The effects of tangential contact stiffness on a harmonically forced friction oscillator

This paper addresses the effects of a compliant contact on the dynamical friction behaviors in mechanical systems. Contact compliance is due to the elastic deformation at the contact point or the surrounding structure. This paper is divided into two parts. The first part focuses on oscillations with continuous macroscopic sliding. An idealized model consisting of a mass sliding harmonically on a massless compliant contact produces the hysteresis feature seen in friction-velocity plots. Transition features, depending on the contact stiffness, friction level, and frequency/amplitude of oscillation, are predicted and quantified. Experiments have been conducted to verify the model. The model and associated analysis provide a means for interpreting experimental transition behaviors. The second part of the paper addresses the sticking dynamics associated with a macroscopic stick-slip process. During a stick, the mass undergoes a microscopic oscillation at the contact. This can involve a microscale stick-slip process. We refer to the entire process as a double stick-slip event. Numerical and experimental studies are compared.