... in Fig. 7 Fig. 7 Normalized tangential contact stiffness K ′ variation with normalized normal load W ′ given different fractal dimensions D Figure 7 depicts the nonlinear relationship between tangential contact stiffness and normal load when the fractal dimension was in the interval...

..., meanwhile, decreases the critical contact area, so those microcontacts yield elastic deformation, which, in turn, increases the normal and tangential contact stiffnesses; the contact stiffness increases with increasing contact load due to the increase in the real contact area. The contact stiffness follows...