Simultaneous measurement of thickness and ultrasonic wave velocity using a combination of laser-generated multiple wave modes in the thermoelastic regime

ABSTRACT

This paper introduces a reliable laser ultrasonic technique without damage to the surface in the thermoelastic regime that provides a one-side access method for simultaneously determining the thickness and ultrasonic wave velocity by employing multiple wave modes. Initially, this study determines the optimal separated distance between two laser beams to achieve an effective signal-to-noise ratio of the employed wave modes. Subsequently, a pre-established ratio of 0.95 for the velocity of skimming longitudinal waves and longitudinal waves enables the simultaneous calculation using a combination of the skimming longitudinal wave, reflected shear wave, and mode-converted longitudinal wave in a single measurement. Experiments were carried out on various plane plates made of aluminium alloy 6061, ranging in thickness from 4 to 20 mm, demonstrating a high accuracy in thickness measurement, with a maximum absolute error of 0.05 mm. Compare the results of ultrasonic wave velocity measurements with theoretical calculations, the maximum absolute error is 32 m/s and 80 m/s for longitudinal wave and shear wave, respectively.

KEYWORDS:

• Laser ultrasonic
• thickness
• ultrasonic velocity
• thermoelastic regime
• multiple wave mode
• simultaneous measurement

Acknowledgments

The authors are grateful for the financial support provided by the Ministry of Education, Science, Sports, and Culture of the Government of Japan (MEXT)

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.