SYMPOSIA PAPER Published: 01 January 1982
STP30096S

Evaluating the Effect of Residual Stresses on Notched Fatigue Resistance

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Many current fatigue design criteria for structural details present allowable stress ranges for specified design lives but neglect mean and residual stresses. The paper reviews published test results and shows that residual stresses and concomitant mean stresses can have a significant influence on fatigue resistance in certain cases. The beneficial effects of compressive residual stresses due to shot-peening are well-known. For example, shot-peening of non-load-carrying fillet-welded carbon steel and butt-welded constructional alloy steel has increased the fatigue strengths at two million cycles by 20 to 40 percent. Also, the fatigue resistance of weldments can be influenced significantly by the presence of residual stresses, provided the stress ratio is equal to or less than zero and the lives are greater than one million cycles. The fatigue strength of transverse butt welds with reinforcement intact at two million cycles has been increased by 12 percent and 24 to 33 percent for stress ratios of, respectively, 0 and −1 through thermal stress relief. Such improvement has also been shown for longitudinal non-load-carrying fillet welds (for example, attachments, gussets, etc.) where the increases in fatigue strength at two million cycles due to thermal stress relief for stress ratios of 0, −1, and −4 were, respectively, 15, 57, and 168 percent.

The paper presents an extension of the local-strain fatigue life initiation model to accommodate residual and mean stresses. The model is based upon the stress-strain function of Smith, Watson, and Topper and includes iterative solutions for Kσ and 2Nf. Changes in residual stresses due to cyclic loading and fatigue lives of notches at nonzero mean stresses are predicted and compared with experimental results. Also, further extensions of the model to accommodate plane strain—that is, thickness effects—and surface roughness are discussed.

Author Information

Reemsnyder, HS
Product Research, Research Department, Bethlehem Steel Corporation, Bethlehem, Pa.
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Developed by Committee: E08
Pages: 32–32
DOI: 10.1520/STP30096S
ISBN-EB: 978-0-8031-4841-3
ISBN-13: 978-0-8031-0711-3