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RESEARCH PAPERS

Scanned Orbital Welding: Thermal Modeling and Lumped Adaptive Control

[+] Author and Article Information
H. Sfetsos, J. Angelis, C. Doumanidis

Department of Mechanical Engineering, Tufts University, Anderson Hall Room 221, Medford, MA 02155

J. Pressure Vessel Technol 121(4), 393-399 (Nov 01, 1999) (7 pages) doi:10.1115/1.2883721 History: Received May 04, 1999; Revised June 22, 1999; Online February 11, 2008

Abstract

Scan orbital welding of cylindrical vessel, flange, and piping parts is performed by their rapid revolution under a radially or axially translated heat source, with its power modulated so as to implement a specified thermal distribution. Thus, the plasma-arc welding torch sweeps the stainless steel surface to generate a desirable temperature field and the concomitant material features. A numerical simulation of the thermal field is developed for off-line analysis. On this basis, a lumped thermal regulator of the heat-affected zone, employing infrared temperature feedback at a single spot, as well as standard PI, gain scheduling, and self-tuning control algorithms is tested. The thermal model is also employed for real-time torch efficiency identification and compensation. The numerical reference model serves as the basis for an in-process adaptive thermal control system to regulate the temperature field, using thermal feedback from the infrared pyrometer. A distributed-parameter control strategy, with guidance of the torch motion and power by a new weighted attraction strategy to randomly sampled points, is tested on scan-welded flanges. The regulator is validated computationally and experimentally, and its applicability to other scanned processing of materials is considered.

Copyright © 1999 by The American Society of Mechanical Engineers
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