Master's Dissertation
DOI
Document
Author
Full name
Arnaldo Oliveira Lima
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2019
Supervisor
Committee
Rego, Ronnie Rodrigo
Silva, Carlos Henrique da
Title in Portuguese
Método numérico para determinação do coeficiente de atrito ao longo da superfí­cie em contato lubrificado.
Keywords in Portuguese
Atrito
Engrenagens
Método dos elementos finitos
Abstract in Portuguese
Title in English
Numerical method for the evaluation of the coefficient of friction along the surface in lubricated contacts.
Keywords in English
Coefficient of friction
Finite Element method
Lubricated contacts
Roughness
Stribeck curve
Abstract in English
The efficiency of mechanical systems is influenced directly by the local friction coefficient, which is related to the lubrication regimes. The coefficient of friction can be studied using the finite element method (FEM) to replace experimental tests and reduce analysis time. This dissertation had the objective to develop a methodology to evaluate the coefficient of friction in a tribological pair and the effect on the efficiency by numerical simulation. In this model, a system composed of a pair of helical gears was defined. In a first analysis, the AVL Excite Power Unit software was used, which uses the tool MBD (Multi-Body Dynamic), enabling the simulation of the transmission with the main elements in a 1D model, which takes into account the theory of elastohydrodynamic lubrication (EHL). The Abaqus® software was used to create a 3D model, which considers the pair of helical gear and a developed subroutine for application of the literature lubrication model. In all simulations, the conditions of operation of a rig tests and three different surface finishes of the gear teeth were considered, depending on the manufacturing process: milling, grinding and polishing. Besides the roughness, the effect of angular velocity on the losses of the system was evaluated. The 3D model was compared with the 1D model and with the results of rig tests efficiency. The 3D model allowed to evaluate the coefficient of local friction in the contact line of the tooth. Higher angular velocities increased the film specific thickness, thus reducing the coefficient of friction and promoting an improvement in the efficiency of the system. The lowest values of coefficient of friction are in the region of the primitive diameter, there the SRR is zero. The angular velocity influenced more than the roughness. The analyzes of the 1D and 3D models indicated that the 1D model overestimates the transmission efficiency, while the 3D model presented results compatible with the rig tests.