ABSTRACT

During fabrication of deck house block in passenger ships, the problem of unexpected large deformation and distortion frequently occurs. Hence, amending of these deformation become more important in thin plate welding. The spot heating and line heating methods were very widely employed to amend deformation of thin plate structures. Few papers are available on the working conditions of spot heating method but only little information on deformation control. In this study, evaluation was carried out on the temperature distribution of spot and line heating methods using FEA and practical experiments for various heating time. In FEA, heat input model was established using Tsuji's double Gaussian heat input mode (Tsuji, I., 1988). This model was verified by comparing with experimental data. Also radial shrinkage and angular distortion due to spot heating were determined and compared with experimental results. Thermo elasto-plastic analysis was performed using commercial FE code, MSC/MARC. Radial shrinkage and angular distortion were measured using 3D measuring apparatus. Based on these results, criteria for amending thin plate fairing was established in our fabrication yard.

INTRODUCTION

In recent years of ship building technology, thin plate welding and control of its deformation is considered as a serious problem. During the fabrication of thin plate structures, welding distortions are inevitable and serious problem of whole ship structure in strength. Because of the need to reduce total weight of ships, deck plate thickness has been gradually reduced resulting in use of 5mm thickness plate associated with buckling distortion during deck block fabrication. The best way to control buckling distortion is to optimize welding parameters and structural parameters. But this requires lot of trial and error experiments. In many cases, line heating or triangular heating is not in much correct to control thin plate deformation.

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