• Journal of Welding and Joining
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• v.21 no.4
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• pp.31-38
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• 2003

Line heating is an effective and economical process for forming flat metal plates into three-dimensional shapes for plating of ships. Because the nature of the line heating process is a transient thermal process, followed by a thermo elastic plastic stress field, predicting deformed shapes of plate is very difficult and complex problem. In this paper, neural network model o3r solving the inverse problem of metal forming is proposed. The backpropagation neural network systems for determining line-heating positions from object shape of plate are reported in this paper. Two cases of the network are constructed-the first case has 18 lines which have different positions and directions and the second case has 10 parallel heating lines. The input data are vertical displacements of plate and the output data are selected heating lines. The train sets of neural network are obtained by using an analytical solution that predicts plate deformations in line heating process. This method shows the feasibility that the neural network can be used to determine the heating-line positions in line heating process.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.1
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• pp.48-59
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• 2018

This paper is mainly concerned with developing the formulae of predicting thermal deformation of steel plate due to multi-line heating. By investigating the results of line heating test and numerical analysis, reasonable heat flux model has been defined. Formulae of predicting the transverse shrinkage and the angular distortion as the dominant thermal deformation types in plate forming by line heating have been derived based on the results of line heating test and numerical analysis with varying plate thickness, heating speed and distance between torches. This paper illustrates how the derived formulae are used in investigating the effect of multi-line heating upon the thermal deformation and how they can be used in defining the limit distance with that there is no interacted effect between torches. This paper ends with describing the extension of the present study.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.4
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• pp.407-411
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• 2011

The technology of line heating has evolved in various methods. Among them, fossil fuels like ethylene gas and LPG(Liquid Petroleum Gas) are widely used due to their simple utility. In the meantime, the technology implementing high frequency for line heating has also been developed continually, but its manufacturing technology or application includes lots of problems by now. One of the main characteristics of line heating using conventional technolob'Y is the quenching effect followed by heating process. On the other hand, hydrox gas which is mixed by hydrogen and oxygen is a prominent candidate for an application without above shortcomings. Especially, it is found that line heating using hydrox gas is tremendously effective taking low cost as well as low noise. In this paper, a small cell with high efficiency which can minimize installing space is developed to deal with the problem installing in narrow place. Experiments to prove the validation, efficiency and effectiveness is carried out by characterizing in the line heating of steel. It is found that the energy saving of using hydrox gas for line heating is significant and that the deviation performance is reduced by 78~89%. Furthermore, the noise is also reduced as amount of 18.3% though the heating time is not too different.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.213-216
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• 2006

During the last decade several different methods have been proposed for the estimation of thermal deformations in the line heating process. These are mainly based on the assumption of residual strains in the heat-affected zone or simulated relations between heating conditions and residual deformations. However these results were restricted in the application from the too simplified heating conditions or the shortage of the data. The purpose of this paper is to develop a simulator of thermal deformation in the line heating using the artificial neural network. Two neural network predicting the maximum temperature and deformations at the heating line are studied. Deformation data from the line heating experiments are used for learning data for the network. It was observed that thermal deformation predicted by the neural network correlate well with the experimental result.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.3
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• pp.110-121
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• 2000

Gas heating, high frequency induction heating and laser heating can be used as the heat-source of line heating. Most of shipyards have been using the gas heating method for line heating. It is difficult to control the residual deformation of gas heating. High frequency induction heating is more feasible for the automation of line heating rather than the gas heating method since it is easy to control the magnitude of heat input. In this study, a numerical model of high frequency induction heating process is proposed for the application of the line heating. The simulation process of the induction heating is composed of the electromagnetic analysis, the heat transfer analysis, and the thermal deformation analysis.

• Journal of Ocean Engineering and Technology
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• v.20 no.4 s.71
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• pp.24-30
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• 2006

Different methods exist for the estimation of thermaldeformation of plates in the line heating process. These are based on the assumption of residual strains in the heat-affected zone, known as the method of inherent strains, or simulated relations between heating conditions and residual deformations. The purpose of this paper is to develop a simulator of thermal deformation in the line heating, using the artificial neural network. Curvature deformations for the plate-forming are investigated, which can be used as a prime deformation parameter in the process. The curvature of plates are calculated using the approximation of plate surface by NURBS. Line heating experiments for 11 specimens of different thickness and heating conditions were performed. Two neural networks predicting the maximum temperature and curvature deformations at the heating line are studied. It was concluded that the thermal deformations predicted by the neural network can be used in a line heating simulator, which is considered an attractive and practical alternative to the existing methods.

• Journal of Ocean Engineering and Technology
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• v.19 no.1 s.62
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• pp.33-38
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• 2005

It has been well documented that plate forming is one of the most important processes in shipbuilding. In the most shipyards, the line heating method is primarily used for plate forming. Since the heating process is carried out for the curved plate and not for the flat plate, a curvature effect on the final deformation must be considered in deriving the simplified prediction models for deformation. This paper investigates the effect of curvature along the heating line on the deformation of the plate. First of all, results of numerical analysis are compared with these of a line-heating test, to justify the elasto-plastic analysis procedure for the present study, which shows good agreement. Then, the present numerical procedure is applied to flat and curved plate models, to investigate the curvature effect on the heat transfer characteristics and deformation by line heating.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.2
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• pp.69-80
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• 2002

Sequential process of roll-bending and line heating has been used to deform the curved hull-plates in shipyards. A growing interest for the mechanization or automation of the line heating process has been noted. Relations between heating conditions and residual deformations are important components needed for the mechanization. The residual deformations are investigated by using a thermal elastic-plastic analysis based on the finite element analysis(FEA). Several experiments are also performed to examine the validity of the results of FEA. The input parameters of line heating are suggested by dimensional analysis of line heating. The dimensional analysis can extract the primary input-parameters of line heating. The relations between the heating conditions and the residual deformations are set up by multi-variate analysis and multiple-regression method. This study suggests a method for the relation between the heating conditions and the deformations lying under the line heating.

• International Journal of Ocean System Engineering
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• v.1 no.1
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• pp.46-51
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• 2011

In a line heating process for hull forming, the phase of the steel transforms from austenite to martensite, bainite, ferrite, or pearlite depending on the actual speed of cooling following line heating. In order to simulate the water cooling process widely used in shipyards, a heat transfer analysis on the effects of impinging water jet, film boiling, and radiation was performed. From the above simulation it was possible to obtain the actual speed of cooling and volume percentage of each phase in the inherent strain region of a line heated steel plate. Based on the material properties calculated from the volume percentage of each phase, it should be possible to predict the plate deformations due to line heating with better precision. Compared to the line heating experimental results, the simulated water cooling process method was verified to improve the predictability of the plate deformation due to line heating.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.6
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• pp.65-74
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• 2004

The inherent strain method is known to be very efficient in predicting the deformation of steel plate by line heating. However, in the actual line heating process in shipyard, the rapid quenching changes the phase of steel. In this study, In order to consider additional effects under phase transformation, inherent strain regions were assumed to expand. Also, when calculating inherent strain, material properties of steel in heating and cooling are applied differently considering phase transformation. In this process, a new method which can reflect thermal volume expansion of martensite is suggested.8y the suggested method, it was possible to predict the plate deformations by line heating more precisely.