Tsunaji Kitayama

Frequency dependence of images in scanning laser source technique for a plate

Defect imaging using scanning laser source technique has been investigated for a plate with rounded defects and notch-type defects in our previous studies. This paper examines frequency dependence of the defect images with both calculations and experiments in order to acquire clearer images. Both calculation and experimental results for a straight notch revealed that clearer images of notch-type defects can be obtained in the range of low frequency-thickness product below about 200 kHz mm. Moreover, images of the defects of various shapes were obtained by synthesizing images from eight receiving transducers, and similarly to the case of the straight notches, they became more clearly in the low frequency range.

Detection of Delamination in GFRP and CFRP by Microwaves with Focusing Mirror Sensor

A technique to detect delamination in composite materials by noncontact, rapid and high sensitive microwave reflectometry with a focusing mirror sensor was proposed. The focusing mirror sensor, which has high sensitivity and resolution, is expected to detect delamination sensitively. In this paper, the ability of microwave inspection to detect delamination in glass fiber reinforced plastic (GFRP) and carbon fiber reinforced plastic (CFRP) was verified. As the results, the existences of 100 μm thick delamination in 3 mm thick GFRP laminate and 2 mm thick CFRP laminate were detected.

DEFECT IMAGING TECHNIQUE USING A SCANNING LASER SOURCE

Considering the applications to in‐line testing of products, water‐free imaging technique is required. This study described defect imaging technique using a scanning laser source. Laser beam was emitted onto a surface of a plate, and then guided waves excited at the laser source were detected by ultrasonic transducers fixed on the plate surface. For a plate with rounded defects, amplitude distributions obtained by scanning the laser source corresponded to thickness distributions, but for plates with rectangular notches, unwanted artifacts were seen due to reflection, diffraction, and ultrasonic attenuation. Then, using multiple receiving transducers and synthesizing multiple images, distinct defect images were obtained for a flat plate and a curved plate with rectangular notches.

Moiré deflectometry under incoherent illumination: 3D profiler for specular surfaces

We present a novel method for measuring a curved specular surface profile, which is the moiré deflectometry under incoherent (white light) illumination. In our proposed system, moiré is produced by a superposition of two pairs of Ronchi gratings to obtain orthogonal components of a normal vector on a surface under test. The grating pair was moved along an axis perpendicular to the grating plane to modulate a spatial frequency of the moiré. The moiré is reflected by a specular object, then observed with a calibrated stereo camera. Normal vector distribution of the tested surface was measured by analysis of intensity oscillations captured by the stereo camera as a function of the position of the moved grating. A surface profile was reconstructed by an integration calculation. We successfully measured surface profiles of deeply curved mirrors with the curvature from -20 to 20 m-1 by our system. Moreover, part of a miniature vehicle body, which has a complex curved specular surface, was also measured. Additionally, we theoretically and experimentally studied a measurable angle variation of the normal vector on the tested surface by our measurement system. We found that our system can allow to measure the angle deviation of 0.05 deg of the normal vector. This method has no ambiguity of slope and height measurements which is appeared in conventional deflectmetric metrologies. Furthermore, our proposed system only needs a single step calibration. Hence, the methodology we proposed has a potential to be developed into a 3D profiler for complex specular surfaces.