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Applications Using Laser Ultrasonics

Developments of the Fundamental Techniques for Remote Ultrasonic Inspections
Detection techniques for remote ultrasonic inspections have been studied. A pulsed detection laser with a high power of 1kW was developed to probe targets at a distance. The laser was combined with the interferometer which was specially designed to reduce the noise attributed to the fluctuation of the laser power. Simulated subsurface defects on aluminum samples were fairly detected at a distance over 1 m.
Drill hole image detected at a distance of 1m
Precise Measurements of Sound Velocities of Solids at High Temperatures
Ultrasonic waves are generated and detected in a non-contact manner using a laser based system. The system offers the precise measurements of sound velocities at high temperatures over 1000 degree C. To overcome the poor sensitivity to diffused surfaces, a novel phase conjugate method was developed. Several samples including single crystals were measured up to 1200 degree C.
Temperature dependence of longitudinal velocity for a WSi2 single crylstal
Sound Velocity Measurements of Thin Films at High Temperatures
To evaluate elastic moduli of thin films, sound velocities are measured using GHz ultrasonic pulses. Sound velocity is calculated from the film thickness and the period of echoes. Sound velocities of a diamond film of 25 micrometer thickness are measured at RT and 600 degree C. Ceramics films are also examined.
Detected longitudinal pulses for the diamond film at RT and 600 degree C
Calibration of Acoustic Emission (AE) Sensors in a wide frequency range
A broad band calibration method for AE sensors was developed. A laser ultrasonic pulse was adopted as a standard AE source. Magnitude and phase characteristics of sensors were determined in the frequency range from several tens of kHz to several MHz with this method.
Numerical Analysis of Ultrasonic field
For the purpose of grasping the image of ultrasonic field, numerical computation is being carried out on a model of isotropic medium. Acoustic impedance density on the axis of the circular transducer is being computed and investigated.

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