PSI - Issue 81

Andrii Gypka et al. / Procedia Structural Integrity 81 (2026) 478–485

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tribological contacts. Moreover, existing diagnostic methods do not allow timely detection of the initial stages of degradation of protective surface layers, which is critically important for preventing the transition to severe volumetric material destruction. Recent research highlights the promising potential of electrophysical monitoring techniques for friction and wear processes, particularly the measurement of contact electrical resistance (CER) of tribological pairs. This method enables real-time assessment of the structural condition of friction surfaces (presence and type of DSS), identification of operating ranges of normal friction and wear, and significant reduction of experimental testing time. Therefore, there is a growing need to develop and implement an integrated methodology for CER measurement that would provide express and objective evaluation of friction and wear processes, the kinetics of DSS formation, transformation, and failure, as well as determination of optimal (minimum) values of key tribological performance parameters. Solving this issue will contribute to improving the reliability and operational efficiency of tribotechnical systems, optimizing their maintenance and repair processes, enhancing the development of wear-resistant materials for tribocouples, expanding tribological databases, and enabling effective control strategies for processes occurring within frictional contact zones. Ensuring high tribological reliability of friction units in modern transport and industrial machinery is a key challenge due to the complexity of wear mechanisms and the influence of lubrication and surface microstructure on service life Aulin (2024). Traditional approaches for evaluating friction and wear processes rely mainly on mechanical indicators such as wear rate and friction coefficient, which often do not fully reflect structural transformations occurring directly in the frictional contact zone Beake (2021), Cai (2024). In recent years, numerous studies have shown that electrical parameters, particularly electrical/contact resistance (ECR/CER), are highly sensitive to the condition of the contact interface, oxide film formation, tribochemical reactions, and lubrication modes Chen (2020) Jackson (2022), Januszewski (2023), Kovtun (2023). This makes CER a promising diagnostic parameter for the real time identification of transitions between running-in, stable mechano-chemical or thermo-chemical wear, and catastrophic damage regimes Kreivaitis (2025), Liu (2020), Mei (2021). At the same time, the search for optimal material combinations (steel – steel, bronze – steel, composite contacts), lubricants (diesel fuel, oils, ionic liquids) and additives with improved antifriction properties remains critical for minimizing energy losses and extending the durability of machine components Ustymenko (2021), Liu(2020), Wu (2024), Zhao (2024), Zhou (2024). Therefore, comprehensive tribological studies that integrate simultaneous measurement of CER, friction coefficient, wear, and structural state of surfaces are highly relevant and continue to gain wide attention in the scientific community. The aim of this research is to conduct a comprehensive set of investigations to validate the effectiveness of using the contact electrical resistance (CER, R ) parameter for rapid assessment of the kinetics of changes in key tribological performance indicators and for determining the optimal (minimal) operational ranges of these parameters. The study targets the evaluation of the structural condition of friction surfaces of tribocouple components as load parameters vary across different materials and lubricating environments. Additionally, the objective is to substantiate the need for designing and manufacturing a universal friction testing machine capable of smooth variation of load parameters over wide ranges, featuring increased stiffness of both the tribological assembly and loading mechanism. The research includes experimental studies on the influence of sliding speed V and contact pressure P on the behavior of the main tribotechnical parameters, CER ( R ), and the structural conditions of the friction surfaces of the tested tribocouples under different material combinations and lubricating media, aimed at identifying correlations between these characteristics. A rapid diagnostic method is developed and validated to determine the ranges and levels of normal mechano- and thermochemical friction and wear processes, as well as critical transition points between run-in, normal wear, and catastrophic bulk destruction regimes, based on CER ( R ) measurements. 2. Research Results In accordance with the stated aim and research objectives, the experimental investigations were carried out using a specially designed and manufactured friction testing machine featuring increased stiffness of its main structural assemblies and extended ranges of smoothly variable loading parameters applied to the tribological pair. The enhanced rigidity of the machine frame, friction unit, and loading mechanism minimizes the occurrence of vibrations during testing and, consequently, their negative influence on the accuracy and reliability of the obtained results. The general view of the friction testing machine and friction unit is shown in Fig. 1. The tribological contact consists of two elements: the tested specimen in the form of a cylindrical pin with a flat end-face friction surface, and the counter-specimen in the form of a disk with an outer cylindrical friction surface. Both components were manufactured according to the 6th accuracy grade. The surface roughness of the friction interfaces after the running-in stage was R Z =0.125 – 0.250 μm