Impact of Frame Stiffness on Tribological Behaviour of Sliding Interfaces

Sammanfattning: Friction and wear have been concerns to industrialists, scientists and environmentalist for several decades. Many robust models have been developed to address friction and wear and their dependency on various parameters. Numerous experiments have been conducted in the past to model friction and wear. In order to get the experimental results as close as to the real world, the construction of the scientific instrument has to be precise as well. There are several factors that influence the experimental results such as setup of the experiment, dynamics of the instruments etc. These need to be analysed, characterised and suppressed their influence on the experiments. The dynamics of the tribometer when two surfaces are in sliding contact consist of friction induced vibrations and vibrations that influence friction. It is highly complex to device a model which defines interplay of friction and vibrations together. To understand the effect of dynamics of tribometer on sliding contact, vibrations signals were examined. The data was collected by mounting vibrations sensors on the tribometer and the stiffness of the tribometer was modified by changing the spring fixed in the tribometer. The vibrations signals and coefficient of friction data were analysed. The result showed that changing the stiffness of the tribometer did not influence vibrations and coefficient of friction to observable extent, in fact, the vibrations signals were the interaction between the sliding surfaces. The coefficients of friction and vibrations signals for several experiments were similar. The interplay between the vibrations and friction was observed and the vibrations were more like induced vibrations rather than vibrations in the tribometer affecting the sliding contact. The results of experiments comply with by the previously established theories. As the sliding speed decreases, vibrations also decrease and coefficient of friction increases because of increment in the area of contact. This also shows that as vibrations reduces, coefficient of friction increases. The roughness of the pins after the experiments with 40 N/mm spring constant were higher than the ones with 20 N/mm and 120 N/mm, even though the experiment with 20 N/mm were run for a fewer hour. The roughness of the disc for experiment with 120 N/mm were higher than that of the 40 N/mm and 20 N/mm. The experiment with 20 N/mm is higher than 40 N/mm because experiment ran for fewer number of hours than 40 N/mm and 120 N/mm. The roughness results did not have observable patterns and therefore it was concluded that changing one of the components of the tribometer do not influence the experiment at microscale.