PRECISE MEASUREMENT AND ANALYSIS OF BASIC ELEMENTS OF TRAVELING PERFORMANCE OF WHEELS

为了研究越野车辆的行驶性能，过去已经开发了各种类型的测量软地面上的行驶性能的机械量的设备。然而，它们还没有达到令人满意的精度，同时难以向车轮提供驱动扭矩，保持车轮和土壤之间的恒定接触载荷。本文介绍了一种新的测量装置，它能高精度地测量车轮在恒定接触载荷作用下的基本力学量，即扭矩、接触载荷、牵引力、车轮表面的正应力和切向应力以及土壤的变形。这些量中的大多数在在线计算机显示器上可视化。在此基础上，编制了基于弹塑性次加载面模型的有限元程序，分析了刚性车轮转动引起的土体变形。该程序的主要特点是能恰当地分析土壤的弹塑性变形，能真实地描述车轮与土壤接触面的边界条件，并结合库仑摩擦定律，能自动保持接触载荷恒定。此外，它还包括两个阶段，即车轮垂直下降的下沉阶段和车轮滚动行进的滚动阶段。计算结果与试验数据的比较表明，该程序的分析可以定性地描述试验数据的总体趋势，但要定量预测车轮的行驶性能，还需作一定的修正。

In order to study the traveling performance of off-road vechicles, various types of apparatus measuring mechanical quantities of a traveling performance on a soft ground have been developed in the past. They have not achieved, however, a satisfactory accuracy as yet, while it is difficult to provide a driving torque to a wheel, maintaining a constant contact load between a wheel and soils. In this study, a new apparatus was developed, which is capable of measuring the basic mechanical quantities, i.e. torque, contact load, drawbar-pull, normal and tangential stresses on the wheel surface and the deformation of soil under a constant contact load with high accuracy. Most of these quantities are visualized on an on-line computer display. Further, a finite element program based on the subloading surface model of elasto-plasticity has been developed to analyze the soil deformation by the rotation of a rigid wheel. The main features of this program are to analyze suitably the elastoplastic deformation of soil, to describe realistically the boundary condition at the contact surface between the wheel and the soil, incorporating the Coulomb's friction law, and to keep the contact load constant automatically. Besides, it consists of two stages, i.e. the sinkage stage in which a wheel goes down vertically and the rolling stage in which a whee travels rolling. The comparison of the calculated results with the test data verified that the analysis by this program can describe qualitatively the general tendency of the test data but is required a modification for the quantitative prediction of traveling performance of wheel.