Papers by Keyword: Scanning Acoustic Microscopy (SAM)

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Authors: Noh Yu Kim, Hwan Seon Nah, Sang Soon Lee
Abstract: In order to evaluate the degradation of the epoxy coating in nuclear power plants, acoustic wave velocities of epoxy films are measured using defocused scanning acoustic microscopy system(SAM). Unlike metals, the surface of the epoxy coating on the concrete liner is so thin and wavy that the conventional ultrasonic techniques for acoustic velocity of epoxy coating are hard to apply. Acoustic velocities of bulk waves are determined from V(z,t) curves of mode-converted waves generated in the film by SAM. Epoxy films are fabricated and degraded under various accelerated aging conditions, and both of longitudinal and shear wave velocities of the epoxy film are measured. Approximately 10% of reduction in acoustic wave velocity is observed from experimental results when the aging is developed fully in epoxy films. It is also found that longitudinal wave is more sensitive to deterioration of epoxy coating than transverse wave.
Authors: Job Ha, Kyung Young Jhang
Abstract: The detection of interfacial micro-delamination in the thin-layered structure such as the electronic package becomes very important as the electronic device becomes smaller and thinner. The conventional method used to detect the delamination in an electronic package is to use a scanning acoustic microscope (SAM). However, despite its high performance qualities, SAM is often faced with a tricky decision when a delaminated gap is too small. In this paper, a novel method based on ultrasonic nonlinearity is proposed to overcome this limit. The proposed method is integrated into the conventional SAM equipment, and its effectiveness is verified by experiments for the Newton Ring and the real semiconductor package that have micro-delaminations. The results showed that the nonlinear parameter had good correlation with the gap size of delamination. A method of imaging the nonlinear parameter is also proposed to assure the feasibility of the proposed method in the field application.
Authors: Noh Yu Kim, Cheol Kyou Lee
Abstract: Scanning acoustic microscopy (SAM) has been applied successfully to measure leaky surface wave(LSAW) velocity from V(z) curve for material characterization. Besides LSAW, SAM produces a variety of wave modes in the material propagating with different phase speeds and features, one of which is the mode-converted ultrasound. In this paper, a novel method for simultaneous measurement of longitudinal and transverse acoustic wave velocities using the mode-converted ultrasound is developed and studied at SAM. Each ultrasound arriving at the acoustic lens with different speed and phase (or time-of-flight (TOF)) is measured by the defocused transducer to calculate longitudinal and transverse wave velocities. Simple mathematical ray analysis for the mode conversion is conducted to determine the relationship of acoustic velocities with TOF of the waves in plate. Experimental results for metals and glass show that the longitudinal and transverse wave velocities measured by the proposed method are as accurate as maximum 3% in error.
Authors: C.S. Kim, Dong Su Cho, Ik Keun Park
Abstract: We attempted to estimate the residual stress which evolved during the shot peening of Al 7075 alloy using leaky surface acoustic wave (LSAW). Shot peening was conducted to produce a variation in the compressive residual stress with the depth from the surface at a shot velocity of 30m/s. The LSAW velocity was measured using a scanning acoustic microscopy (SAM). The Vickers hardness profile obtained inwards from the surface showed significant work hardening of the near surface layer with a thickness of about 0.3mm. The variation in the LSAW velocity through the shot peened surface layer was in good agreement with the distribution of the residual stress measured by X-ray diffraction.
Authors: Noh Yu Kim, Hee Joon Kim, Se Woong Oh, N. Hozumi, Cheol Kyou Lee, Min Sung Hong
Abstract: In this paper, elastic moduli of nanostructured alumina are evaluated by simultaneous measurement of longitudinal and shear wave velocities using mode-converted ultrasound in scanning acoustic microscope (SAM). Mode-converted longitudinal and shear waves inside alumina sample are captured to calculate acoustic wave velocities and determine elastic constants such as Young’s modulus and Bulk modulus. Al2O3 nanostructured alumina samples are formed by compacting micro-sized Al2O3 powder with nano-sized Al2O3 powder from 10wt% to 50wt%, and tested by SAM to investigate elastic moduli. A correlation is found from experiment that the more percentage of nano-particles are added, the higher elastic moduli are obtained. It is also shown that the mode-converted ultrasound is sensitive enough to characterize mechanical modulus of nanostructured alumina quantitatively.
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