Sample interview questions: Describe the principles behind laser-induced acoustic imaging and its applications in structural health monitoring.
Sample answer:
Laser-induced acoustic imaging is a powerful technique that combines laser technology with acoustic sensing to non-destructively evaluate the structural health of materials. The principle behind this method lies in the generation and detection of ultrasound waves using lasers.
This technique typically involves illuminating a sample with a pulsed laser beam. The laser pulse generates a thermoelastic effect on the sample’s surface, causing rapid heating and subsequent expansion. This expansion leads to the generation of ultrasonic waves, known as laser-generated ultrasound (LGU), due to the sudden release of energy in the form of a localized pressure wave. The LGU propagates through the material and interacts with its internal features, such as defects or boundaries between different materials.
To detect these ultrasonic waves, a sensitive sensor, such as a piezoelectric transducer, is used. The transducer converts the acoustic waves into electrical signals that can be processed and analyzed. By scanning the laser beam over the surface of the material and correlating the time-of-flight and amplitude of the detected ultrasonic waves, it is possible to construct an image of the internal structure of the material.
Laser-induced acoustic imaging has found numerous applications in the field of structural health monitoring (SHM). One prominent application is the detection and characterization of defects in materials, such as cracks or delaminations. The high spatial resolution and sensitivity of this technique enable the identification of small defects that may not be easily detectable using traditional inspection methods. This makes it particularly use… Read full answer