Behavior and Sustainability of Laser Shock Peening Induced Residual Stresses in Complex Fatigue Loading
Abstract
Laser Shock Peening (LSP) is a mechanical surface treatment that can improve the fatigue response of new and damaged metallic components by introducing beneficial compressive stresses into the near-surface regions. A major prerequisite for effective LSP is development of optimal residual stress fields that can be reliably sustained during fatigue loading. Although the effectiveness of surface treatment methods like LSP are widely acknowledged, relatively few structures and components use these methods to improve fatigue life. One particular reason is the uncertain behavior of treated engineering alloys under fatigue loading, especially with regards to the stability of the residual stresses. In alloys with strong texture and preferred crystallographic orientations, the same LSP processing parameters can produce different residual stresses and fatigue life improvement depending on where in the structure the peening is applied. The instability and redistribution of residual stresses during fatigue loading can strongly affect the crack propagation rates and overall fatigue life. Modeling techniques to predict residual stress generation during LSP and the subsequent fatigue crack propagation in alloys with isotropic material properties at all length scales are well established. Continuum mechanics based empirical and mathematical models work very well for estimation of the residual stress and fatigue performance of isotropic engineering materials. However, aerospace engineering alloys produced with different heat treatment methods have different microstructure properties and preferred orientation of the crystals (texture). The effectiveness of continuum mechanics based models on alloys with strong crystallographic preferred orientation is very limited. These models assume isotropic material properties which overlook the effect of crystal anisotropy that arises due to the texture of materials.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 11, 2017
- Source ID
- FA95501710325
Entities
People
- Muhammad Khan
Organizations
- Air Force Office of Scientific Research
- Coventry University
- United States Air Force