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Proceedings Paper

Nature defect evaluation of laser welded thin plate using laser guide wave
Author(s): Kyung Seok Song; Jae Yeol Kim
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Paper Abstract

The longitudinal, shear and surface waves have been used to an Ultrasonic wave exploration method to identify internal defects but it has technical difficulties to detect defects in a limited space with having several millimeters board thickness. It is applicable to use Lamb wave, a kind of induction ultrasonic wave that has a relatively high inspection efficiency and defect detection sensitiveness compare to perpendicular or square explorations in terms of the internal defect detection in these kinds of thin board. The Lamb wave is a special type of induction ultrasonic wave to propagate to a board and it is effective to inspect such as board structure, cell structure, etc. Recently a laser is being used to generate Lamb wave but it not being widely utilized because of difficulties in receiving and selective generation in various modes Lamb wave generating and a low S/N ratio, wide range of generating frequency band when a laser is used. This paper aims to study that the defect exploration method to specimen's thickness, using an characteristic of an ultrasonic wave generating in ablation area and thermoelasticity area, has been applied to using a way of receiving it by Air-Coupled Transducer and transmitting it by an ultrasonic wave and a way of non-contact receiving and transmitting ultrasonic wave using a laser. The longitudinal, shear waves have been used in 60mm thickness specimen and Lamb wave in 3mm to run artificial defect detection test. In this way, the usefulness of non-contact laser ultrasonic wave has been verified. To confirm the possibility of implementation on natural defect existing at real welding part, thickness in 3mm SM45C and STS304 artificial defect specimen has been made and defect detection test using Lamb wave has been executed. Detected signal by signal treatment has been expressed in visual not RF signal. By doing so the convenience of defect detection has been attempted and the effectiveness of defect signal visualization using Lamb wave has been confirmed compare with defect image through SAT.

Paper Details

Date Published: 1 November 2007
PDF: 8 pages
Proc. SPIE 6423, International Conference on Smart Materials and Nanotechnology in Engineering, 64232V (1 November 2007); doi: 10.1117/12.779893
Show Author Affiliations
Kyung Seok Song, Chosun Univ. (South Korea)
Jae Yeol Kim, Chosun Univ. (South Korea)

Published in SPIE Proceedings Vol. 6423:
International Conference on Smart Materials and Nanotechnology in Engineering
Shanyi Du; Jinsong Leng; Anand K. Asundi, Editor(s)

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