Assessment and Validation of Cosα Method for Residual Stress Measurement

Author:  Nate Peterson, Yuji Kobayashi, Bill Traeger, Paul Sanders
Source:  ICSP-13
Doc ID:  2017045
Year of Publication:  2017
Abstract: For proper control of shot peening surface treatments, measurement of residual stresses in the treated material is an important consideration. Traditionally, X-ray diffraction techniques have allowed for non-destructive testing of the material for qualification purposes by utilizing traditional stationary diffractometers. Recently, portable residuals stress analyzers have seen increased interest due to the ease of use. The cosα technique has shown promise as a faster method of measuring residual stresses in portable devices due to its ability to measure an entire Debye ring at once from the two-dimensional detector, thus not requiring multiple sample tilts. In this study, shot-peened and in-situ loaded steel samples were subjected to residual stress measurement from both the cosα and sin2 technique using a portable device and laboratory diffractometer respectively. Two types of data analyses were performed to calculate the residual stresses based on linear- regression and least-squares analysis. The results from this work show the equivalency in both accuracy and precision of the cosα to the traditional sin2 technique in measuring residual stresses in shot-peened materials. Based on these results, recommendations are presented on the use of x-ray diffraction for residual stress measurement.

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