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RESEARCH PAPERS

Noncontact Ultrasonic Sensing for Seam Tracking in Arc Welding Processes

[+] Author and Article Information
S. B. Zhang, Y. M. Zhang

Welding R&D Laboratory, Center for Robotics and Manufacturing Systems, University of Kentucky, Lexington, KY 40506

R. Kovacevic

Southern Methodist University, Dallas, TX

J. Manuf. Sci. Eng 120(3), 600-608 (Aug 01, 1998) (9 pages) doi:10.1115/1.2830164 History: Received January 01, 1997; Revised July 01, 1997; Online January 17, 2008

Abstract

A novel seam tracking technology based on high frequency ultrasound is developed in order to achieve high accuracy in weld seam identification. The transmission efficiency of the ultrasound is critical for obtaining a sufficient echo amplitude. Since the transmission efficiency is determined by the difference in impedance between the piezoelectric ceramic and air, match layers are designed to optimize the transmission efficiency by matching impedance. Since the air impedance depends on the density and velocity of the ultrasound, which both depend on the temperature, the optimization has been done for a wide bandwidth. Also, the receiving circuit is designed so that its resonance frequency matches the frequency of the ultrasound. As a result, the sensitivity of the noncontact ultrasonic sensor is improved 80-fold. By properly designing the focal length of the transducer, a high resolution ultrasound beam, 0.5 mm in diameter, is achieved. Based on the proposed sensing technology, a noncontact seam tracking system has been developed. Applications of the developed system in gas tungsten arc welding (GTAW) and CO2 gas metal arc welding (GMAW) processes show that a tracking accuracy of 0.5 mm is guaranteed despite the arc light, spatter, high temperature, joint configuration, small gap, etc.

Copyright © 1998 by The American Society of Mechanical Engineers
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