A Review of Plate Forming by Line Heating

Line heating is a technique for incorporating curved shape on a plate by suitable means of heating with the help of suitable heat source. In this present study, an overall literature review on plate forming by line heating is addressed. In the present study, more emphasis is given especially on the line heating temperature field analysis, thermomechanical analysis, heating line generation, and development of compound curve surfaces along with soft computing approaches for the present technique. The present review article is subdivided into eight subdivisions. 1. Introduction The research activity in the process of line heating has started decades ago. Till date, less number of researchers have taken up the scope of line heating process for better control. Different methods are taken into consideration for understanding the mechanics of the process. The process is basically based on localized heating without exceeding the recrystallization temperature of the substrate material followed by normal cooling. The process of line heating is found to be most efficient and popular for various surface development activities; for that reason many attempt has been made by various shipyards across the world for implementing the line heating technique for plate bending operations. Some of them are Todd Pacific shipyard (Chirillo 1982); astilleros Esplanos (Spain) (Clausen 2000); Fincantieri (Italy); Daewoo (South Korea); Mitsubishi, IHI (Ishiyama et al. 1999), and NKK (Kitamura et al. 1996) in Japan; and Atlantic Marine Shipyards, NASSCO, and Norfolk Naval Ship Yard in the United States. This section is subdivided into important subgroups and a brief review is provided topic wise under these subgroups. 1.1. Categories of line heating process 1.1.1. Based on types of heat sources. Oxy fuel gas flame: It is one of the cheapest and readily available heat sources. For obtaining precise control over deformation, there should be ease of control on the amount of heat flux. Poor control of heat flux is obtained from mixed gases (for oxy fuel gas) as it is difficult to control the heat generation features resulting from the reaction of gases (Bae et al. 2009). It is also difficult to control as regards repeatability in gas amount and as regards keeping a constant distance between the gas torch and the plate (Clausen 2000). Induction heating: It allows for much precise control of the penetration of heat and depends on the frequency of induced electrical field (Biswas 2008). For knowing the feasibility of induction heating for line heating process various experimental studies and numerical calculations were carried out which revealed that plate bending in case of steel as a material can be achieved by induction heating (Zhang et al. 2011). Laser beam heating: It is one of the most precise controlled heating processes and also one of the most applicable techniques for forming of metallic sheet component (Dearden & Edwardson 2003). The process is similar to that of flame bending process but high precision can be obtained on the final end product, formed by this process. The process can be best suited for automation and combination with protective gas that reduces the risk of oxidation of the surface (Dearden & Edwardson 2003).