Normal Revised Model of Joint Interface Distinguishing Elastic and Plastic Deformation

Abstract

On the basis of Hertz elastic theory and fractal geometry theory, one normal contact modification fractal model of fretting joint interface, following the character of the harsh surface bulge's deflection, smoothness and continuity of normal contact load exerting surface asperity as well as differentiating severely elastic deformation and plastic deflection, is proposed. The power function equation between surface summit's normal elastic contact load and its normal deformation is presented. Furthermore, the solving rule of differential function not partial differential function to attain fretting joint interface two bulges' interacting normal contact stiffness is addressed. The digital simulation curves reveal that real contact area firstly increases and afterwards decreases with the augment of fractal dimension at the given normal contact load. Real contact area may outright add by increasing normal contact load or reducing surface roughness. Fretting joint interface normal contact stiffness enhances as the increase of real contact area, normal contact load, relating factor or material property parameter, yet an increase in fractal roughness causes a decrease in fretting joint interface normal contact stiffness. Fretting joint interface normal contact stiffness increases when fractal dimension increases from 1 in the smaller range of fractal dimension; nevertheless, fretting joint interface normal contact stiffness sometimes shrinks when fractal dimension increases close to 2 in the larger range of fractal dimension. Conceiving normal contact amendment fractal model of fretting joint interface investigates deeply the practicable contact states between fretting two coarse surfaces.