The objective of the present paper is to develop nonlinear finite element method models for predicting the weld-induced initial deflection and residual stress of plating in steel stiffened-plate structures. For this purpose, three-dimensional thermo-elastic-plastic finite element method computations are performed with varying plate thickness and weld bead length (leg length) in welded plate panels, the latter being associated with weld heat input. The finite element models are verified by a comparison with experimental database which was obtained by the authors in separate studies with full scale measurements. It is concluded that the nonlinear finite element method models developed in the present paper are very accurate in terms of predicting the weld-induced initial imperfections of steel stiffened plate structures. Details of the numerical computations together with test database are documented.
The aim of this paper is to derive an empirical formulation for predicting welding-induced biaxial compressive residual stresses in welded steel plate panels. A test database for full-scale models of welded steel plate structures is developed. Elastic-plastic finite element method solutions, associated with thermal stresses in welded steel plate panels, are also developed. The proposed formula is derived by a curve fitting of the databases obtained from both full-scale measurements and numerical computations as a function of plate thickness and weld leg length. The paper demonstrates an applied example of the derived formulations to prevent the thermal buckling of thin steel plate panels that occurs during the welding process.
Due to of high intensity, lower noise and easy controllability of the heat, induction heating system became well known. Induction heating method has been suggested as substitute for the gas heat source and adopted in the automation of curved hull forming system.In this study, an investigation was accomplished to find the effects on the change of material properties when the induction heating was applied on the mild steel plate. Plates were heated using weaving method to get sufficiently heat affected zone and then cooled with water or in the air. The mechanical properties of the heated plate were evaluated. As results, the tensile test, impact test and microstructures satisfied the class rule.
In this paper, a localization method is proposed for improving the curved plate fabrication process. In the curved plate forming, checking the similarity of a manufactured plate to a CAD model is a critical step, which can be done by aligning the manufactured plate to the CAD model. Although there exist several localization methods, they may not be suitable for the curved plate forming since they do not consider production efficiency (the shortest cutting length for trimming margin) for the subsequent assembly process. Therefore, in this work, a constraint for minimizing the cutting length is introduced in the localization scheme and an algorithm is proposed to handle the problem. A manufactured plate is measured and a constraint is imposed on the reference points of a CAD model and the measured points to limit the direction of the movement of the measured points in the solution process. Through this algorithm, the CAD model and the measured points are aligned such that the shortest cutting length is obtained. After the alignment, the cutting lines are computed for marking on the manufactured plate. Various curved plates taken from the real ship manufacturing process are used to demonstrate the performance of the proposed algorithm.
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