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US 4,067,240 AGranted
Process of shot peening and cleaning and preparing shot pellets therefor
OwnerJohn C. Straubinventor
Life of this patent
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OwnerJohn C. Straubinventor
Estimating the term…
A process of compression stressing shot pellets to increase the fatigue strength or resistance thereof to brittle fractures by impact of the pellets during shot peening and cleaning operations wherein the elastic radial tensile stress at the surface of the pellets is maintained at a safe low value during initial compression stressing and preparation for and performance of peening and cleaning operations. The process entails subjecting the pellets initially to compression stresses of sufficiently low value to avoid the spontaneous formation of superficial or surface cracks in pellets formed of notch sensitive material and then subjecting the pellets to stresses normal in shot peening and cleaning operations. The compression stresses occurring at the surface of the pellets in the initial step of the process minimize the likelihood of formation of surface cracks in the pellets when subsequently subjected to the greater impact forces to which the pellets are subject during peening and cleaning operations, thus increasing the life of the pellets.
In a process of compression stressing shot pellets for use in shot peening and cleaning operations, the step of imparting residual compressive stresses to substantially the entire surface of each pellet before use thereof in a peening or cleaning operation, said stresses being imparted to said pellets by impact of a value less than that to which the pellets are subjected in peening and cleaning operations and so related to the hardness and notch sensitivity of the metal of the pellets as to stress the surfaces of the pellets without creating cracks in the surfaces of the pellets and to produce a distribution of residual stresses in the pellets favorable to increase of fatigue strength thereof.
The method of increasing the fatigue life of metal shot pellets which comprises compression substantially the entire surfaces of said pellets at a low intensity in a first step and thereafter further compression stressing the surfaces of said pellets in a second step at an intensity substantially greater than the intensity of said initial stressing thereof, said first step compression stressing being of an intensity to prevent the formation of cracks in the pellets during the first step and during higher intensity compression stressing in the second step.
Dependencies are inferred from the claim text.