp) was used. Both numerical and experimental tests were done at three levels of wheel dynamic load (1, 2, 3, 4 and 5) kN, tire inflation pressure (100, 200 and 300) kPa and four levels of speed (0.25, 0.45, 0.65, 0.9 and 1.15) m s-1 to obtain the rolling resistance of the tire.
Results and discussion: In order to evaluate the performance of final non driving tire-soil model to estimate the rolling resistance, numerical results were compared with preliminary experimental data obtained from the soil-bin tests. The comparison showed reasonably good agreement between the computed and measured general pattern of the rolling resistance at the tire-soil interface under different speeds, vertical loads and inflation pressures. In both tests, a specified relation was not seen between tire velocity and its rolling resistance, as it was not seen in empirical models such as Wismar and Luce. Correlation coefficient between experimental and numerical data, in the minimum and maximum value of tire inflation pressure was computed to be 0.06 and 0.016 percent, respectively. The amount of tire rolling resistance significantly increased with increase of tire vertical load. Correlation coefficient between experimental and numerical data, in the minimum and maximum vertical loads was computed to be 80 and 87 percent, respectively. Gent and Walter obtained the same results. The tire inflation pressure and rolling resistance variables had inverse relation to each other in both numerical and experimental tests. Correlation coefficient between experimental and numerical data was computed to be 97 and 73 percent in the minimum and maximum tire inflation pressure, respectively. The gradient of changes in tire inflation pressure - rolling resistance diagram was less in numerical tests. This was because of differences between real properties and the properties entered into the software.
Conclusions: To conclude, in this investigation a new 3D tire-soil model was simulated which has specific features. The experimental results showed that the numerical data of estimation of non-driven tire rolling resistance were reliable. In both tests, the effect of changes in tire forward speed on rolling resistance was not significant.The amount of the tire rolling resistance significantly increased with increasing tire vertical load. Changes in tire inflation pressure and rolling resistance had an inverse relation with each other in both numerical and experimental tests. The slope of rolling resistance - inflation pressure diagram in numerical tests was less than the same diagram in the experimental tests.
