• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2004.10a
• /
• pp.263-268
• /
• 2004

In the present study, a Nd;YAG Laser (pulse type) was used to emit ultrasonic signals to a test material. In addition, a total ultrasonic investigation system was designed by adopting a Fabry-Perot interferometer, which receives ultrasonic signals without any contact. For non-destructive test SM45C, which contains some flaws was used as a test material. Because it is easy to align light beam in receiver, and the length of the light beam does not change much even if convex mirror leans towards one side, confocal Fabry-Perot interferometer, which has stable frequency, and PI control are used to correct interfered and unstable signals from temperature, fluctuation and time shift of laser frequency. Stable signals are always obtained by the feedback of PI circuit signals in the confocal Fabry-Perot interferometer. The type, size and position of flaws inside the test material were examined by achieving the stabilization of an interferometer. This study presented a useful method, which could quantitatively investigate the fault of objects by using a Fabry-Perot interferometer.

• Proceedings of the Optical Society of Korea Conference
• /
• 2005.02a
• /
• pp.112-113
• /
• 2005

• Journal of the Korean Society for Nondestructive Testing
• /
• v.33 no.2
• /
• pp.160-164
• /
• 2013

A laser ultrasonic inspection system is a non-contact inspection device which generates and measures ultrasonics by using laser beam. A laser ultrasonic inspection system provides a high measurement resolution because the ultrasonic signal generated by a pulse laser beam has a wide-band spectrum and the ultrasonic signal is measured from a small focused spot of a measuring laser beam. In this study, galvanic corrosion phenomenon was measured by non-destructive and non-contact method using the laser. The case of mixed foreign material on the part of corrosion was assumed and laser ultrasonic experiment was conducted. Ultrasonic was generated by pulse laser from the back side of the specimen and ultrasonic signal was acquired from the same location of the front side using continuous wave laser and Confocal Fabry-Perot Interferometer(CFPI). The characteristic of the ultrasonic signal of exist foreign material part was analyzed and the location and size of foreign material was measured.

• Journal of the Optical Society of Korea
• /
• v.17 no.4
• /
• pp.323-327
• /
• 2013

A laser ultrasonic inspection system has the advantage of nondestructive testing. It is a non-contact mode using a laser interferometer to measure the vertical displacement of the surface of a material caused by the propagation of ultrasonic signals with the remote ultrasonic generated by laser. After raising the ultrasonic signal with a broadband frequency range using a pulsed laser beam, the laser beam is focused to a small point to measure the ultrasonic signal because it provides an excellent measurement resolution. In this paper, foreign materials are measured by a non-destructive and non-contact method using the laser ultrasonic inspection system. Mixed foreign material on the corroded part is assumed and the laser ultrasonic experiment is conducted. An ultrasonic wave is generated by pulse laser from the back of the specimen and an ultrasonic signal is acquired from the same location of the front side using continuous wave laser and Confocal Fabry-Perot Interferometer (CFPI). The characteristic of the ultrasonic signal of existing foreign material is analyzed and the location and size of foreign material is measured.