"Stick-slip effect"

The stick-slip effect refers to the jerky sliding of solid bodies moving against each other. This phenomenon occurs when a body is moved whose static friction is significantly greater than the sliding friction.

Imagine a heavy carton that you want to push across a smooth floor. The box is heavy, which is why we have to exert a lot of force to overcome the static friction - i.e. the resistance of the box to move. The carton slides. Due to the smooth surface and the resulting low sliding friction, the carton quickly speeds up. However, the rapid sliding movement of the carton means that we can transfer less force. Eventually, the force acting on the carton is no longer sufficient to overcome its static friction. The carton comes to a standstill, which means we have to apply a lot of force again to overcome it and the process repeats itself. Sticking - releasing - sliding - braking - sticking - releasing ... in reality, this effect happens much faster and manifests itself in a stutter.

Diagrams

This phenomenon occurs in a wide variety of areas. Windscreen wipers stutter across the windscreen of a car. Chalk squeaks when writing on the sheet if you hold it at the wrong angle. Door hinges squeak. And stringed instruments such as the violin or cello would not work because their sounds are produced by vibrations and oscillations between the strings and the strings of the sag.

With tribologically optimised materials, however, this effect is undesirable. The vibrations caused are transferred to the overall construction and cause noises that are often perceived as annoying squeaking or creaking. The desired sliding movement becomes an irregular stuttering and increases wear on the bearing. These effects can be counteracted by minimising the difference between sliding and static friction, using vibration-dampening materials, improving the rigidity of the overall structure (see pre-loaded bearing) or separating the friction partners involved (e.g. by lubrication)