Professor of mechanical engineering, University of Manitoba, Winnipeg,
A new approach to decreasing the fatigue strength reduction factor of holes in ductile sheet metallic material is presented. The material is first stretched by dimpling centering about the region where the hole is to be made. Subsequent flattening of the material creates residual compressive stresses in the dimple region. The hole is then drilled leaving the peripheral material in a state of compressive stress.
Zero-to-tension fatigue tests on nominally 0.050-in. (1.27-mm) thick 2024-T3 alclad aluminum alloy specimens show a 36 percent decrease in the fatigue strength reduction factor by dimpling for 106 cycles to failure.
Paper ID: JTE10124J