Chaotic Property And Correlation Of Friction Force And Friction Vibration In Wear Process

In order to enrich the basic theory methods of tribological study and develop the quantitative study of tribological complex problems, in this paper, we did research on the friction force signal and friction vibration signal quantitatively based on the theory of chaos, researches were carried on the evolution of chaos property and the correlation of friction force and friction vibration. The works are mainly shown in the following:Firstly, the experiments were taken on a pin-disk tribology test equipment under same working and lubrication condition but with four different common friction pair material as aluminum-quenched 45 steel, copper-quenched 45 steel, GCr15- quenched 45 steel,20 steelquenched 45 steel, the friction force and friction vibration signal was gathered in the acquired with computer.Secondly, the effect of noise on the Lorenz signal was quantitative studied, it reveals that noise has huge impact in the frequency-domain, embedding dimension, time delay, maximum Lyapunov exponent, correlation dimension of the chaotic signal. EMD method works well on denoising the noise polluted Lorenz chaotic signal, and the researches was carried on the denoising of chaotic signal by empirical mode decomposition method(EMD) to prove this method is fitted in denoising chaotic signal. Then the friction force and friction vibratin signal was denoised by EMD method, the results showed that EMD is applicable in denoising the real friction signal, and the comparatively pure friction signal which could be analysed was extracted.Thirdly, in order to reveal the evolution of chaotic property in the wear process qualitatively, the friction signal gathered from the experiments was reconstructed to form the chaotic attractor and recurrence plot respectively by the delay-coordinate method. The results showed that: all the friction signal gathered from the experiments completely accords with the law of “the trajectory is a spiral and retractile track firstly- making a circle movement sticking to a point- finally making a spiral and spread movement quickly. The evolvement rule of change trajectory of dynamics processes is from unstable to stable, and then to unstable”.Then, several kinds of chaotic characterizations of correlation dimension, recurrence rate, determinism, divergence, entropy, laminarity were used to calculate the change rule of chaotic property of wear process. The result shows that: the fractal dimension and convergence of wear attractors in the wear process; the amout of information contained in the friction system; the stability of friction system accord with the change rule of “upside down bath curve”, which could reflect the time and stage of wear process, tough the shape or the size are different.At last, cross recurrence plot and cross recurrence rate,cross determinism, cross average line length, these three kinds of characterizations were used to measure the correlation of friction force signal and friction vibration signal qualitatively and quantitatively. The result shows that the friction force and friction vibration is strongly correlated in the phase space.