Measurement of Absolute Acoustic Nonlinearity Parameter Using Laser-Ultrasonic Detection

For our next entry in the library, we are looking at a more research-oriented paper, made by the team of Dr. Seong-Hyun Park from the School of Mechanical Engineering at Hanyang University. The paper describes the use of a powerful non-destructive evaluation method called the nonlinear ultrasonic technique (NUT), combined with laser-ultrasonics. The NUT is known for its effectiveness in detecting microstructural changes in materials, such as thermal aging, fatigue damage, and creep at an early stage. It is able to examine the grain boundaries, second-phase precipitates, inclusions, and dislocation density, which is not possible with the conventional linear ultrasonic technique using ultrasonic velocity and attenuation. It works by measuring the nonlinear behavior of ultrasonic waves as they pass through a material. The most widely method used to measure this nonlinear behavior is with a piezoelectric detection method, which requires good mechanical contact with the material and can be difficult to calibrate.

This study by Dr. Seong-Hyun Park team’s proposes a new, non-destructive method using a laser-ultrasonic detection system, based on a laser-interferometer with a photorefractive crystal, to measure the nonlinear behavior of ultrasonic waves in the material. The method is validated by measuring the nonlinearity parameter β value for samples of copper and Al6061-T6. The results of this study indicate that the proposed laser-ultrasonic detection method is a promising tool for non-destructive evaluation (NDE) of industrial components as it is non-contact, and therefore does not require a couplant, and has the ability to inspect different materials without complex calibration.

Link to paper