The powerful shot peening technology of gear machining

Practice has proved that powerful shot peening technology is to improve the gear tooth bending fatigue strength and contact fatigue strength of the important method, is to improve the gear anti-seizure ability, the important way to improve the service life of gear. Powerful shot peening technology first developed in the 1920 s, mainly used in military field. The scope of application of promotion, as a powerful shot peening process to enhance the capacity of gear fatigue strength and life has been confirmed by many enterprises. The working principle of powerful shot peening process is mainly by using high speed jet small steel shot hit by spraying the workpiece surface at room temperature, make the workpiece surface material produces elastic-plastic deformation and render the higher residual compressive stress, thereby improving workpiece surface strength and fatigue strength. Shot peening surface elastic deformation occurs, on the one hand, make parts at the same time also produced a large number of twin and dislocation, make the material surface machining aggrandizement. Shot peening effect on surface morphology and properties of mainly displayed in the change of parts surface hardness, surface roughness, stress corrosion resistance and fatigue life of parts. Parts of material surface layer under the impact of the steel shot beam of cyclic plastic deformation occurred. Depending on the nature of the material and state, the following changes will take place after shot peening material surface, the hardness changes, the change of organization structure, phase transition, the formation of surface residual stress field and the change of surface roughness, etc. Measurement method of shot peening intensity when a piece of metal to accept steel shot flow spray strike when bending. Saturation and shot peening intensity are two important concepts of shot peening process. Saturation is refers to under the same conditions continue to spraying without changing state of the mechanical properties of the region by spray. The so-called shot peening intensity, is through striking prefabricated into certain specifications of the sheet metal ( The specimen) , within the prescribed time to achieve the strength of the saturation degree, specimens and bend the arc of high value to measure the degree of the strength of the spraying. At present, the most widely used of the shot peening in the standard of motor vehicle engineering institute by arman's shot peening test - — Arc height method, the method by the GM company J. O. Almen（ Almen) Put forward, and by SAEJ442a and SAE443 standard measurement method, the point is to use a certain specifications of the spring steel specimens by detecting shot peening after the shape of the changes to reflect the effect of shot peening. Single shot peening was carried out on the thin plate specimens, because of the surface layer under the action of the projectile in tensile deformation caused, so bending to the angled shot peening spherical plate. Usually in a span distance measuring spherical arc height value, using it to measure the strength of the shot peening. The arc height value is by putting the almen test plate is fixed on the special fixture, after shot peening specimens removed again, then use almen specimens gauge measurement by single shot peening produced under the action of variables involved in drawing shape ( The arc height value) 。 If use specimens measured arc high value is 0. 35 mm, as 0. 35A。 Shot peening intensity of another kind of testing method for residual stress testing, that after a powerful shot peening artifacts for the detection of residual stress, concrete testing method for X-ray diffraction method. In American SAEJ784a standard recommend the following methods: X-ray of the incident and diffraction beam must be parallel to the gear tooth root, cylindrical spur gear and cylinder