ABSTRACT
In many approaches to the problem of off-road mobility, contact pressure is a main input parameter. A concrete surface acts something like a bridge that transfers and distributes wheel loads over a greater surface, while a soft surface deforms intensively because the loads are concentrated on a very small contact surface. Numerous papers have proven the importance and practical meaning of the stress state under wheels for measuring and predicting off-road traction (Dąbrowski et al. 2006, Foda 1991, Muro 1993, Hetherington and White 2002, Hetherington and Littleton 1987, Pytka 2007, Shibusawa and Sasao 1996, Shmulevich and Osetinsky 2003, Upadhyaya et al. 1997, Wanjii et al. 1997). In most models, tractive forcesdriving force, rolling resistance, and vertical load-are determined based on an analysis of stress state or stress distribution on a contact surface. These forces are expressed in Bekker’s equations:
∫= τ α αF d( )DR (4.1) ∫= σ α αF d( )RR (4.2) where τ(α) is the shear stress component, σ(α) is normal stress, and α is a measure of a surface of volume over which the stresses accumulate.
