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Weld Distortion Control Methods and Applications of Weld Modeling
F. W. Brust Paul Scott ABSTRACT
A virtual fabrication technology (VFT) modeling procedure is introduced in this paper. It is a state-of-theart fabrication modeling tool which can handle all aspects offabrication including forming, cutting, machining, and welding. This simulation tool was developed by Battelle and Caterpillar over the past ten years. It can model extremely large and complicated structural fabrications. Extensive full-scale experiments have validated the accuracy and predictive power. It can be used to reduce fabrication cost and improve quality by minimizing and controllingdistortions. Several application examples are presented to illustrate how to apply this tool in welded structure design and manufacture.
Many researchers have tried to develop modeling methodologies to simulate the welding process, but the modeling techniques that have been developed have often been too complex, less accurate, or too labor intensive to be applied industrially. Althoughsignificant progress has been made in the finite-element modeling of welding processes in resent years, many of the modeling techniques are still far short of being used successfully for the control of residual stress and distortion in actual structures. Since 1996, Battelle and Caterpillar have been working together to develop an industrial-use methodology and user-friendly software forpredicting weld residual stress and distortion in large and complicated structures. Brust et al (1981, 1998, 2003), Dong and Brust (2000) and Yang et al (2000a-b, 2002a-c) performed residual stress analyses for actual large structures. A large amount of manpower and equipment was invested for model development, program coding, and validation. Finally, a Virtual Fabrication Technology (VFT) and a weldmodeling computer tool was developed and is now used routinely in the Caterpillar design process worldwide. VFT is a state-of-the-art fabrication simulation technology that allows rapid solutions for large, complex metallic structures containing both single-pass and multi-pass welds and allows the user to consider or input all critical variables. It can be used in product design stages to help the welddesign and in the manufacture stage to determine the optimal weld processes to minimize welding-induced distortion.
VIRTUAL FABRICATION TECHNOLOGY MODEL
The procedure of simulating the arc welding processes with the VFT is discussed in Brust et al (1998, 2000, and 2005). Three kinds of modeling procedures: local weld residual stress analysis procedure, moving-arc analysis procedure, andlump-pass analysis procedure are included in the software. Local weld residual analysis procedure has been widely used in predicting and mitigating weld residual stress in the pressure vessels (Brust, 2005, and references sited therein) and nuclear piping systems. The moving-arc analysis procedure was developed for predicting distortion in large and complicated welded structures.
Transactions,SMiRT 19, Toronto, August 2007 Transactions, SMiRT 19, Toronto, August 2007 .
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DISTORTION CONTROL TECHNIQUES AND ADVANTAGES
Two tremendous advantages are obtained by developing fabrication solutions via the computer. First, designing the fabrication to minimize or control distortions can significantly reduce fabrication costs. Second, controlling thefabrication-induced residual stress state can significantly enhance the structure's service life. For distortion control, fabrication design via modeling can: • • • • • eliminate the need for expensive distortion corrections reduce machining requirements minimize capital equipment costs improve quality permit pre-machining concepts to be used
Residual stress control via modeling can: • • • • • Reduce...