• Applied Microscopy
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• v.50
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• pp.25.1-25.11
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• 2020

Scanning acoustic microscopy (SAM) or Acoustic Micro Imaging (AMI) is a powerful, non-destructive technique that can detect hidden defects in elastic and biological samples as well as non-transparent hard materials. By monitoring the internal features of a sample in three-dimensional integration, this technique can efficiently find physical defects such as cracks, voids, and delamination with high sensitivity. In recent years, advanced techniques such as ultrasound impedance microscopy, ultrasound speed microscopy, and scanning acoustic gigahertz microscopy have been developed for applications in industries and in the medical field to provide additional information on the internal stress, viscoelastic, and anisotropic, or nonlinear properties. X-ray, magnetic resonance, and infrared techniques are the other competitive and widely used methods. However, they have their own advantages and limitations owing to their inherent properties such as different light sources and sensors. This paper provides an overview of the principle of SAM and presents a few results to demonstrate the applications of modern acoustic imaging technology. A variety of inspection modes, such as vertical, horizontal, and diagonal cross-sections have been presented by employing the focus pathway and image reconstruction algorithm. Images have been reconstructed from the reflected echoes resulting from the change in the acoustic impedance at the interface of the material layers or defects. The results described in this paper indicate that the novel acoustic technology can expand the scope of SAM as a versatile diagnostic tool requiring less time and having a high efficiency.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.6
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• pp.534-549
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• 2009

As the thin film technology has emerged in various fields, adhesion of the film interface becomes an important issue in terms of the longevity and durability of thin film devices. Diverse nondestructive methods utilizing acoustic techniques have been developed to assess the interfacial integrity. As an effective technique based on the ultrasonic wave focusing and the surface acoustic wave(SAW) generation, scanning acoustic microscopy(SAM) has been investigated for adhesion evaluation. Visualization of film microstructures and quantification of adhesion weakness levels by SAW dispersion are the recent achievements of SAM. To overcome the limitations in the theoretical dispersion model only suitable for perfectly elastic and isotropic materials, a new model has been more recently developed in consideration of film anisotropy and viscoelasticity and applied to the adhesion evaluation of polymeric films fabricated on semiconductive wafers.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.5
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• pp.437-443
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• 2010

In recent years, as nano scale structured thin film technology has emerged in various fields such as the materials, biomedical and acoustic sciences, the quantitative nondestructive adhesion evaluation of thin film interfaces using ultra high frequency scanning acoustic microscopy(SAM) has become an important issue in terms of the longevity and durability of thin film devices. In this study, an effective technique for investigating the interfaces of nano scale structured thin film systems is described, based on the focusing of ultrasonic waves, the generation of leaky surface acoustic waves(LSAWs), V(z) curve simulation and ultra high frequency acoustical imaging_ Computer simulations of the V(z) curve were performed to estimate the sensitivity of detection of micro flaws(i.e., delamination) in a thin film system. Finally, experiments were conducted to confirm that a SAM system operating at a frequency of 1 GHz can be useful to visualize the micro flaws in nano structured thin film systems.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.4
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• pp.118-125
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• 1991

Acoustic microscopy has attracted much interest recently as potential nondestructive evaluation technique for detecting and sizing defects of surface and sub-surface. Also acoustic emission testing method has been developed for detecting microcracks which is more than 30${\mu}m$ in length quantitatively on ceramics. In the present paper, acoustic emission during the four point bending test in hot-pressed sintered $Si_3N_4$ specimen which was stressed by thermal shock, has been measured by high sensitive sensing system. The surface and sub-surface cracks were detected by scanning acoustic micrscope of 800 MHz and conventional ultrasonic testing in C-scope image. The purpose was to investigate the location and size of cracks by SAM and AE technique, whose experimental data demonstrate good for detecting microcracks.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.5
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• pp.291-296
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• 2006

The residual stress in shot-peened Al 7075 alloy was evaluated using surface acoustic wave (SAW). Shot peening was conducted to produce a variation in the residual stress with the depth below the surface under a shot velocity of 30 m/s. The SAW velocity was measured from the V(z) curve using a scanning acoustic microscopy (SAM). The Vickers hardness profile from the surface showed a significant work hardening near the surface layer with a thickness of about 0.25 mm. As the residual stress became more compressive, the SAW velocity increased, whereas as the residual stress became more tensile, the SAW velocity decreased. The variation in the SAW velocity through the shot peened surface layer was in good agreement with the distribution of the residual stress measured by X-ray diffraction technique.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.4
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• pp.418-430
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• 2012

The present paper reviews the micro and nano nondestructive evaluation(NDE) technique that is possible to investigate the surface and measure the acoustic properties. The technical theory, features and applications of the ultrasonic atomic force microscopy(UAFM) and scanning acoustic microscopy(SAM) are illustrated. Especially, these technologies are possible to evaluate the mechanical properties in micro/nano structure and surface through the measurement of acoustic properties in addition to the observation of surface and subsurface. Consequently, it is thought that technique developments and applications of these micro/nano NDE in advanced industrial parts together with present nondestructive industry are widely possible hereafter.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.04a
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• pp.127-133
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• 1991

Acoustic microscopy has attracted much intrest recently as potential mondestructive evalution technique for detecting and sizing defects of surface and sub-surface. Also acoustic emission testing method has been developed for detecting microcracks which is more than 30 umm in length quintitatively on ceramics material. In the present paper, acoustic emission during the four point bending test in hot-pressed sintered Si$\_$3/N$\_$4/ specimen which was stressed bythermal shock has been measured by high sensitive sensing system. The surface and sub-surface cracks were detected by scanning acoustic microscope of 800 MHz and conventional ultrasonic testing in C-scope image. The purpose was to investigate the location and size of cracks by SAM and AE technique, whose experimental datas demontrates good agreement for detecting microcracks.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.321-323
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• 2004

전자 제품에 사용되는 부품 ㆍ소재의 신뢰성 품질 평가를 위해 정밀한 모터의 제어기술, 첨단신호처리 기술, 압전소자 기술의 발달로 미세변화 계측의 재현성, 고분해능, 표면과 내부의 이미지관찰, 또한 미소부위에서 재료의 누설탄성표면파의 음속측정이 가능한 초음파현미경에 대한 연구가 최근 들어 활발히 진행되고 있다. (중략)

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.426-430
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• 2003

본 연구에서는 초음파현미경의 기하학적 원리와 초음파현미경의 특징중 하나인 V(z)곡선의 간섭파형을 시뮬레이션 하였고, 실제 초음파현미경의 V(z)곡선법을 이용하여 미소영역에서의 누설탄성표면파 음속을 측정하였다. 초음파현미경을 이용한 V(z)곡선법의 음속측정결과가 시뮬레이션 음속값과 큰차이를 보이지 않으므로 미소영역에 초음파현미경의 V(z)곡선법을 적용하여 초음파의 음속측정이 가능함을 확인하였다. 이는 향후 초음파현미경을 이용하여 미세한 재료의 물성평가에 적용할 수 있을 것으로 기대된다.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.3
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• pp.261-268
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• 2001

An investigation on nondestructive evaluation of thermal stress-nduced damage in the composite laminates (3mm in thickness and $[+45_6/-45_6]_s$ lay-up angles) has been performed using the thermo-acoustic emission technique. Reduction of thermo-AE events due to repetitive thermal load cycles showed a Kaiser effect. An analysis of the thermo-AE behavior determined the stress free temperature of composite laminates. Fiber fracture and matrix cracks were observed using the optical microscopy, scanning electron microscopy and ultrasonic C-sean. Short-Time Fourier Transform of thermo-AE signals offered the time-frequency characteristics which might classily the thermo-AE as three different types to estimate the damage processes of the composites.