The Separation and Interfacial Stiffness of Elastoplastic Contact of Self-Affine Fractal Rough Surfaces

Finite element simulations were performed to investigate elastoplastic contact of self-affine fractal rough surfaces. The effects of yield strain, hardening exponent, and Hurst exponent on pressure distribution, separation distribution, mean separation, and interfacial stiffness were examined. The load-separation relation is well described by a piecewise function, including a complementary error function branch at light loads and an exponential branch at intermediate loads. More importantly, after normalization by a reference load scale, both the load-separation and stiffness-load relations collapse onto nearly unified curves, indicating that material hardening and surface morphology mainly rescale the load level rather than changing the basic contact response. Stronger hardening enhances near-contact elastic coupling, increases the probability of small positive separations, and reduces the mean separation. These results provide a unified scaling picture for interpreting separation and stiffness in elastoplastic rough contact.