Roughness-induced transient loading at a sliding contact during start-up

The effects of normal contact vibrations, horizontal rider dynamics, and surface texture inputs are combined to examine dynamic loads at a contact during acceleration from rest to a steady state velocity. A constant sliding friction coefficient is assumed. The surface input is either a sine wave or a quasi-random function. The nondimensionalized system equations are solved numerically for a variety of system and input parameter combinations. The most interesting responses occur when the acceleration duration includes a number of periods of at least one of the system resonant frequencies. It would appear that surface-roughness and waviness can cause the normal motions and force fluctuations that occur during the transitions from static to sliding friction.