Specimen edge effects on bending fatigue of carburized steel

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The effects of specimen geometry on the fatigue behavior of SAE 4320 steel carburized at 927 °C were evaluated with two sets of cantilever bend specimens, one set machined with square edges and one set machined with round edges. The specimens with square edges exhibited a 13% lower fatigue limit. In comparison to the rounded samples, the lower fatigue limit in the square-edged samples was attributed to the presence of a higher volume fraction of retained austenite in the sample corners and a lower surface residual compressive stress. As a result of the differences in residual stress, preferential crack initiation sites existed in the square-edged samples at a location approximately 200 to 900 ώm from the square edge. The implications of this study on laboratory analyses of the bending fatigue performance of carburized gear steels are discussed.

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Cohen, R.E., Matlock, D.K. & Krauss, G. Specimen edge effects on bending fatigue of carburized steel. JMEP 1, 695–703 (1992).

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  • Fatigue
  • Austenite
  • Residual Stress
  • Fatigue Crack
  • Specimen Geometry