Hidekazu Miyauchi

VISUALIZATION OF ULTRASONIC WAVES SCATTERED FROM REAR DEFECTS BY USING A LASER‐BASED IMAGING TECHNIQUE

We proposed a method for visualizing wave propagation in ultrasonic fields. This method generates thermal‐excitation ultrasonic waves on a specimen through pulsed laser scanning and detects the propagating signals via a reception transducer mounted on a fixed point. Dynamic images of ultrasonic waves propagated from a fixed point are created using the reciprocity principle of wave propagation. This method has the excellent feature that enables a visible and quick flaw inspection for actual objects. However, since this method visualizes all waves propagating on an object, it is disadvantageous in that defect echoes are often hidden in the forward traveling wave. In this research, we developed a data processing method for image enhancement of defect echoes. In the ultrasonic tests with aluminum plates or pipes with rear defects, we could visualize the defect echoes as they scatter in a radial manner, like water rings, on the surface of the specimen, which proved the validity of this data processing method. ...

Detection of wavefront using Hough transform from time-sequential images recorded by pulsed laser scan

The center location of the side hole (defect) in a solid material is roughly estimated using Hough transform. The measurement data recorded by a pulsed laser scanning system is used for the estimation. The incident and scattering wavefronts are characterized as the plane and conical tracks, respectively, using the stored data. The center location of the side hole is reasonably detected as the vertex coordinates of a conical track that is circularly scattered from the hole with the passage of time, after data preprocessing.

Extraction of Characteristic Lines from Visualized Images of Surface Transient Displacements for the Analysis of Ultrasonic Propagation

In this paper, a feature extraction method has been presented for the non-destructive detection of defects. This method is performed through the image analysis of visualized images, obtained from 2D scanning measurements of surface transient displacements, of ultrasonic wave propagation. The displacements induced by the ultrasonic wave on a 2D surface have been measured and visualized by scanning surfaces of opaque media using a laser system. The ultrasonic propagation was analyzed by extracting the characteristic lines by processing the visualized images. The scattering, diffraction and mode conversion of ultrasonic waves around artificial defects of various shapes are observed using the visualization method. The visualization system provides various kinds of visualized images, such as the propagation image, amplitude image, arrival time image, velocity image, and a series of successive images as an animation of the wave propagation. The proposed method is well suited to non-destructive inspection