Investigation Of Abrasive Waterjet Peening On Surfaces With Different Geometrical Features

Abrasive waterjet peening?AWJP?is a surface modification technology by using the shot of abrasive waterjet to impact the surface of metallic components,causing the surface material to experience a plastic deformation below the recrystallization temperature,thus improving microstructure and inducing desired distribution of residual stress field?RSF?,and consequently improving the fatigue life of components.Unlike conventional shot peening?SP?,AWJP can achieve partial strengthening by using a single shot to impact target material,which provides the possibility of strengthening some complex and narrow surfaces such as root surfaces,shoulders and other complex geometrical surfaces with high stress concentration.Therefore,in this thesis,the influences of AWJP on target material with different geometrical features under different peening parameters such as shot velocity,shot radius and shot lapping rate are examined by mathematical calculation and simulation,and the results are as follows:?1?Mathematical models of predicting the residual stress distribution of target material with different geometrical features?i.e.,flat,spheres,pits,cylinders and grooves?after AWJP were established and verified by finite element model,respectively.Results show these mathematical models can accurately predict the residual stress of target material with different geometrical features after AWJP.?2?The finite element model of AWJP impact flat target material was established by using ABAQUS.And then the influences of peening parameters such as shot velocity,shot radius,and shot lapping rate on RSF and surface morphology were investigated.It is found that,as increasing the shot velocity,surface compressive residual stresss_scrs,maximum compressive residual stresss_mcrs and the depth of compressive residual stress z₀ all first increase and then remain unchanged,while the depth of maximum compressive residual stress z_m is almost unchanged.As increasing the shot radius,z_m and z₀ all increases,whiles_scrs ands_mcrs are almost unchanged.In additional,relatively uniform residual compressive stress layer can be obtained by setting reasonable shot lapping rate.Besides,increasing shot velocity and shot radius can induce larger pit,while increasing shot lapping rate can improve the surface morphology of target material.?3?The finite element models of using AWJP to impact target material with different geometrical features?spheres,pits,cylinders and grooves?were established by using ABAQUS,and then the influences of the curvature radius of spheres,pits,cylinders and grooves on RSF were also investigated.Results show thats_scrs?s_mcrscrs and z₀ all increase with an increase in the curvature radius,while z_m is almost unchanged,for using AWJP to impact the spheres and cylinders.However,s_scrs?s_mcrs and z₀ all decrease with an increase in the curvature radius,while z_m is almost unchanged,for using AWJP to impact the pits and grooves.?4?Under the same shot velocity,shot radius and curvature radius,the influence of different features on RSF was investigated,results show that the order ofs_scrs?s_mcrs?z_m and z₀ of induced RSF after AWJP from the biggest to the smallest is pits,grooves,flat,cylinders and spheres,for a single or multiple shot peening.For a relatively small radius of target with different features,RSF induced by AWJP has significantly different with that of flat target,while their results are almost same for a larger radius.