Ultrasonic inspection system for detecting small flaws at far surface of steel plate

摘要

This paper presents the development of inspection system using ultrasonic for steel plate manufacturing. Generally, internal defects in the final product of steel plate are inspected manually by human operators, which is a time consuming process. In this research, the crystal of an ultrasonic probe at natural frequency suitable for steel plate examination was developed. In our design, high sensitivity (i.e. high signal peak amplitude) and good resolution were achieved using a (water coupling) probe structure, without ceramic wear plate, and a signal processing called the 1-bit technique. Backing material of the probe was carefully designed and experimented to obtain proper impedance matching with the probe's crystal by varying its material composition. Jig with a dual-probe support to speed up the inspection of a steel plate was implemented. Moreover, the 1-bit technique was applied to improve resolution of the inspection and to detect small flaws close to the far surface of the steel plate. The developed probe has more sensitivity than that of commercial probes in terms of frequency response. The 1-bit processing technique has been realized and simulated and it showed advantages over the conventional method for processing time and accuracy.