Chaotic characteristics of measured temperatures during sliding friction

In the present work, we aim to investigate the chaotic characteristics of measured temperature signals in the friction process, and further reveal the dynamic behavior of the friction system. Experiments are conducted on a reciprocating tribometer under different working conditions, and the contact temperature is measured by a thermocouple throughout the friction process. The phase trajectories and chaotic parameters are obtained based on the phase-space reconstruction of the temperature time series. The results show that the temperature signals acquired from different tests possess the same dynamic evolution law. As the time goes on, the phase trajectories follow the dynamic rule of “convergence-stability-divergence”. This evolution process corresponds to the stages of the “forming, keeping and disappearing” of the chaotic attractor. In the attractor forming stage, the correlation dimension increases gradually and the Lyapunov exponent varies from negative to positive. Then, both the correlation dimension and the Lyapunov exponent remain at a steady level in the attractor keeping stage. Finally, the correlation dimension decreases and the Lyapunov exponent varies to a negative value in the chaotic attractor disappearing stage. It makes it possible to identify friction states by analyzing the temperature time series.