Simulation And Experimental Study Of Supersonic Shot Peening Gas-solid Two-phase Flow

Surface strengthening technology can form a deep residual compressive stress layer on the metal surface without changing the metal material,and greatly improve the strength,fatigue resistance and corrosion resistance of parts.The commonly used conventional shot peening technology has a large diameter of 0.5?1.5mm,but a small injection speed of 20 ? 60 m/s;However,the supersonic particle bombardment technology has a high pellet injection speed of 340 ?1200m/s,but the pellet diameter is very small,ranging from 1 ? 50 ? m;Therefore,combining the advantages of the two technologies and improving them,this paper puts forward a supersonic shot peening strengthening method,which accelerates the pellets with supersonic airflow,the diameter of the pellets is larger than that of supersonic particles,and the injection speed is larger than that of conventional shot peening.In this paper,the flow field of gas-solid two-phase flow and the three-dimensional residual stress field in the process of supersonic shot peening are studied by a combination of fluid dynamics simulation,finite element simulation and experimental testing.The main research results obtained are as follows:First,the ANSYS FLUENT fluid dynamics software was used to establish a 3D gas-solid two-phase flow model for 2 Ma supersonic shot peening.The standard k-?model was used to introduce the turbulent flow,the DPM discrete model was used to simulate the pellet acceleration,and the Lagrangian method was used.The pellets were tracked,and then the flow process of the supersonic airflow and the acceleration process of the pellets were simulated.On this basis,in order to determine the best entrance position of the pellets,the influence of the entrance position and the diameter of the pellets on the velocity field of the pellets was studied;at the same time,the supersonic shot peening was determined according to the outer flow field of the pellets.Best spray distance.Secondly,taking E690 offshore steel as the research object,the single shot model of supersonic shot peening was established by ABAQUS finite element software,and the plastic deformation of target at high strain rate was considered by Johnson-Cook constitutive model.The effects of shot speed,shot diameter,shot kinetic energy and momentum on surface residual compressive stress,maximum residual compressive stress and residual compressive stress layer depth were studied.The result show that when that pellet diameter is constant,there is a pellet velocity with better shot peen effect,and when the pellet velocity is constant,there is also a pellet diameter with better shot peening effect.Then,in order to study the influence mechanism of kinetic energy and momentum of pellets on shot peening effect,the shot peening effect with the same kinetic energy or momentum of pellets but different diameters and velocities of pellets was studied,that is,the comparative simulation study of "high-speed small pellets" and "low-speed large pellets".The results show that the effect of "high-speed small pellets" is better,which also verifies the correctness of the direction of supersonic shot peening proposed in this paper.On the basis of single shot model,a stochastic multi-shot model of supersonic shot peening which is more in line with actual shot peening process is established by using Python PIL library.On this basis,the influence of shot peening coverage on residual stress field and target surface roughness is studied.It is found that coverage has little influence on maximum residual compressive stress.With the increase of coverage,the residual compressive stress on the surface and the surface roughness of the target first increase and then decrease.Therefore,considering the strengthening effect and shot peening efficiency,100% coverage is the most suitable for supersonic shot peening.The supersonic shot peening test was carried out on E690 offshore steel samples by pneumatic shot peening machine,and the residual stress of E690 steel was detected by X-ray diffraction residual stress analyzer.Through comparative analysis,it was found that the simulation results were basically consistent with the test results,which verified the correctness of the simulation model and results.This research has certain theoretical guiding value for the development of supersonic shot peening technology.