Effect of Heating Spacing on Deformation Distribution of Line Heating Process

Abstract

Ship hull plate forming with line heating technique is an important process in the shipbuilding industry. An automatic line heating control system needs an accurate database of various processing parameters. In this study, a numerical model, calibrated and verified using experiment results, was used to study the deformation distribution of a plate corresponding to different heating line spacing. This paper presents the results based on a single-torch and multiple-torch process. The deformation distributions in the heating and nonheating regions were analyzed. The impacts of coupling effect among heating lines were deliberated. 1. Introduction Line heating is an efficient plate forming process for many applications, such as ship hull forming, molding car body, and other curved objects. In the shipbuilding industry, this method is mainly used to create double-curved ship hull plates, especially for those plates near the bow and stern. Line heating is a complex nonlinear thermal process that involves thermodynamics, elastic-plastic mechanics, and metallurgy. Many researchers have conducted studies on the mechanism of line heating process to predict the final shape of the metal plate according to the heating conditions and mechanical properties of the plate (Moshaiov & Vorus 1987; Ueda et al. 1994a, 1994b, 1994c; Ji & Liu 2001); others performed numerical analysis with thermal elastic-plastic models to determine the parameters in line heating process (Jang et al. 1997; Yu et al. 1999,2001; Yu 2000; Wang et al. 2006). Many experimental works were carried out to verify the thermal elastic-plastic models (Moshaiov & Shin 1991; Liu et al. 2006; Zhou et al. 2014a). The effects of parallel and cross heating lines were discussed recently (Zhou et al. 2014b; Vega et al. 2015). Residual stress among the steel plate was studied to reveal the relationship of different heating conditions. Different heat sources have been used in line heating process, and they include gas torch(Tomita et al. 2001; Jong & Jong 2003), laser beam (Kyrsanidi et al. 1999), welding arc (Kitamura et al. 1996), and high-frequency induction heating (Ogawa et al. 1994; Lee & Hwang 2014). In all heat sources, gas torch is most frequently used as it was and still is the cheapest and most readily available heating source in most shipyards.