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US 4,034,585 AGranted
Process of compression stressing metals to increase the fatigue strength thereof
OwnerJohn C. Straubinventor
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OwnerJohn C. Straubinventor
Estimating the term…
A process of compression stressing metals to increase the fatigue strength or resistance to brittle fractures thereof by shot peening or surface rolling wherein the elastic radial tensile stress of the metal is maintained at a safe low value at the time when subsurface yield incident to initial compression stressing occurs. Initial processing entails compression stressing of the metal under conditions imparting compression stresses of sufficiently low value to avoid the formation of superficial or surface cracks in notch-sensitive metals followed, where required, by final processing wherein the metal is subjected to compression stressing under conditions imparting compression stresses of sufficiently high value to produce a favorable distribution of residual compression stress and residual tensile stress for increase of the fatigue strength of the metal.
A process of compression stressing a metal work piece by shot peening or surface rolling thereof to increase the fatigue strength thereof consisting of the step of compression stressing substantially the entire selected surface of the work piece by imparting compression stresses of a value so related to the thickness, the hardness and the notch sensitivity of the work piece as to avoid the formation of surface cracks during the peening or rolling operation and produce a distribution of residual stresses in the work piece favorable to increase of fatigue strength, and a second step of compression stressing said work piece following the first step by imparting substantially uniformly to the selected surface of the initially stressed work piece compression stresses of greater magnitude to produce a greater depth of residual compressive stress in the work piece.
The method of increasing the fatigue life of a metal part which comprises compression stressing the surface of a metal part at a low intensity in a first step and thereafter further compression stressing the surface of said part 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 metal part during the first step and during higher intensity compression stressing in the second step.
Dependencies are inferred from the claim text.