The main objective of this study was to assess the effects of a machine-like scratch on the fatigue life of a high strength steel. The steel chosen for this study was 4340 steel heat treated to an ultimate strength of 210 ksi. To accomplish this, constant amplitude fatigue tests were conducted on unnotched specimens with and without a 0.002 inch deep machining scratch which was machined across the specimens surface. Specimens with scratches that had been shot peened were also tested to see if the compressive residual stresses from the shot peening would provide any relief from the stress concentration caused by a scratch. The specimen was shot peened after the scratch was machined on the specimens surface. Tests results showed about a 40 percent reduction in the materials endurance limit due to the machine-like scratch. However, the tests on the specimens that were shot peened after a scratch was machined into the specimens surface, showed that the shot peening almost eliminated the effects of the stress concentration caused by a scratch. In this study it was also shown that a small-crack fracture mechanics analysis can predict the total fatigue life of constant amplitude fatigue tests with and without machine-like scratches.


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    Title :

    On the effects of a machining-like scratch on the fatigue life of 4340 steel


    Contributors:


    Publication date :

    1999


    Size :

    12 Seiten, 18 Quellen


    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English






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