Development of highly durable thin-film sensors for studying pressure and temperature distribution in contacts under mixed friction

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Lubricated sliding contacts play a decisive role in ensuring the function of almost any technical system with mechanical components. Lubrication failure leads to damage of the involved contact partners often followed by downtime and costly repairs. While the mechanisms of hydrodynamics and elastohydrodynamics (EHD) are well understood and scientifically explained, research on boundary friction and mixed friction conditions is still in its beginning, in spite of numerous related research activities carried out in the past. There are specific research works regarding the theoretical explanation and simulation of mixed friction conditions, however, its experimental validation fails due to the absence of suitable measurement methods. Especially for the measurement of local temperatures and pressures in mixed friction contacts, there are no suitable sensors available.Hence, the objective of the proposed research project is the extension of the field of application of thin-film sensors already successfully applied within research on elastohydrodynamics, in order to enable a measurement under mixed friction conditions with temporary contact between the partners and the resulting high loads.Therefore, wear resistance and adhesive strength of the sensor layers are to be improved. Within this research project, it will be studied whether the required improvement can be realized by means of electrically insulating diamond-like amorphous carbon-based layer systems (materials: a-C, a-C:H, ta-C, ta-C:H, CBNC; layer concepts: single, multi and gradient layer). High adhesive strength, hardness, thermal conductivity, chemical resistivity, as well as a high variability of the physical properties are prominent attributes of these layers.Furthermore, sensor layout and geometry applied in elastohydrodynamic contacts, have to be optimized for mixed friction conditions. While in EHD line contacts sensors with elongated measuring points can be used, in contacts under mixed friction sensors with almost punctiform measuring points are needed. The new sensor systems will be validated with one of the journal bearing test benches at IPEK.By means of measuring pressure and temperature distribution in mixed friction contacts, both understanding of tribological interrelations can be deepened as well as corresponding models can be verified.