Experimental observation of cross correlation between tangential friction vibration and normal friction vibration in a running-in process

Running-in wear experiments were conducted on a spherical-on-disk tester. Cross correlation between tangential friction vibration and normal friction vibration were studied by time-frequency features and cross correlation coefficient. Variations of tangential friction vibration and normal friction vibration were analyzed by chaos attractors. Experimental results show that the cross correlation is poor in the beginning stage, while two signals are significant correlation when running-in continues and high correlation when reaching the running-in. Variation of cross correlation coefficient which could be used to describe the change of wear states in the running-in process is opposite to the change of friction coefficient. Chaotic attractors of two signals converge as running-in go on and can be used to describe variations in the running-in process.