Experimental Heat Transfer and Contact Area Analysis in Large-Diameter Slewing Ring Thrust Ball Bearings Using a Linear Model Mock-Up Bearing

Abstract

Abstract. Understanding heat transfer behavior in large-diameter slewing ring thrust ball bearings is critical for ensuring reliable operation in high-temperature environments, such as nuclear reactors. This study develops a unique experimental setup utilizing a linear model mock-up bearing (LMMB), a simplified segment representing the full slewing ring bearing, to investigate thermal contact resistance (TCR) across bearing interfaces. An electric coil heats the bottom raceway, while the top raceway is exposed to ambient conditions. K-type thermocouples placed at six key interfaces capture the temperature profile under varying mechanical loads applied to the top raceway. Results reveal that TCR decreases notably with increased load due to an expanding real contact area between the balls and raceways. However, it tends to saturate beyond approximately 40 kN, despite further increases in Hertzian contact area. Finite element analysis (FEA) produced temperature distributions that showed good qualitative agreement with the experimental measurements. The study highlights the nonlinear behavior of thermal contact area with load and clarifies the conditions under which classical Hertzian assumptions diverge from real thermal behavior. These findings provide a useful experimental basis for improving thermal assessment of slewing ring thrust bearings operating under prolonged high-temperature and high-load conditions in nuclear reactor environments.