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Influential Factors Affecting Inherent Deformation During Plate Forming By Line Heating (Report 5) - The Effect of Water Cooling
Vega, Adan (Department of Mechanical Engineering, Technological University of Panama) | Nawafune, Masashi (Graduate School of Engineering, Osaka University) | Tango, Yoshihiko (IHI Marine United) | Ishiyama, Morinobu (IHI Engineering Marine) | Rashed, Sherif (Joining and Welding Research Institute, Osaka University) | Murakawa, Hidekazu (Joining and Welding Research Institute, Osaka University)
In plate forming by line heating the usage of water as a cooling source is common. However, the relationship between water-cooling and plate deformation is not well established. This reduces the possibility of automating the process. In order to solve this problem, the influence of the rate of cooling on inherent deformation is first examined. Then, the inherent deformation produced by line heating is studied in detail. Finally, the relationship between inherent deformation and heating condition is recorded into an inherent deformation database. This database can be used to directly predict inherent deformation due to line heating and therefore enable the automation of the process. INTRODUCTION In plate forming by line heating, water-cooling is usually used due to its effectiveness in increasing plate deformation. However, the mechanism of forced cooling such as water cooling is highly complex and it is not fully understood. Therefore, it is necessary to create a method to predict the influence of water-cooling on plate deformation and therefore, enable the usage of automatic machines. Although there have been many papers reporting the line heating method, very few papers are dealing with the effect of water cooling on deformation of plates due to line heating, [e.g. Satoh, Matsui, Terai and Iwamura (1970), Jamg, Kim, Ha and Lee (2005), Ji, Yujun, Zhuoshang, Yanping and Jun (2006), Ha and Jang (2007)]. Not a clear relationship between water-cooling and deformation of plates due to line heating has been found yet. Various attempts have been made to understand the mechanism of heat transfer in pool boiling (the key to explain the influence of water-cooling on line heating process), [e.g. Davidson and Schueler (1960), Han and Griffith (1965), Mikic and Rohsenow (1969), Judd and Hwang (1976), Haramura and Katto (1983), Liu and Wang (2001), Wu, Yang and Yuan (2002), etc.]. However, the calculation of the convection coefficient is a difficult problem and cannot be described by using a single relationship.
Influential Factors Affecting Inherent Deformation During Plate Forming By Line Heating (Report 4) - The Effect of Material Properties
Vega, Adan (School of Mechanical Engineering, Technological University of Panama) | Tango, Yoshihiko (Morinobu Ishiyama, IHI Engineering, Marine) | Rashed, Sherif (Joining and Welding Research Institute, Osaka University) | Murakawa, Hidekazu (Joining and Welding Research Institute, Osaka University)
A 3-D thermal-elastic-plastic finite element analysis is performed to investigate the influence of temperature dependent material properties on prediction of inherent deformation due to line heating when numerical analysis by FEM is used. First, the temperature dependent material properties are defined. Variation with different degree was introduced and the resulting inherent deformation is then compared. Meanwhile, the other properties and process parameters are kept unchanged. Accordingly, the influence of various material properties on inherent deformation is revealed and discussed. It is found that the temperature dependent material properties play a key role on prediction of inherent deformation. Finally, conclusions of this numerical study are outlined. INTRODUCTION The plate forming using gas torch, induction heating or more recently laser heating is one of the most important forming processes actually used in shipyards. However, the line heating process is far to be fully automated, causing delays in the production line. The main reason of this is due to the fact that the relation between applied heat and final plate deformation, the key to automate the process, is too complicated to analyze by using simple mechanical models. In order to find a relation between these two parameters, it is necessary to consider other influential factors affecting the process such as the geometry of the plate, the cooling condition, the location of the heating line, multiheating lines, heat-induced curvature, residual stresses and inter-heating temperature [Vega et al. (2007), Vega et al. (2008), Vega (2009)]. The authors aim to propose a practical and accurate method to predict deformation of actual size plates such as those used in shipbuilding. As a fundamental component of this method, a line heating inherent deformation database is necessary. This inherent deformation database besides being mainly dependent on primary factors such as the plate thickness, the speed of heat source and the heat input, it also takes into account secondary factors such as the geometry of the plate, the cooling condition, the location of the heating line, multi-heating lines, heat-induced curvature, residual stresses, and inter-heating temperature.