Application of Peening Surface Residual Stresses for Durability and Damage Tolerance Improvements in Wing Attachment Lugs

Engineered residual stresses have long been utilized to enhance the fatigue properties of metallic components.  The Boeing Company has conducted an investigation  to establish a calculable life benefit of engineered residual stresses for applications to titanium structural components.  Both glass bead peening and laser shock peening were selected for this investigation.  Recent work has focused on both optimizing laser shock peening for complex titanium hardware as well as performing sub-component testing to define the fatigue improvements available from both peening methods.
      A scale-up method based on the ASIP building block approach was used in the laser shock peening optimization work.  Residual stresses were measured on small test blocks, representative geometry blocks, sub-component test articles, and full-scale test articles.  The criteria for selection, residual stress data, as well as the chosen laser shock peening parameters will be discussed.  Both laser shock peening as well as glass bead peening were applied to sub-component test articles and cycled through a typical wing up-bending flight spectrum.  Durability and damage tolerance benefits from both laser shock and glass bead peening have been calculated and will be discussed.