Near-Surface Residual Stress Measurements for Aerospace Structures

ABSTRACT: It is widely recognized that near surface residual stresses play a significant role in fatigue performance. Tensile residual stresses are of concern because they accelerate fatigue crack initiation and fatigue crack growth relative to what would occur in the absence of residual stress. Compressive residual stresses, on the other hand, have the opposite effect and can be used to improve fatigue performance. To effectively understand and predict residual stress effects on fatigue durability or crack initiation, which accounts for the majority of the total component life under high-cycle applications, accurate and reliable residual stress data are required in the near-surface region. The proposed work plan will develop improvements to a novel near-surface residual stress measurement technique and will demonstrate the effectiveness of this measurement technique under representative conditions. Phase I evaluation will include an assessment of measurement repeatability and accuracy. The measurement technique will also be validated during Phase I using independent measurement technologies. BENEFIT: The proposed residual stress measurement technique development is a significant improvement to existing residual stress measurement technology that would fill a critical gap in capability for near-surface residual stress measurement, enabling high-quality measurements in the near-surface regime under conditions typical of the aerospace industry. This technology is important to many industries as methods advance for assessment of fatigue performance in the presence of residual stress.