Study On Ultrasonic Shot Peening With Pneumatic Aid

The main failure modes of mechanical parts are fracture, surface damage and excessive plastic deformation. Fracture failure has the biggest damage on parts and mechanical equipment, causing larger personnel and equipment accidents, fatigue fracture is the main form of parts fracture failure, so improving the ability to resist fatigue failure can be significantly enhance the reliability of mechanical parts and service life. The shot peening technology is an effective method to improve the fatigue strength of metal parts and has a wide range of promotion and application in industrial and agricultural production.The harmful residual tensile stress and micro-cracks on part surface can be eliminated by shot peening process, and part surface fatigue strength and corrosion resistance can be also improved. After shot peening treatment, part surface residual compressive stress layer can effectively prevent formation of surface fatigue cracks and extension to the internal. Moreover shot peening process also has the advantages of simple operation, low cost, and wide adaptability.Ultrasonic shot peening is a new surface modification technology. It uses ultrasonic wave as power source, smaller apparatus, less energy, and the peened surface compressive stress layer depth and the maximum residual stress values are superior to conventional shot peening process, the workpiece surface roughness was significantly decreased.But existing ultrasonic shot peening equipments have the shortcomings of inflexible processing methods and difficult removal of waste timely, so as to influence application range and peening processing effect. In view of above shortcomings of Ultrasonic shot peening process, this paper presents the pneumatic auxiliary ultrasonic shot peening methods, it is mainly combine ultrasonic shot peening system with pneumatic auxiliary transport system to improve the working manner of the original shot peening equipment, and then to realize shot’s recycling and the high efficiency shot peening strengthening for complex work-piece. The main research content includes:1. Base on in-depth study on the principle and ultrasonic shot peening equipment composition, the working principle of pneumatic auxiliary ultrasonic peening and their components are proposed; the experiment device combining with the functional properties and structural characteristics of the component units are designed; and the feasibility and scientific of the new type of shot peening program are verified.2.After analysis of the principles and characteristics of the ejector, the projectile ejector suitable for the test requirements is designed and manufactured according to the the pneumatic auxiliary transport system requirements, the cycle of projectile transmission is realized. Through researching on the ultrasonic horn design principles and construction features, a new ultrasonic horn with large amplitudes ratio is designed by combining with the experimental requirements and optimal design method, using ANSYS finite element software to optimize a single half-wave horn. The results show that the optimized horn has not only a large amplitude magnification ratio but also a good shape factor, so as to meet the demands of experiment basic requirements.3. This paper clears of various parameters effect on peening through choosing different process parameters to do the pneumatic ultrasonic shot peening strengthening experiment, using the pressure test system to measure the maximum impact of the pellets under different conditions, comparing and analyzing experimental results. 4.The process of residual stress generation and development is analyzed by using the LS-DYNA finite element software to simulate single pellets impact process. Simulation results show that:experimental results of the pellet impact force equates with simulation results; simulation results of the residual stress along the vertical direction in the contact region are similar to the theoretical calculation results, so the simulation results can be applied to carry out preliminary forecast and analysis to ultrasonic shot peening.