Successful Round Robin Analyses Resulting from the Engineered Residual Stress Implementation Working Group

Abstract The application of engineered residual stresses (ERSs) on aircraft structure provides an opportunity to significantly extend the total fatigue life of critical components. In order to reach required service life goals within budgetary constraints, the ability to implement ERS into analyses is essential. However, it has been repeatedly demonstrated that in order to properly quantify, apply, and analyze ERSs, sophisticated analytical tools, advanced technical knowledge, and specialized training are required. The ERS implementation (ERSI) working group provides the opportunity for collaborative development of best practices for government, contractors, and engineers supporting the implementation of ERSs into life predictions. The ultimate goal of the working group is to develop a more holistic framework for the implementation of ERS, with validated tools and processes for application to aircraft structures, minimizing expensive test programs, and offering benefits to all stakeholders. The ERSI Fatigue Crack Growth Analysis Method committee has taken the initiative to develop round robin fatigue life predictions for cold expanded holes. An initial round robin effort was completed to quantify the epistemic uncertainties in the prediction of fatigue crack growth, given a fixed set of input data. The results of this round robin are presented, including the variations in the predictions and comparison with test results, as well as lessons learned and best practices.