Analysis of Residual Stresses Resulting from Cold Rolling of Notches and Their Effect on Fatigue Behavior.
Research and development rept.,
DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER ANNAPOLIS MD SHIP MATERIALS ENGINEERING DEPT
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The effects of cold forming on the fatigue behavior of threads were analyzed using slip-line field and finite-element analyses. Bolt threads were simulated using notched rotating cantilever-beam fatigue specimens of Inconel 718. The slip-line fields for wedge indentations, with some modifications, were used to analyze the deformation process of notch rolling. Stresses on the deepest slip lines were used in an elastic finite-element analysis of the internal stresses existing outside the slip-line field during deformation. Negatives of the loads on the notch surface from the indentor were used in a second elastic finite-element analysis to determine the internal stresses resulting from unloading. These two stress analyses, with a correction for yielding, were employed to map the residual stress distribution around the rolled notch. The predicted residual stress distribution showed an intense compressive region below the notch root. However, a short distance away from and to the side of the notch, there began a region of residual tensile stresses. This stress distribution was then used to rationalize the fatigue crack propagation behavior of Inconel 718 rotating cantilever-beam fatigue specimens with rolled and machined notches.
- Metallurgy and Metallography
- Fabrication Metallurgy