FRACTAL TRANSITION MODEL IN PREDICTING STATIC FRICTION COEFFICIENT

There is a fractal characteristic in most engineering surfaces. Effects of the surface fractal parameters D, G and the material parameter. on the static friction coefficient are discussed. The predicted static friction coefficient increases with the increase of normal load. This coincides with the fact that static friction coefficient is very low under very small normal load condition. Second, a fractal transition model is proposed which takes into account the change of fractal dimension D. The load-contact area relationship based on fractal transition model is not simply an exponential function, and the prediction correlates well with the experimental results. The predicted static friction coefficient based on fractal transition model first increases with the increase of load, and then decrease with the increase of load. The transition point is near D=1.5.