EXPERIMENTAL CHARACTERIZATION OF DYNAMIC SOIL TRACK INTERACTION ON DRY SAND

A set of soil-track interaction relations was developed for the mobili ty simulation of tracked or crawler system vehicles on dry, loose sand . These interaction relations were developed specifically for multibod y mobility codes in which the soil-vehicle interaction is represented solely by soil-track interaction forces. By employing plate penetratio n and shear tests, an average pressure-sinkage relation, a shear force -slippage relation, and a sinkage-slippage relation were measured. The se plate test data were sufficient only to describe the soil-track int eraction on hard ground. On soft ground, however, it was found that in termittent sinkages induced by each passage of the road wheels become important. This dynamic contribution is called ''agitation sinkage.'' Based on this observation, the sinkage rate (velocity) was decomposed into elastic and plastic rates; the plastic part consists of normal fo rce-induced, slip-induced, and agitation-induced components. Whereas t he elastic and the first two components of the plastic sinkage rate we re characterized by the conventional plate penetration and plate shear tests, the last term, agitation sinkage, required a new dynamic test in which the sinkage of the track after successive passages of moving road wheels was measured. It is recommended that this new field measur ement technique be adopted to characterize the agitation sinkage for v arious terrains.