Prapote Boonsinsuk

Analysis and prediction of tyre-soil interaction and performance using finite elements

Abstract The finite element method [FEM] of analysis previously developed for prediction of rigid wheel-soil interaction is improved and extended to take into account (a) the effect of flexibility of tyre carcass where energy losses now occur in development of mobility, (b) a simpler requirement for specification of boundary condition using input loading, and (c) normal and tangential load stress from the tyre distributed across the tyre-soil interface and varying with slip. The comparisons of analytically computed (predicted) drawbar pull with actual experimentally obtained drawbar pull results for tests in three types of tyres show good correlations. The effect of inflation pressure on development of tyre deformation energy losses can be seen from the analytically computed values.

Tyre flexibility and mobility on soft soils.

Abstract Five model tyres were tested in the soil bin to investigate the effects of wheel flexibility on the tyre-soil performances. Two different soil types were used together with various inflation pressures which governed the tyre flexibility. The results confirm that tyre flexibility contributes significantly to the development of all the energy components [equation (1)] in the tyre-soil system. As can be seen from the contrasting performances shown, increasing the inflation pressure may allow for a favourable increase in the drawbar pull in one soil (frictional soil) so long as the input energy available can be increased, whilst the reverse may be true in the case of the other (clay) soil. The finite element model used satisfactorily confirms the measered values obtained and is seen to be able to account for tyre flexibility as shown in Figs. 11–14.

Tyre load capacity and energy loss with respect to varying soil support stiffness.

Abstract An analytical model is developed to predict the tyre deformation and the resultant energy loss due to tyre flexibility relative to various soil stiffnesses ranging from rigid unyielding support to soft soil. The analysis allows for examination of a pneumatic tyre with respect to the wheel load to be carried, the supporting ground rigidity and the rigidity of the tyre casing. The important tyre characteristics in providing for wheel load capability under motion are demonstrated to be the tyre carcass construction, dimension, inflation pressure and the ability of the tyre casing to recover some of the resultant energy losses incurred by the tyre under motion.

Preconditioning of deep snowpack for off-road vehicle mobility

Abstract This paper addresses several preconditioning techniques for strengthening a deep snowpack in order to support vehicular loadings. The criteria imposed on preconditioning a deep snowpack were: (1) only light commercially-available vehicles or equipment could be used, (2) preconditioning would only be applied to the snow surface and (3) any additives to be used should be easily acquired in remote areas. Viable preconditioning techniques were first evaluated in the laboratory using artificial snow. The techniques explored were surface loading (surcharging), heating and mixing with additives (sand and straw) followed by surcharging. The properties of the laboratory-preconditioned snow were evaluated primarily in terms of footing penetration resistance and Rammsonde hardness. Based on the laboratory results, preconditioning of a deep natural snowpack was carried out. Surcharging the snowpack was achieved by a BV206 Carrier. The preconditioning techniques studied were surcharging, heating and mixing with additives (salt and straw). Various ageing periods were imposed. The load-carrying capacity of the preconditioned snowpack was evaluated by multipasses of two wheeled vehicles (Iltis and 5/4 ton truck). The results indicated that a soft deep snowpack can be preconditioned to the extent that it can support multipasses of wheeled vehicles.

Flexibilität und mobilität von reifen auf weichen böden

Zusammenfassung An funf Modellreifen wurden in der Bodenrinne die Wirkungen der Radflexibilitat im Hinblick auf das REifen-Bodenverhalten untersucht. Zwei verschiedene Bodenarten zusammen mit unterschiedlichen Luftdrucken bestimmten die Flexibilitat der Reifen. Die Ergebnisse bestatigen, das die Flexibilitat der Reifen signifikant zur Bildung aller Energiekomponenten (Gl.1) im System Reifen-Boden Beitragt. Wie man vom gegensatzlichen Verhalten erkennt, so kann steigender Luftdruck zu einem gunstigen Anstieg der Zugkraft in dem einen Boden (Reibungsboden) fuhren, solange die verfugbare Eingangsenergie erhoht werden kann, wahrend der umgekehrte Fall bei einem anderen Boden (Tonboden) richtig sein mag. Das Finite-Element Modell bestatigt befriedigend die gemmessenen Werte und kann die Flexibilitat der Reifen, wie in Bildern 11 bis 14 gezeigt erklaren.