Determination of residual stresses using laser-generated surface skimming longitudinal waves

Christophe Bescond; Jean-Pierre Monchalin; Daniel Levesque; Adam Gilbert; Richard Talbot; Makoto Ochiai

doi:10.1117/12.620374

19 May 2005 Determination of residual stresses using laser-generated surface skimming longitudinal waves

Christophe Bescond, Jean-Pierre Monchalin, Daniel Levesque, Adam Gilbert, Richard Talbot, Makoto Ochiai

Proceedings Volume 5767, Nondestructive Evaluation and Health Monitoring of Aerospace Materials, Composites, and Civil Infrastructure IV; (2005) https://doi.org/10.1117/12.620374
Event: Nondestructive Evaluation for Health Monitoring and Diagnostics, 2005, San Diego, CA, United States

Abstract

A laser-ultrasonic technique is described to non-destructively determine residual stresses in metals such as those produced by shot peening. The method is based on monitoring the small ultrasonic velocity change of the laser-generated surface skimming longitudinal wave (LSSLW) propagating just below the surface. The main advantage of using LSSLW is that the effect of surface roughness induced by shot peening is greatly reduced compared to using surface acoustic waves (SAW). To improve resolution in the measurement of small velocity changes, a cross-correlation technique is used with a reference signal taken on the same but unstressed material in similar conditions. Also, the low-frequency SAW can be used to correct the LSSLW results when affected by minute changes in the path length during the measurements. The validity of the approach is demonstrated by measuring quantitatively the near surface stress in a four-point bending experiment with different levels of surface roughness. Then, scanning results on properly and improperly laser shock peened samples are reported. In particular, the LSSLW velocity variations for the properly peened samples clearly show an increase in the laser-peened area well indicative of a compressive stress.

Citation Download Citation

Christophe Bescond, Jean-Pierre Monchalin, Daniel Levesque, Adam Gilbert, Richard Talbot, and Makoto Ochiai "Determination of residual stresses using laser-generated surface skimming longitudinal waves", Proc. SPIE 5767, Nondestructive Evaluation and Health Monitoring of Aerospace Materials, Composites, and Civil Infrastructure IV, (19 May 2005); https://doi.org/10.1117/12.620374

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