Occlusion failure analysis and optimization design for steel piston pin hole-pin friction pair

Abstract

The focus of the present study was on the D25TCIF steel piston, and the underlying causes of pin hole occlusion failure were systematically analyzed. The investigation considered factors such as heat transfer, mechanics, lubrication, material properties, and forging processes. Additionally, an optimization strategy was introduced based on the cause of the failure to reduce the risk of occlusion failure of the pin hole. At the same time, the influence of the structural parameters of the connecting rod small head on the lubrication performance of the pin hole bearing was investigated, providing a theoretical basis for the matching design of the structural parameters of the double friction pair of the piston pin bearing. The findings indicate that the primary cause of pin hole occlusion failure in steel pistons is the concentration of thermo-mechanical coupling stresses and elevated temperatures within the pin hole. This condition results in the rupture of the lubricating oil film in the pin hole bearing, leading to dry friction between the piston pin and the bearing surface. The optimization method designed in the present study enhanced the minimum oil film thickness of the pin hole bearing from 0.354 μm to 0.377 μm, reflecting an increase of 6.50 %. Additionally, the minimum oil film thickness of the small head bearing was improved from 0.599 μm to 0.691 μm, corresponding to a 15.36 % increase compared to the original configuration. Meanwhile, the optimization method predicted a minimum oil film thickness of 0.382 μm for pin hole bearings and 0.693 μm for small-head bearings, with a relative error of less than 5 % from the simulated values. Such findings demonstrate that the optimization method has a good optimization effect and accurate prediction. This approach offers novel insights for the development of future solutions to address the failure of steel pistons in engineering applications.