Papers by Author: Young June Kang

Abstract: The ESPI (Electronic Speckle Pattern Interferometry) is a real-time, full-field, non-destructive optical measurement technique. In this study, ESPI was proposed for the purpose of vibration analysis for new and composite materials. Composite materials have various complicated characteristics according to the materials, orientations, stacking sequences of the ply and boundary conditions. Therefore, it was difficult to analyze composite materials. For efficient use of composite materials in engineering applications the dynamic behavior (i.e., natural frequencies and nodal patterns) should be informed. With the use of Time-Average ESPI, one could analyze vibration characteristics of composite material by real time easily. We manufactured two kinds of laminated composites (i.e., symmetry and asymmetry) which were consisted of CFRP (Carbon Fiber Reinforced Plastics) and the shape of the test piece was of rectangular form.

Abstract: A laser-based ultrasonic inspection system is a non-contact scanning device with a high spatial resolution and a wide spectrum bandwidth. In this paper, we developed a laser-based ultrasonic inspection system by fabricating a pulse laser and a Confocal Fabry-Perot Interferometer (CFPI) with a dynamic stabilizer. The dynamic stabilizer generates ultrasound by adaptively obtaining the time of the maximum gain of the CFPI whose gain is varied with the time. Then, a computer adaptively corrects the measurement error by using the gain of the CFPI at the measuring time. In this paper, we describe the hardware configurations and the control algorithms to build the stable laser-based ultrasonic inspection system. We have investigated an ultrasonic signal in the time and frequency domain to detect micro cracks through experiments. We experimentally confirmed that the proposed error correction method is effective for improving the performance of the system and the configured ultrasonic inspection system is stable