Modeling planar contact vibrations excited by surface roughness
Patankar, Harshal Prakash
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Dynamic response of the bodies in contact has been of interest since Gray and Johnson (1972) analyzed the case of bodies in rolling contact excited by the surface roughness. Studies have also been conducted dealing with the waviness as a source of excitation such as the work done by Nayak (1975). The present study focuses on the case of dry sliding contact between two surfaces. While dealing with such problems it is often of interest to analyze the effect of nominal area of contact, normal load, sliding speed and surface roughness on the characteristics of vibrations. This study aims at modeling surface profile of the stationary component as a physical filtering of the roughness of the moving surface. This approach builds up on the simulation work done by Soom and Chen (1986). A simple system of block sliding against rigid surface is considered. The system is modeled mathematically with the help of available literature (Hess and Soom, 1992) and is simulated in Simulink. It is found that a first order low pass filter with a cut off frequency dependent on the size of the block provides a useful approximation for the effective roughness input. Sensitivity of angular motion to the coefficient of friction is clearly observed in the simulations. The amplitudes of normal and angular accelerations are found to be highly sensitive to the relative velocity of sliding. After comparing the simulation results with the experimental findings by Hess and Soom it is clear that assuming a perfectly flat block under-predicts the cut off frequency representing the filtering due to the block. This might be due to the presence of large scale waviness in two or three dimensions.