Finite Element Based Surface Fatigue Estimation in Involute Spur Gear under Rolling Sliding Contact Conditions
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Date
2011-10
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Addis Ababa University
Abstract
There are two main factors that affect the service life of gears: surface durability and
tooth bending strength. Pitting and scoring is a phenomenon in which small particles are
removed from the surface of the tooth due to the high contact stresses that are present
between mating teeth. After the investigation of shot pinning to increase the tooth
bending strength in gears, surface durability, in the form of macro and micropitting, is
now considered the dominant restriction on gear life and performance. The main
objective of this thesis is to develop a method for the investigation of surface fatigue in
involute spur gears using finite element analysis. In achieving this two-dimensional &
three- dimensional equivalent contacting cylinders to model involute spur gear in contact
and three- dimensional model of involute spur gear is used. Modeling of involutes spur
gear to study contact stress under different working conditions using CATIA & ANSYS
software is done. In addition parametric study to investigate the effect of loading
condition and material types in contact stress in gears, estimation of surface fatigue in
rolling-sliding contact condition in spur gear by finite element method using ANSYS
Workbench software, effect of initial surface roughness on surface fatigue is studied. The
results obtained are compared with analytical method. Results from FEA using ANSYS
show that, a 2D model, estimates accurately contact pressure and stresses bellow the
contacting surface, where as the 3D Model estimate contact pressure with reasonable
accuracy and failed to estimate stresses bellow the contacting surface. Results from
ANSYS Workbench, for a 3D model of involute spur gear, shows that contact stress and
shear stress results, correlated with theoretical formulation, with tolerable accuracy but,
failed to estimate von-Mises stress with acceptable accuracy. Results from ANSYS
Workbench, for a 3D model of equivalent contacting cylinders, show that contact stress,
von-Mises stress and shear stress results, correlated with theoretical formulation, with
tolerable accuracy. Finally, in estimating surface fatigue, this paper verified that, as the
surface roughness increases the minimum fatigue life and the load caring capacity for a
specific design life decreases.
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Mechanical Design Stream