Lubricated Loaded Tooth Contact Analysis (LLTCA) for Spur Gear Pairs

Gears are key components in the operation of many machines and mechanisms. However, their presence often affects system efficiency and can lead to noise, vibration and harshness (NVH) issues. Therefore, improved efficiency and NVH refinement are the major drivers in the development of gearing systems. These requirements lead to significant effort expended in the design of optimum gear pairs and their lubrication. Currently available analytical and numerical gear analyses are limited to simplified methods such as dry contact conditions, use of basic classical Hertzian contact theory and finite element analysis in tooth contact analysis (TCA). Thus, the generation of more complex models would enhance the representation of gear interactions, including with lubricated contact analysis. Tooth Contact Analysis (TCA) is usually the first step for an in-depth gear efficiency, NVH and durability analyses. Those TCA methods described in open literature study the teeth pair contacts, mostly neglecting the effect of lubrication. In reality, contact mechanics and lubrication are closely inter-linked, requiring an integrated approach. This paper outlines a combined FEA-based TCA model with a lubricated contact mechanics analysis of real gear pairs, thus improving gear pair efficiency, NVH and durability predictions. An initial dry gear analysis with an estimated constant coefficient of friction in the contact is carried out. The results of this initial analysis provide input data for a subsequent tribological model in order to generate improved estimates of the contact friction for a new TCA. This approach leads to the integration of TCA and lubrication in an iterative manner. The gear pair geometry is measured using a Coordinate Measuring Machine (CMM) which takes into account manufacturing imperfections and real geometry within its measurement sensitivity of ±1.5 μm. This data is used in the TCA analysis.