Analytical Considerations for Residual Stress Best Practices and Case Studies
A-10 ASIP Hill AFB United States
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The fatigue life benefits of engineered residual stress processes such as cold expansion of fastener holes and laser shock peening are well known and have been demonstrated by test in countless applications over the past few decades. Typical USAF methodologies do not directly account for the effects of residual stress and consequently often do not accurately replicate the fatigue life improvement from these processes. This, and the lack of in-situ process validation, have contributed to the USAF hesitation to take advantage of these benefits in damage tolerance analyses. Recently, AFRL and the A-10 and T-38 Aircraft Structural Integrity Program ASIP offices have engaged in a concerted effort to move to a physics based analytical approach to account for engineered residual stress in Damage Tolerance Assessments DTAs.To support this initiative, a specific task under the A-10 ASIP Modernization VI TLPS program, PWS 3.6.4 Crack Growth Analyses in Residual Stress Fields, was established with Northrop Grumman and Hill Engineering LLC to continue development of a fundamental analytical framework for incorporation of engineered residual stress. One key aspect of this initiative is to provide best practices, lessons learned, and case studies to the larger community. This best practices and case studies document is specifically developed to meet this initiative. This initial release establishes a framework, with the opportunity to add additional information and case studies from the community as methods mature and develop.