Finite Element Analysis Of Spur And Helical Gears

As one of the fundamental components,gears are widely used in various applications due to its precision transmission,high reliability,and compact structure,mature manufacturing processes,etc.However,due to the rapid development of modern technology,such as high-speed railway,the gear transmission develops toward heavy load,high speed,high precision,low noise and high life expectancy,which demands the deep understanding of gear failures.As a successful analysis method,finite element method is widely applied in various stress related analysis.The design of an effective and reliable gearing system includes its ability to withstand root bending stress(RBS)and surface contact stress(SCS).Various research methods such as theoretical,numerical and experimental have been adopted throughout the years,however,theoretical and numerical methods are specially preferred as experimental testing may be much expensive.So many researchers have utilized FEM to predict RBS and SCS.This thesis conducts the analysis of micro-pitting mechanism of gear based on Finite Element Method(FEM).Contact pressure,subsurface stress,and relative velocity of involute spur and helical gears teeth in meshing are studied with the consideration of friction coefficient effects.The main contents and conclusions are as follows:Finite element models of gears are built based on three-dimensional solid model and proper finite element and mesh structure are determined.The changes of normal force,contact pressure,and subsurface stresses are explored during the meshing process.The results show that normal force,contact pressure,and subsurface stress increase first during approach process,then get maximal near the pitch point,and finally decrease during the recess process.Helical gear shows much successive change of normal force and subsurface stress,which promote preferred performance.The effect of friction coefficient on the contact performance of gear is investigated.It can be found that the increase of friction coefficient will elevate the contact stress and make the maximum subsurface stress move up to the surface,which implies that lubrication performance of gear should be paid much attention during the gear design process.Comparing with the traditional design methods based on Lewis formula for bending stress and Hertz equation for contact stress,the FE analysis can obtain the comprehensive information such as three dimensional stress distribution,etc,which is of importance for high-quality gear design and analysis.Based on these FEM results,the structure deformation of tooth can also be obtained,which will be fundamental information for the future research on the effect of tooth deformation on the lubrication performance.