Triboelectric behavior of pin-on-disc interfaces in the running-in process

Accurately characterizing the running-in process of metallic friction pairs is crucial for improving running-in quality, shortening running-in time, and reducing running-in costs. Friction-induced electrical signals reflect the generation and evolution of charges at the friction interface during sliding, and their variation patterns can characterize the running-in and wear behavior of friction pairs. This study conducted running-in and wear tests on a metal friction pair using the 40Cr and AlSn40 pair material on a reciprocating friction and wear tester. Friction-induced electrical signals generated during the experiments were collected, and their variation patterns throughout the running-in and wear processes were analyzed. Results indicate that during the running-in and wear process, triboelectric signals and friction coefficients exhibit consistent variation patterns, namely a transition from high values to a final stable state. During the running-in stage, both current values and friction coefficients are high, with electrical signal waveforms exhibiting distinct sinusoidal characteristics and probability density functions presenting bimodal curves. During the stable wear phase, both current values and friction coefficients were smaller and stable. The electrical signal waveform exhibited random distribution, and its probability density function was unimodal. Therefore, triboelectric signals can be used to characterize the running-in and wear process.