Junichi Ishii

Synthetic aperture ultrasonic testing apparatus with shear and longitudinal wave modes

An ultrasonic synthetic aperture testing apparatus comprises transmitting/receiving sections having an ultrasonic wave probe for transmitting and receiving ultrasonic waves at multiple points on the surface of a steel material, an operation section for accumulating the received signals corresponding to the distance between the multiple points and a reproduction point in a desired region of the material under testing, and a display section for displaying an image formed as a result of this accumulation operation. The ultrasonic wave probe is provided with vibrators corresponding to the respective vibration modes so that two kinds of ultrasonic waves in different vibration modes may be transmitted and received. The accumulation section is provided with a mechanism which performs accumulation and arithmetic operation for the two kinds of waves in different modes.

Accurate Reconstruction of Flaws in Materials Using a Synthetic Aperture Ultrasonic Imaging System

A compact synthetic aperture ultrasonic imaging system, which rapidly reconstructs precise sectional images of flaws in steel, has been developed. Two side-drilled holes, 1 mm in diameter, at an interval of 1 mm were separately reconstructed when tested with a pulsed 5 MHz transmitted wave (wavelength:1.2 mm) and with a transducer whose aperture angle was 90°. Round profiles of larger diameter holes (4–8 mm) were also clearly reconstructed. Simulation studies have been carried out in order to predict the lateral and range resolutions of the imaging system. Most specifications of the imaging system have been determined by these simulation studies. Acquisitions of echo signals and calculations for synthetic aperture processing were carried out with a 16 bit microcomputer and the distance calculation between the transducer and reflectors were performed by a specially designed echo location calculator (5 microseconds per distance calculation). The transducer was scanned linearly along the tested blocks, and the received echoes were processed into a sectional image after each echo acquisition. It took 20 seconds to get a full image display. Another application to evaluate the crack size of the disk plates was also carried out. In this case, circular scanning was applied, and an error of ±0.5 mm in crack depth was obtained. From the viewpoint of fracture mechanics, a more accurate evaluation is required in nondestructive testing than that obtained by the conventional B-scan system. By using the developed system, the accuracy of flaw evaluation was improved.

High Resolution Ultrasonic Testing System Using Dynamic Focusing and Signal Correlation

Progress in fracture mechanics has made it necessary to evaluate flaw sizes exactly (within 1 or 2 wave lengths) in order to predict lifetimes of structural materials. To meet this requirement, the azimuthal resolution of ultrasonic testing must be improved, without increasing handling difficulty. Phased array(1), holography, and synthetic aperture are presently the best techniques available for improving the resolution(2). In addition, the signal processing array(3) has been studied as a method for acquiring ultrasonic beams of sharp directivity without enlarging the transducer size.

Automobile Weight Estimation Using a Neural Network for Automatic Transmission Control.

A neural network was applied to the estimation of vehicle weight for improved power-train control. The change in acceleration response according to vehicle weight was measured and utilized for the estimation. The measured acceleration response was input into the neural network which then output the estimated vehicle weight. The accuracy of the estimation was evaluated by computer simulation and field experiments. Using the throttle valve opening and the time signals of vehicle speed and acceleration, the weight estimation error was reduced to 20 kg, within an acceptable amount for the vehicle control.