| 摘要 |
PURPOSE: A method and a device for measuring the stress of a thin plate are provided to measure the stress applied on the thin plate without damages to a surface of a tested object by using lasers of low energy not generating ablation. CONSTITUTION: A method for measuring the stress of a thin plate comprises next steps. Pulse oscillation laser light source(21) for generating ultrasonic waves are projected on a tested object, thereby generating the ultrasonic waves on the tested object. Laser light source(31) for detecting ultrasonic waves having wavelengths different from pulse oscillation laser lights are projected to the tested object. Reflected lights of laser lights for detecting the ultrasonic waves receiving a Doppler shift by the vibration of the ultrasonic waves generated by projecting the pulse oscillation laser lights on the tested object are received and outputs lights of intensity depending on an amount of the Doppler shift. A strength waveform of the ultrasonic waves generated in the tested object is calculated by using the lights of the intensity depending on the amount of the Doppler shift. A frequency analysis of the strength waveform of the ultrasonic waves is performed so that two frequencies of plate ultrasonic waves of a S1 mode are calculated. The stress applied on the tested object is calculated by using a relation of the stress and two frequencies. [Reference numerals] (21) Pulse oscillation laser light source for generating ultrasonic waves; (31) Laser light source for detecting ultrasonic waves; (41) Receiving unit; (51a) Frequency spectrum calculating unit; (51b) Stress calculating unit; (51c) Correction line drawing unit; (61) Display unit |
