In this research, we utilized machine learning (ML) algorithms to predict the friction torque and friction coefficient in a statically loaded radial journal bearing. The study investigated the ...influence of temperature, bearing load, and rotational speed on the variation in friction torque and friction coefficient. Three different ML algorithms, namely, Artificial Neural Network (ANN), Support Vector Machine (SVM), and Regression Trees (RT), were applied to experimental tribological data. Performance assessment demonstrated that ML-based models can successfully predict the variation of friction torque and friction coefficient. Furthermore, we conducted a comparative analysis to evaluate the performance of ML-based models in relation to each other. The results of this study have useful implications for the design and optimization of statically loaded radial journal bearings.
Carbon friction linings are increasingly being used for clutches in industrial applications because of their excellent properties in terms of friction behavior, temperature resistance, and wear. Due ...to safety-relevant use of these clutches, their failure must be avoided and thus the damage behavior must be investigated. In this article, the spontaneous damage behavior of two multi-plate clutches (FS1, FS2) with different carbon friction linings (a woven and a composite carbon friction lining) is investigated experimentally. For this purpose, the mechanical load was increased step by step in step tests with brake shifting and the damage progression was documented by regular dismounting of the clutch. For the FS1 friction system with a composite carbon friction lining, the initial damage was local discoloration of the steel plates due to oil cracking products. The failure of the system occurred in friction system 1 due to shrinkage of the steel plates on the inner carrier. For the FS2 friction system with a woven carbon friction lining, the initial damage was also discoloration of the steel plate. With increasing load there was displacement of the friction lining pads. The failure of the system was caused by the detachment of the friction lining from the carrier plate. The research results highlight the potential for improvement of the multi-plate clutch in terms of a more temperature-resistant adhesive layer between the carrier plate and the friction lining. In addition, the steel plates must be heated evenly in the radial direction, which can be achieved by optimizing the geometry.
Over the last decade, researchers have explored an intriguing polymer composite composed of granular polytetrafluoroethylene (PTFE) 7C and alumina particles. This material is extraordinary because a ...very small amount of alumina additive (<5 wt%) decreased the wear rate of the PTFE composite by over four orders of magnitude. Previous studies have shown that this wear resistance was initiated and maintained by the formation of a stable, robust, and uniform polymeric transfer film on the surface of the countersample. Although its importance to this tribological system is clear, the transfer film itself has not been well understood. Careful spectroscopic analysis throughout the stages of transfer film development revealed that tribochemistry plays a major role in the significant wear rate reductions achieved in PTFE and alumina composites. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy reveal that PTFE chains break due to the mechanical stresses at the wear surface and, in the presence of oxygen and water in the ambient environment, produce carboxylic acid end groups. These carboxylic acid end groups can chelate to the exposed metal on the steel surface and nucleate the formation of the transfer film. The resulting thin and robust fluoropolymer transfer film protects the surface of the steel and changes the sliding interface from polymer on steel to polymer on polymer transfer film. These effects keep friction coefficients and wear rates low and stable. Ultimately, the real mechanisms responsible for the exceptional wear performance of these materials are all about the tribochemistry.
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