Welding induced distortion in large structures is a major quality concern in industry. Many methods have been proposed in recent years to minimize the welding induced distortion. Among the available methods, transient thermal tensioning has been shown effective for minimizing the welding induced buckling distortion for T-joints. Due to the complexity of the welding process, different structures may require different strategies for distortion control. This paper presents a finite element simulation study on the distortion control for large box beam structures. The transient thermal tensioning method is applied through differential preheat on the two side plates of the beam. The effects of the preheating parameters including the average preheating temperature, temperature differential, and the preheating location are analyzed. It has been found that differential preheating control is effective in adjust the welding induced twist distortions. However, excessive differential preheating could generate bowing distortions. To determine an optimal preheating strategy, the distortions in all the three dimensions of a beam need to be considered simultaneously.
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