| Shot peening is one of the important measures to improve the performance of metalmaterial. Liquid jet cavitation peening was used to improve the performance of metalmaterial by producing plastic deformation and residual stress on the material surface,in these processes, high speed and pressure liquid jet produce air bubbles whenimpacts to the material surface, these bubbles produced high temperature and highimpact pressure when blasted on the material surface. In recent years, comapare withtraditional shot peening, liquid jet peening has following advantages, such as goodstrengthening effect, low cost, easy to carry out, green environmental protection andeasy to achieve automation, so extensive research has been developed.In this paper, cavitation water (emulsion) jet technology was taken as thefoundation, in order to achieve efficient, green shot peening and improve productperformance of metal. Theoretical analysis, numerical simulation, experimentao studyand finite element simulation method were used to study the birth, development andcollapse process of cavitation jet. ANSYS-FLUENT software was used to simulateflow field under different inlet pressure under diagonal nozzle cavitation in submergecondition and then the cavitation jet experiment was built. Water (Emulsion)-jetcavitation peening was carried out on45steel, brass, Q235A steel and316stainlesssteel under best test parameters to study the performance changes of these materials.ANSYSY/LS-DYNA software was applied to build model to simulate residual stressinduced by water-jet cavitation peening. Water-jet cavitation peening strengtheningeffect was verified through the simulated result contrast with residual stress measuredin X-ray experiments and this provided a theoretical reference for liquid jet cavitationpeening application.Based on theoretical analysis and research of others, the characteristics of flow fieldto present the optimal structure angle cavitation nozzle of shrinkage angle13.5°,diffusion angle30°,diameter1mm, was simulated and analyzed, using theANSYS-FLUENT software, using RNGκ-εturbulence model. The results showed thatto the angle cavitation nozzle of the structure, as the outlet pressure does not changed,the different inlet pressure was one of the important factors affecting cavitationintensity, along with the increase of the inlet pressure, the cavitation phenomenon andcontinuously was enhanced, but the enhancement of cavitation phenomenon isdecreased after10MPa. And the result was validated by means of experimental systemunder different pressure external flow field in a high speed camera. 45steel, brass, Q235A and316stainless steel were strengthed by fluid jetcavitation peening, the performances, macro and micro structure were analyzed beforeand after strengthening. The influence of jet cavitation on the surface properties ofmaterials was analyzed, and the best reinforcement parameters correspondingwas found.Water-jet cavitation peening was carried out to strengthen45steel. The best testparameters were determined by45steel surface performance changes, the surfacestrengthening effect was obviously and there was a certain thickness hardened layerafter water-jet cavitation peening on45steel’s surface. Jet time and jet pressure hasmarked influence on the ability of water-jet cavitation peening. The surface qualityintroduced by water-jet cavitation peening is higher than that introduced by traditionalshot peening and this improved the surface properties of45steel.The submerged water-jet cavitation peening was employed to strengthen brasssurface. The significant surface strengthening effect of water-jet cavitation peening onbrass was observed and the hardened layer of the brass spceimen had certain thickness.Friction coefficient and wear quantity reduced in friction and wear test process whenstrengthened by water-jet cavitation peening and this improved the abrasion resistanceof brass.Configurated emulsion has good rust prevention effect on Q235A steel.Emulsion-jet cavitation peeing was carried out on Q235A steel and then three pointbending fatigue test was carried out on hardened material. The fatigue life of Q235Asteel was significantly improved when Q235A steel was strengthened by emulsion-jetcavitation peening.Water-jet cavitation peening was carried out on316stainless steel, there were noobvious macroscopic plastic deformation on the surface of samples and there were alot of dispersed pits and significant plastic deformation on the impact zone. Theresidual stress test showed that the impact region produced a large residual stress onimpact zone of316stainless steel.ANSYS/LS-DYNA software was applied to establish residual stress model basedon the water-jet cavitation peening experiments. Completely damping settings wasmore come to real and effective reflect the propagation of stress wave and variationrule of equivalent stress. The value of residual stess and the thickness of residualstress layer along the Z axis were increased when the number of shock wave increased.The value and distribution of residual stress through numerical simulation aggred well with the X-ray experimental results and this showed that using ANSYS/LS-DYNAsimulation software can be effiviently simulated residual stress distribution inducedby water-jet cavitation peening. |
PDF Full Text Request