Laser‐Ultrasonic Measurements of Residual Stresses in a 7075‐T651 Aluminum Sample Surface‐Treated with Low Plasticity Burnishing

Low‐plasticity burnishing (LPB) is used to introduce deep compressive surface residual stresses that improve the durability of parts. A non‐destructive measurement of residual stresses, their anisotropy, and distribution as a function of depth is being sought to verify initial process quality and residual stress retention over time. Laser‐ultrasonic measurements of Rayleigh wave and surface skimming longitudinal wave (SSLW) velocities were used together to evaluate the magnitudes and directions of the two principal stresses independently of LPB‐induced texture variations. The results agree with x‐ray measurements at the surface. In addition, it was found that the laser‐ultrasonic pulse generation mechanism was surface‐process dependent.

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