Study On The Influence Of Surface Integrity Parameters On Gear Elastoplastic Contact Performance

Gear is one of the most important industrial components,of which performance directly determines the service life,safety and reliability of equipment.The development of modern machinery brings severe challenges to loading capacity and fatigue life of gear,and takes gear contact fatigue problem to an increasingly prominent situation.The complex profile and rolling-sliding motion lead to intricate kinematic behavior.The high localized pressure is caused by the interaction between roughness and lubricant on the teeth surface.The complex multiaxial stress state suing meshing process takes to the typical high-cycle and multiaxial contact fatigue.The current computing method of gear contact fatigue life is based on Hertzian theory.The performance of interface mechanics,the effect of surface integrity and the evolution material properties are simplified,which lose the sight of topography evolution and material deterioration.This research develops a gear plasto-elastohydrodynamic lubrication model incorporating kinematic behavior,surface topography,lubricant characteristics and material gradient properties.The contact fatigue experiments are performed using rolling-sliding contact test rig.Contact fatigue failure mechanism of gear is investigated,which supports the development of modern anti-fatigue design system of gear.The specific contacts are as follows:（1）The time dependent surface velocity,equivalent radius of curvature and contact force are calculated based on the geometric and kinematic analysis.The lubrication govern equations is developed using general Reynolds equation.The surface plastic deformation and load-induced residual stress is solved by semi-analytical method（SAM）,and plastic strain is calculated with J₂ flow rule.The elastoplastic contact and hydrodynamic lubrication approach are coupled by film thickness equation.Gear contact characteristics is investigated through the developed plasto-elastohydrodynamic lubrication model.（2）Gear hardness gradient,initial residual stress and tooth surface topography is measured and numerically represented.The critical plane based multiaxial fatigue criterion is applied to evaluate gear contact fatigue.The influence of surface hardness,effective case depth and surface roughness on the contact fatigue performance is investigated.（3）The rolling-sliding contact is simulated considering the evolution of surface topography.The stress history during loading passages is obtained,and the stress micro-cycles are extracted using Rainflow counting method.The influences of surface speed,slide-to-roll ratio and roughness on surface fatigue damage in evaluated.（4）Contact fatigue experiments are performed using rolling-sliding contact test rig.Surface topography,fatigue damage and sub-surface cracks is observed and recorded.Micropitting area ratio and wear volume is calculated based on the image recognition technique.The contact fatigue life,micropitting and mild wear under rolling-sliding are investigated.The gear contact fatigue model under plasto-elastohydrodynamic lubrication is developed in this work.The effects of gear hardness gradient,residual stress and surface topography on contact fatigue performance are discussed.The influences of stress micro-cycles and topography evolution on surface fatigue damage are investigated.The relation between fatigue failure and work conditions,such as slide-to-roll ratio,film thickness ratio and load,is studied based on rolling-sliding contact fatigue test.This work contributes to the further understanding of the mechanism of fatigue failure and the development of modern anti-fatigue design system of gear.