We report a complete experimental study and a physical modelling of the long-term evolution of the main electrical properties of a metal ring/wire sliding contact, the wire, and the ring being coated with a thin Au film. The long-term evolution of the Au/Au sliding contact was characterized through the measurement and tracking of relevant quantities such as the voltage noise across the contact, revealing the ageing of the contact. A phenomenological approach to the sliding contact, coupling both electrical and mechanical aspects, allows a sensible interpretation of the experimental results. This approach retains three contributions to the voltage noise operating at different scales, namely the rings surface geometry, chemical composition fluctuations of the coated rings, and the mesoscopic structure of the contact. A fundamental distinction between these sources is established, owing to their effects relying on either the mechanical contact losses or resistance fluctuations. We finally show that the determination and tracking of these noise sources using reasonable specific indexes lead to reliable criterions of the electrical contact quality.

In some industrial devices the use of a sliding contact to transmit power currents or communications signals is required. The physical and especially the tribological understanding of these electromechanical systems is therefore a major issue. Thus, we report a theoretical and numerical study accounting for the mechanical influences about the electric transport properties of a sliding metallic dry contact and of their variations with the sliding speed and the contact load. We characterize these variations by analyzing the voltage noise across the contact during sliding. Results are compared to experimental data, and show a good agreement between theory and experiments below a critical speed value. This study is part of the research and the development about tribology and dynamical interfaces monitoring.

This study presents a robust methodology for analyzing 3D roughness parameters to characterize sandblasted surfaces, identifying the most relevant descriptors for process optimization. Sandblasting with irregularly shaped corundum particles is performed using five grit sizes (25, 50, 90, 125, and 250 µm) and three pressure levels (2, 3, and 4 bar). The resulting surfaces are characterized through eight 3D roughness parameters: Sa, Spc, Sal, Sfd, Sdq, Sdr, Spd, and Str. A linear model of the form Q = a + b.D + d.D.P, where Q represents the roughness parameter, D is the average grit size, and P is the sandblasting pressure, is employed. For Spd, a nonlinear model, Spd = (a + b.D + d.D.P)², yields a significantly improved determination coefficient, demonstrating the model’s enhanced ability to capture the complexity of the Spd parameter. The double-bootstrap analysis validates the statistical significance of all models, providing confidence intervals for each parameter. This approach emphasizes the importance of advanced 3D roughness descriptors for accurately analyzing surface textures in sandblasting processes, offering a reliable framework for surface characterization and industrial optimization.

Vibrational analysis is one of the usual methods to monitor rotational machines that uses sensors fixed on the frame. Although effective, this method can be expansive and uneasy to use particularly at slow speeds (<60 rpm). This paper offers to evaluate the capabilities of a 6-axes low-cost inertial measurement unit which is positioned on the shaft to detect and diagnose bearing defects. This study is based on experimental data allowing to (i) choose the most relevant axis for better defect detection, (ii) to compare statistical indexes using usual vibratory analysis for a speed range from 5 to 400 rpm and for five defect severities, (iii) to compute the defect severity from a shocks local study.

The present work focuses on the using of an inertial measurement unit (IMU) to monitor the signatures of defects in ball bearings under stationary and non-stationary regimes. The present paper completes the existing literature for both regimes by (i) investigating the influence of IMU parameters on signals derived from six axes and by (ii) proposing signal processing methodologies to detect defects in outer and inner rings. Defects are both declined on the inner and outer rings in five severities, and are studied at six rotation speeds (5 rpm to 400 rpm) and five radial loads (100 kg to 500 kg). Detection and diagnostic were made qualitatively and summarize in tables. Two different methods for processing the non-stationary regime signals are compared. Our results open new ways on the improvement of inertial units and their application.