Calculation Methods Of Adhesive Wear And Contact Fatigue Life For Shot-peened Gear

The requirements of the high-end equipment manufacturing industry for the comprehensive performance of gear are more and more demanding.Adhesive wear and contact fatigue break are the major forms of gear failure.In order to improve the comprehensive performance of the tooth surface,various gear strengthening processes have been developed.Shot peening is an important cold-working process to enhance the fatigue strength of gear,which has been rapidly promoted and widely used in recently years because of the advantages of low cost and high productivity.In this paper,through the experiment and numerical simulation of the shot peening,the effect of shot peening on the comprehensive performance of 45 steel is investigated.Afterwards,the results induced by shot peening are applied in spur gear,and the influence of shot peening on gear wear or contact fatigue is analyzed respectively via the mixed elastohydrodynamic lubrication or the proposed contact fatigue life calculation method for spur gear,which provide some forward guidance and theory basis for shot peening treatment of gear.The main research contents as follows:The shot peening experiment of 45 steel gear specimen is studied.Through the shot peening treatment for 45 steel specimens without carburizing and quenching,residual stress and surface performance of the specimens before and after shot peening were compared respectively.The results indicate that the surface roughness and hardness of the specimen have been greatly improved after peening treatment,and the residual stress on the subsurface have been transforme d from tensile stress to compressive stress which is beneficial for improve fatigue life.The simulation model of shot peening is established and calculated.The presented FEM-DEM coupling method was testified by comparing the predicted residual stress and surface roughness with measurements.Based on the verified model,the effects of surface coverage,shot peening intensity and shot size on the residual stress and surface roughness are analyzed further.The results show that the peak value of compressive residual stress and surface roughness increase with increasing surface coverage or shot peening intensity.However,when the target surface achieve full coverage,shot peening intensity has an important effect on the peak value of compressive residual stre ss and surface roughness.Under the same conditions,smaller shot can increase the peak value of compressive residual stress,while larger shot is beneficial to increase the thickness of compressive residual stress layer and reduce the surface roughness.The wear depth is calculated for the shot-peened gear.Under the mixed elastohydrodynamic lubrication,the gear wear model considering contact temperature is established.Combined with the measured surface roughness and hardness,the wear depth of gear before and after peening treatment is calculated,and the effect of shot peening on the adhesive wear is investigated.It is found that since the specimen is not carburized and quenched,the hardness is low,and the surface roughness after shot peening is greatly increased,which results in an increase in the wear depth.The contact fatigue life is calculated for the shot-peened gear.According to the model for spur gear contact analysis and the Matake multiaxial fatigue criteria,a contact fatigue life calculation method for spur gear is proposed,and the effect of shot peening on the spur gear contact fatigue life is investigated.It is found that peening treatment can enhance absolutely the gear contact fatigue life.