Noncontact NDE of microscopic surface-breaking cracks using laser generated and detected ultrasonic surface waves

Adam Cooney; James L. Blackshire

doi:10.1117/12.538928

20 July 2004 Noncontact NDE of microscopic surface-breaking cracks using laser generated and detected ultrasonic surface waves

Adam Cooney, James L. Blackshire

Author Affiliations +

Proceedings Volume 5393, Nondestructive Evaluation and Health Monitoring of Aerospace Materials and Composites III; (2004) https://doi.org/10.1117/12.538928
Event: NDE for Health Monitoring and Diagnostics, 2004, San Diego, CA, United States

Abstract

Laser ultrasonic imaging of surface acoustic waves on a material surface provides a non-contact and sensitive method for detecting and characterizing defects and anomalies in aerospace and industrial materials. It has recently been shown that the surface acoustic wave interactions with sharp material discontinuities such as surface-breaking cracks provides an additional benefit of an intensification of the displacement field in the immediate vicinity of the crack site. This near-field intensification can be exploited by scanning, point-by-point, a laser-ultrasonic system to create detailed microscopic images of the surface breaking cracks. In this effort, a number of laser ultrasonic system parameters were studied to better understand the optimized conditions to imaging surface breaking cracks using ultrasonic generation in the thermoelastic regime, and laser detection of ultrasound fields using heterodyne interferometer. In particular, laser beam sizes, separation distances, and motives were varied. In addition, several different time-gating analysis methods were studied, which had a significant effect on both the characteristics as well as the quality of the resultant crack images.

Citation Download Citation

Adam Cooney and James L. Blackshire "Noncontact NDE of microscopic surface-breaking cracks using laser generated and detected ultrasonic surface waves", Proc. SPIE 5393, Nondestructive Evaluation and Health Monitoring of Aerospace Materials and Composites III, (20 July 2004); https://doi.org/10.1117/12.538928

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