journal article

Journal Article

Text

Materials Transactions. 2018, 59(2), p. 320-323

Defect imaging from a remote distance by using scanning laser source technique with acoustic microphones

The Japan Institute of Metals and Materials

English

Text

2018-02-01

https://doi.org/10.2320/matertrans.M2017326

Atsuya Maeda, Takahiro Hayashi. Defect imaging from a remote distance by using scanning laser source technique with acoustic microphones. Materials Transactions, 2018, 59(2), pp. 320-323. https://doi.org/10.2320/matertrans.M2017326.

Images of defects in plate-like structures can be generated using the scanning laser source (SLS) technique. When a laser Doppler vibrometer (LDV) is used as a receiving device in the SLS technique, images of defects can be obtained through measurements conducted from a distance. Because an LDV cannot receive vibrations reffected from outdoor structures that may have rough surfaces and large fluctuations in a stable manner, this paper discusses an imaging technique using a SLS with acoustic microphones as a receiving device. The results of the experiments that were conducted using various distances between the test plate and microphone showed that the quality of the defect images gradually degraded because of the attenuation of sound in air as the distance increased. Moreover, when the laser beam was reffected back to the microphone after scattering over the plate surface, the laser beam directly generated signals in the microphone due to the photovoltaic effect or alternating heat, preventing the acquisition of defect images. Thereafter, in order to establish remote defect imaging, an acoustic transmitter was connected to the microphone unit. Most of the experimental equipment were located at a remote distance except for the small microphone unit and transmitter. The experimental system enabled the generation of images of the defect in the test plate located at distances of 4 and 6 m.

© 2017 The Japan Institute of Metals and Materials

84555

Defect imaging from a remote distance by using scanning laser source technique with acoustic microphones

The Japan Institute of Metals and Materials

English

2018-02-01

Materials Transactions

59

2

320

323

https://doi.org/10.2320/matertrans.M2017326

https://hdl.handle.net/11094/84555