Mechanisms of heat generation and transport into contacting solids under mixed thermal elastohydrodynamic lubrication

Heat generation and transfer in mixed thermal elastohydrodynamic lubrication (TEHL) contacts control lubricant behaviour, but temperature extrema alone cannot distinguish energy-source contributions from the depth and extent of solid heating. This study combines a fully coupled mixed EHL model with three-dimensional energy equations for the lubricant and both solids to model rough finite line contacts. A set of source-to-solid indicators quantifies pressure-related work, viscous shear dissipation, asperity frictional heating, lubricant-solid interfacial heat transfer, thermal penetration depth and thermally affected volume. The lubrication response is assessed against rough line-contact traction experiments, yielding an average relative error of 11.36%; the thermal indicators remain numerical predictions. Across four load-speed cases, viscous shear dissipation accounts for over 98% of irreversible heat generation. The ratio of heat conducted into both solids to irreversible heat generation is 99.5–99.8% in the low-load cases, but decreases to 47.1% and 7.9% at high load. With a 5% local interfacial-temperature-rise criterion, the normalised penetration depth is 44.0–87.1% in the lower solid and 64.0–90.5% in the upper solid. The affected-volume fractions are 6.2–14.9% and 10.6–21.6%, respectively. Within the investigated cases, higher load increases the dimensional depth and volume of heating, whereas higher speed raises the peak temperature but reduces both measures through stronger streamwise advection and shorter effective exposure. The proposed indicators quantify energy conversion, interfacial transfer and subsurface heat propagation in mixed TEHL contacts.