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Title: Lubricated contact analysis of a spur gear pair with dynamic loads
Author: Liu, Huaiju
ISNI:       0000 0004 2744 5384
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2013
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In the present research study, a comprehensive spur gear lubrication analysis has been carried out to understand the gear contact behaviour under lubrication conditions. The modelling works have been extended to consider the effects of thermal mechanical, non-Newtonian fluid, surface roughness, transient squeeze and dynamic load conditions. First, the elastohydrodynamic lubrication theory is studied and relevant numerical approaches are introduced. The reduced Reynolds equation technique is applied to deal with any potential "asperity contacts" or any other ultra-thin film situations. Those situations could be a result of the surface roughness or the dynamic load effect. This approach allows us to capture local information about pressure, traction, film thickness, etc., within the nominal contact zone. Influence of working conditions, i.e. load, rolling speed, as well as the sliding to roll ratio are discussed with those models (Newtonian or non-Newtonian fluids, isothermal or thermal conditions). The non-Newtonian fluid effect has been investigated with a Ree-Eyring fluid model and a power-law fluid model and the thermal effect is studied by solving energy equations of interacting solids and the film numerically with the sequential sweeping technique. The dynamic effect on contact performance is also studied. The dynamic load is calculated using a two degree-of-freedom lumped parameter system dynamic model in which the varying mesh stiffness is considered as the excitation. The dynamic model is solved using the Runge-Kutta method. The effects of the dynamic load effect on pressure distribution and film thickness in a whole mesh period are discussed. The normal contact stiffness of a spur gear pair is also predicted based on the deterministic tribology models. The main contributions from the present research could be summarized as follows: i. An elastohydrodynamic lubrication model for a spur gear pair is developed by taking into account the effects of transient squeeze, the non-Newtonian fluid, the rough surface and the thermal mechanical contacts which makes the proposed model one of the most advanced models currently evaluating gear lubrication performance. This model can also be applied to bearings, cams, or other gear types with some modifications. ii. The friction behaviour, which is not investigated as extensively as the film thickness in existing work, is studied. The effects of the working conditions (the load, the rolling speed, the slide/roll ratio), the non-Newtonian conditions, the rough surface conditions, as well as the thermal conditions on friction behaviour are discussed. The conclusions suggest controlling surface topography patterns and working conditions aiming at a reduced friction coefficient and a longer service life. iii. The dynamic effect on lubrication performance and effect of lubrication on normal contact stiffness of a spur gear pair are studied. The work provides a potential gateway for a more comprehensive evaluation of spur gear pair working performance using a tribology-dynamic coupled method which is the next area this author would like to explore.
Supervisor: Not available Sponsor: School of Engineering, University of Warwick ; China Scholarship Council (CSC)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TA Engineering (General). Civil engineering (General) ; TJ Mechanical engineering and machinery