The Research For Coupling Of Wear Damage And Fatigue Damage To Gear Transmission

Wear damage and fatigue damage are usual damage forms in engineering practice.These two forms of damage were often studied respectively in the past and single damage was set as precondition and background for part check and design.However,wear damage and fatigue damage usually exist on a contact surface at the same time in engineering practice and the relationship between these two forms of damage is not superposition,but interaction in a form of coupling damage.As a kind of widely used mechanical component,the damage process of gear is always the research direction of many researchers.Wear damage and fatigue damage exist on tooth surface simultaneously when gears are engaging.As a result,the research aims at the coupling damage of wear and fatigue on profile shifted gear.The major research is as follows:(1)Research about wear damage of tooth surface.The widely used Archard formula as theoretical basis is deformed as form of wear depth.The engaging process is numerically simulated through MATLAB program to get the parameters of each meshing point.Then the parameters are substituted into the deformed Archard formula to get the wear depth of each meshing point after a single engaging process.The difference of wear damage on various positions is apparent.The wear damage of the position near pitch line is serious,and the wear damage of the position far away from pitch line is slight.The enlargement of torgue could aggravate wear damage on tooth surface,and the enlargement of rotate speed has no influence on wear damage.(2)The process of tooth surface’s fatigue damage is studied from the point of fracture mechanics.Select four meshing points from drive gear and four meshing points from driven gear to study their fatigue damage.Discretize the process of engaging and use ABAQUS to solve the stress intensity factor of crack tips to get the fatigue cracks’ extension velocity and extension direction in every extension phase.It is seen as fatigue failure to the meshing point when fatigue cracks extend to tooth surface.In the same fatigue crack,the extension rate of the crack tip pointing to root is faster than the crack tip pointing to tooth crest.The position near pitch line happen to fatigue failure at the earliest.(3)The coupling of wear damage and fatigue damage.Consider the meshing points’ wear rate into every extension phase of fatigue cracks to get the wear depth of the meshing points in every extension phase.Update the position of fatigue cracks after every extension phase through ABAQUS.It is seen as fatigue failure in coupling damage to the meshing point when fatigue cracks extend to tooth surface.On the position where wear rate is faster than crack extension rate,wear damage will restrain the occurrence of fatigue failure.On the position where crack extension rate is faster than wear rate,wear damage will promote the occurrence of fatigue failure.(4)The improvement of check and design formula of gear’s contact fatigue strength.Because of the continuous action of wear damage,the material of tooth surface is removed off continuously,which result in the decrease of radius of curvature of the meshing point.Consider the effect of wear damage into traditional check and design formula of gear’s contact fatigue strength.The radius of curvature of the meshing point minus the wear depth in design lifetime and combine the Archard formula to get the check and design formula of gear’s contact fatigue strength considering wear damage.In the same condition,the contact stress on tooth surface considering wear damage is larger than the contact stress through traditional method,and the fatigue life is shorter.