Welding deformation reduces the accuracy of ship hull blocks and decreases productivity due to the need for correction work. Preparing an error-minimizing guide at the design stage will lead to higher quality as well as higher productivity. Therefore, developing a precise method to predict the weld deformation is an essential part of it. This paper proposes an efficient method for predicting the weld deformation of complicated structures based on the inherent strain theory combined with the finite element method. The inherent strain is defined as the residual plastic strain after the welding heat cycle and is determined using the highest temperature and degree of restraint. In order to calculate precisely the inherent strain in real structures, it should be noted that the degree of restraint changes according to the different fabrication stages. The simulation of a stiffened panel confirmed the applicability of this method to simple ship hull blocks.

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The line heating process has long been used in plate forming of hull surfaces and it has depended on skillful workers. Since reduction of production cost is a major concern of shipbuilding companies, line heating work must be improved for higher productivity. In this paper, as a first step to automatic hull forming, a method is proposed to predict deformations due to line heating. It includes a simplified thermal elasto-plastic analysis to increase computing efficiency and to enable real-time visualization of deformed shapes. The simplified thermal elasto-plastic analysis method shortens the thermal elasto-plastic process and introduces inherent strains. Predicted deformations for line heated plates show good agreement with experimental results. For the prediction of deformation, a method to estimate heat flux of the torch is also introduced. The proposed method can be used in control and simulation of the line heating process with simplicity and efficiency.

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