14th International Conference on Shot Peening

Repeatability of residual stress from shot peening assessed using hole-drilling

Michael R., George C. Kaschner, and Adrian T. De Wald

Hill Engineering, LLC, Rancho Cordova, CA USA

mrhill@hill-engineering.com

Abstract

Residual stress is a key outcome from shot peening and measured residual stress versus depth profile data are an expected element of quality control. Despite this expectation, there is a lack of published work that establishes the repeatability of the residual stress versus depth profile near shot peened surfaces. The present work is therefore directed to document methods useful for assessing residual stress repeatability and describing results of initial work. An initial step establishes the intra-laboratory (within a single laboratory) repeatability of near surface residual stress profile measurements for a variety of measurement techniques. The data from this initial step show that the slotting and hole-drilling techniques have precision suitable for further study, and precision better than the x-ray diffraction technique. Further work applies the hole-drilling technique to assessing the repeatability of residual stress from shot peening in workpieces typical of aerospace production. A first group of measurements enables the assessment of residual stress repeatability at multiple locations on large single parts. A second group of measurements enables the assessment of residual stress repeatability at a single location on multiple parts. A third group of measurements enables assessment of residual stress repeatability over time, where the same part is processed to the same specification in the same facility. Overall, the data indicate that the residual stress versus depth profile provided by shot peening is highly repeatable, with repeatability standard deviation being a small fraction of the peak levels of near surface compression. Subsequent efforts are directed to similar assessments for other surface treatment processes and in a range of industrial contexts.