Energy efficiency and functional reliability are the two key requirements in the design of high-performance transmissions. Therefore, a representative analysis replicating real operating conditions is essential. This paper presents the thermoelastohydrodynamic lubrication (TEHL) of meshing spur gear teeth of high-performance racing transmission systems, where high generated contact pressures and lubricant shear lead to non-Newtonian traction. The determination of the input contact geometry of meshing pairs as well as contact kinematics are essential steps for representative TEHL. These are incorporated in the current analysis through the use of Lubricated Loaded Tooth Contact Analysis (LLTCA), which is far more realistic than the traditional Tooth Contact Analysis (TCA). In addition, the effects of lubricant and flash surface temperature rise of contacting pairs, leading to the thermal thinning of lubricant, are taken into account using a thermal network model. Furthermore, high-speed contact kinematics lead to shear thinning of the lubricant and reduce the film thickness under non-Newtonian traction. This comprehensive approach based on established TEHL analysis, particularly including the effect of LLTCA on the TEHL of spur gears, has not hitherto been reported in literature.
This paper presents a brief review of elastohydrodynamic analysis in commemoration of the immense contributions of Duncan Dowson. This paper also presents an elastohydrodynamic analysis of the elliptical point contact problem under steady state as well as transient conditions. The overall methodology is validated against numerical predictions and experimental observations of acknowledged historical sources. The validated methodology is used to make original contributions in the elastohydrodynamics of elliptical point contact subjected to complex combined contact kinematics, including rolling/sliding, mutual convergence and separation (squeeze film motion) of contacting pairs, when subjected to reciprocating and spinning motions. This combined complex contact kinematics under transient conditions has not hitherto been reported in the literature. This paper shows the critical role of squeeze film motion upon lubricant film thickness. The results also show that the influence of spin motion is only significant at fairly high values of angular velocity and in the absence of a rolling/sliding motion.
Gears are key components to 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 efforts expended in the design of optimised gear pairs and their lubrication. Analytical and numerical gear analysis methods 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 represent gear interactions, including lubricated contact analysis more realistically. Tooth Contact Analysis (TCA) is usually the first step for an in-depth; gear efficiency, NVH and durability analysis. Analyses described in open literature study tooth contact 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 for real gear pairs, thus improving the prediction of gear pair efficiency, NVH and durability. 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.
Meshing teeth pairs of involute spur gears often form the final drive of high-performance motorsport transmissions. They are subject to high normal and shear loading. Under transient conditions pertaining to a meshing cycle, the contact conditions alter from the onset of teeth pair engagement through to maximum normal loading, followed by contact separation. Sliding motion only ceases instantaneously at the pitch point. The regime of lubrication remains mostly in non-Newtonian thermo-elastohydrodynamic conditions. The results show that a starved inlet boundary is attained throughout most of the meshing cycle which leads to the diminution of the pressure spike at the exit from the contact conjunction. The reversing sub-surface shear stresses are the main source of the onset of any inelastic deformation, which is dominated by the primary pressure peak in compliance with the Hertzian maximum pressure. The shear stress field is supplemented by an induced field due to the presence of the pressure spike. Under starved conditions this secondary stress field is diminished. The combined solution of elastohydrodynamics with a thermal network model, non-Newtonian lubricant traction, and sub-surface stress evaluation provides for a comprehensive solution not hitherto reported in the literature.
Gears are key components to 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 efforts expended in the design of optimised gear pairs and their lubrication. Analytical and numerical gear analysis methods 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 represent gear interactions, including lubricated contact analysis more realistically. Tooth Contact Analysis (TCA) is usually the first step for an in-depth; gear efficiency, NVH and durability analysis. Analyses described in open literature study tooth contact 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 for real gear pairs, thus improving the prediction of gear pair efficiency, NVH and durability. 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.
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