Manifestation of non-stationary friction forces in diagnosis of mechanisms

Friction is one of the primary resistive forces in mechanical equipment. Its value determines the friction coefficient, which should remain constant under constant conditions. At the same time, in diagnostic practice, the ability to analyze the time signatures of vibration signals (vibration acceleration) makes it possible to determine the components of friction during machine operation. Several observations of ingot formation processes in a crystallizer, gear engagement, thermal friction milling, and other processes, presented in this article, indicate instability in friction coefficient values. The presented materials do not purport to provide a comprehensive overview or to identify the causes of friction force variations; these can vary widely in each specific case. However, this factor must be considered when analyzing the technical condition, identifying the causes of failure, and making a diagnosis. This article presents the results of studies related to the unstable manifestation of friction forces during the operation of mating machine components.