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The understanding of wheel-soil interaction under longitudinal and lateral slip conditions is very important for off-road vehicle dynamics. However, understanding the physics of wheel-soil interaction is not easy, especially with uncertain operational environment and with the limitation of current measuring technique and hardware. This paper explores important aspects of off-road vehicle mobility using as a case study a 7 degree of freedom (DOF) vehicle model under steady-state cornering. In the evaluation of the vehicle response over a two-dimensional (2-D) terrain profile the load transfer due to cornering was taken into account. The tractive and the cornering vehicle capabilities were predicted using an algorithm that chooses the appropriate tire model (rigid or flexible) and finds the optimal geometry of the contact patch.

The most popular semi-empirical models for predicting different aspects of the pneumatic tires performance under steady-state conditions are the Friction Ellipse Model (FEM) and the Magic Formula Model (MFM). The Friction Ellipse Model calculates the longitudinal and the lateral forces in the tire contact patch based on the slip ratio, the slip angle, the normal forces at the tire, and the friction coefficients between the tire and the road surface. The Magic Formula Model describes the cornering forces, the braking forces, and the aligning moment as functions of the slip ratio, the slip angle, and the normal forces at the tire.

The modeling of the terrain/road surface is a very important and challenging task in off/on-road vehicle dynamics simulation, road construction, and stochastic road surface assessment and identification. Various studies have been focused on on-road or on off-road terrain modeling, respectively. Most of these studies developed one-dimensional terrain/road models for specific applications. The approaches used to model paved surfaces differ, usually, from those employed to simulate unprepared terrain, since they must address different uncertainty ranges, linear or non-linear profiles, with normal or non-normal statistical distribution. From the practical point of view, one also needs to be able to reconstruct a representative terrain model from a limited set of measured data.

One fundamental difficulty in understanding the physics of the off-road traction and in predicting vehicle performance is the variability of the terrain profile and soil parameters. These operating conditions are uniquely defined at a given spatial location and a given time. It is not practically feasible, however, to measure them at a sufficiently large number of points to be able to accurately represent the terrain in models. This renders traditional analysis tools insufficient when dealing with rough deformable terrain. We employ stochastic analysis to capture the uncertain nature of this running support and the corresponding vehicle response. From a finite number of observations the terrain profile and soil properties can be modeled as random processes, with the actual operating conditions viewed as a particular realization of these processes. Soil parameters vary substantially from one type of soil to another.

The paper presents the development of delamination resistant composite laminates using interleaving technology. A simple technique which incorporates discrete layers of thin thermoplastic films between wet glass/epoxy prepreg, followed by co-curing, is described. Two types of films having widely different properties were used in order to investigate the effects of film characteristics on composite interlaminar shear strength. Microscopic observations of the specimens after four-point shear testing showed that the failure mode was strongly affected by both the presence and the characteristics of the interleaves.