Empirical Modelling of Frictional Noise and Two-Point Contact Using Ball-On-Disc Tribometer

Wear and its interrelated noise are inevitable occurrences when two materials are in contact with each other. The correlation of the two parameters leads to acoustic study for health monitoring of machines and components. Various empirical models have been proposed using ball-on-disc tribometer using a conventional one ball contact with the disc. In our investigation we used a two-point contact over a rotating disc. To imitate a machine environment where one component is in multiple contact at any instance, a ball holder is designed, which can be affixed on to a conventional tribometer and can engage two balls at the same time sliding over a disc specimen. For the noise parameter, non-contact technique is adapted instead of an acoustic analyzer where a microphone is placed at a fixed distance and in close vicinity to the noise source. The material of the balls was selected to be stainless steel while the material of the disc is mild steel. The balls slide over the disc for a fixed duration at a constant low speed rpm until the wear depth is significant for analysis. In-situ analysis of wear parameters including surface roughness, wear depth and wear profile of the disc was measured systematically. The results from the tribometer are in the form of penetration depth, while the sound signal obtained from microphone is filtered using microphone software and plotted as sound pressure (in dB). The results show a good correlation of wear to the frictional noise at both the contacts and helped us in our subsequent study of modelling wear dependencies. Comparison of wear parameters to noise parameters concludes that the frictional noise is directly related to wear generation at contact.