Nakahata K, Karakawa K, Ogi K, Mizukami K, Ohira K, Maruyama M, Wada S, Namita T, Shiina T
Graduate School of Science and Engineering, Ehime University, 3 Bunkyo, Matsuyama, Ehime 790-8577, Japan.
Graduate School of Science and Engineering, Ehime University, 3 Bunkyo, Matsuyama, Ehime 790-8577, Japan.
Ultrasonics. 2019 Sep;98:82-87. doi: 10.1016/j.ultras.2019.05.006. Epub 2019 Jun 10.
A pulsed laser illuminates a target zone that causes rapid thermoelastic expansion, generating broadband high-frequency ultrasonic wave (photoacoustic wave, PA wave). We developed a PA microscopy (PAM) with a confocal area of laser and ultrasonic wave for applications in nondestructive testing (NDT). The synthetic aperture focusing technique (SAFT) is applied in the PAM for the three-dimensional (3D) imaging of interior flaws. Here, we report proof-of-concept experiments for the NDT of a subsurface flaw in a thin laminar material. Graphical abstract (a) shows a specimen of carbon-fiber-reinforced plastic (CFRP) with an artificial delamination. Here, it should be noted that the group velocity varies directionally due to the strong anisotropy of the CFRP specimen (see Graphical abstract (b)). By considering the group velocity distribution in the SAFT, the shape and location of the subsurface delamination were accurately estimated as shown in Graphical abstract (c). Coating the surface of the CFRP specimen with a light-absorbent material improved the amplitude of the PA wave. This finding showed that the signal-to-noise ratio of the waves scattered from the flaws can be improved.
脉冲激光照射目标区域，引发快速热弹性膨胀，产生宽带高频超声波（光声波，PA波）。我们开发了一种激光与超声波共焦区域的光声显微镜（PAM），用于无损检测（NDT）。合成孔径聚焦技术（SAFT）应用于PAM中，用于内部缺陷的三维（3D）成像。在此，我们报告了对薄片状材料中表面下缺陷进行无损检测的概念验证实验。图形摘要（a）展示了带有人工分层的碳纤维增强塑料（CFRP）试样。在此应注意，由于CFRP试样的强各向异性，群速度会随方向变化（见图摘要（b））。通过在SAFT中考虑群速度分布，如图形摘要（c）所示，准确估计了表面下分层的形状和位置。用吸光材料涂覆CFRP试样表面可提高PA波的幅度。这一发现表明，从缺陷散射的波的信噪比可以得到改善。
