Colloquia

Summary

Friction—the resistance to relative motion between surfaces in contact— is a fundamental phenomenon in both natural and mechanical systems. The friction resulting from dynamic forces in these systems often leads to wear, degradation, and eventual failure of components. Rapid accelerations and impact loads in engineering systems can cause frictional instabilities such as stick-slip, squeal, and fretting fatigue. Numerous scientific and engineering domains revolve around the understanding and characterization of friction under dynamic conditions. Precision positioning systems used in, for instance, robotics and semiconductor manufacturing are primarily reliant on accurate friction models to design robust controllers that ensure accurate positioning. Additionally, the responsiveness and efficiency of hydraulic actuators, widely used in the aerospace, automotive and machine building industry, are strongly influenced by the frictional behavior along their seals and guiding elements under dynamic conditions. In contrast, in geological systems, sudden slip events in rock gouges reduce frictional strength, potentially triggering seismic activity. Similarly, the understanding of friction under dynamic conditions is also important in more everyday use cases like braking systems, where the friction between the brake pad and brake disc determines the deceleration characteristics and, thus, safety of the system itself. Therefore, an accurate phenomenological characterization of friction under dynamic conditions is essential to anticipate or enhance system performance in both technological and natural systems, because to date, the aforementioned phenomena are not well understood. This has started extensive research on both advanced measurement techniques and more sophisticated friction models able to capture the complexity of frictional interaction under dynamic conditions. Studying friction under extreme dynamic conditions demands carefully controlled experiments and high-end instrumentation capable of capturing rapid frictional behavior. In this assignment, a microtribometer capable of measuring sliding friction under rapid acceleration is designed. Limitations and recommendations are discussed, followed by a conclusion.