Line Heating Process Research Articles

Selection of Heating Lines in the Line Heating Process for Steel Plates Using Faster R−CNN

Selection of Heating Lines in the Line Heating Process for Steel Plates Using Faster R−CNN

Effect of Line-Heating on the Microstructural and Mechanical Characteristics of 320-MPa-Grade High-Strength Hull Plates

This study examined the effect of the line-heating process on the microstructure and mechanical properties of 320-MPa-grade high-strength steel designed for low-temperature applications. The samples were heated thrice to the maximum temperature condition of 900 ℃ prior to air cooling or water quenching. Tensile strength and Charpy impact toughness tests were performed to understand the variation in the mechanical characteristics across the thermal histories. The decrease in the tensile strength of the air-cooled specimen was attributed to grain growth and phase transformation caused by slow cooling, while the water quenched specimen exhibited grain refinement. The experimental results indicated that the line-heating process was suitable because all the specimens with various thermal histories satisfied the international classification standard.

Deformation Behavior of Aluminum Alloy Plate Under Electromagnetic Force Assisted Line-Heating Process

As a new technique for the deformation of aluminum alloy plate with complex curved surface which is used in shipbuilding, electromagnetic force assisted line-heating process, or EFALH for short, can promote forming efficiency and produce anticipated curved surface within the range of temperatures required in production. For a start, the process unit and experimental scheme for EFALH were introduced in the article. After the experiment, it was confirmed that the electromagnetic force do have auxiliary effect on the deformation of aluminum alloy plate. Then, for the EFALH process, three-dimensional numerical simulation was performed, and the simulated results were verified by experimental data. Influence on the deformation process caused by the difference in the time and current amplitude of electromagnetic force was studied through numerical simulation. At last, the deformation behavior of the plate under EFALH process has been analyzed from two perspectives, namely the periodism of pulsed electromagnetic force and the loading and unloading procedure in the load cycle caused by electromagnetic force.

Line heating process parameter forecasting method based on optimization concept

In ship construction, line heating is a necessary process for forming ship plates with complex curvature. The determination of line heating process parameters has a significant impact on the accuracy of the process and the efficiency of shipbuilding. However, previous studies on this subject only stay at the level of predicting deformation, which has not meet the actual processing production requirements. In this paper, a new idea of forecasting line heating parameters proposed. Firstly, an Radial Basis Function (RBF) proxy model between processing parameters and deformation was constructed based on experimental data, and then the reliability of the proxy model is verified. The optimization objective for proxy model was set as the minimum difference between the final deformation and the target deformation. Meanwhile, an improved Multi-Objective Particle Swarm Optimization (MOPSO) method was employed to search the optimal-set of processing parameters with non-dominated solutions. The performance of the optimized parameter set was ranked by using the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS), and the processing parameters combination ranking first was selected as the parameter forecasting result. The results showed that the predicted processing parameters have some reference for the practical engineering.

Approach to Automation of Line Heating by Combination of Reinforcement Learning and Finite Element Method Simulation

Abstract In recent years, ship hulls have very complicated shapes in order to reduce frictional resistance and wave resistance during navigation. In particular, in the bow and stern, curved skin plates with complex shapes are used. Line heating is used to produce such complex shapes. Line heating is a bending technique using plastic deformation due to heating. The relationship between the heat input and the deformation is nonlinear, which may lead to difficulty in making a heating plan for forming the target shape. Thus, skilled workers are necessary in line heating, and the work time and dimensional accuracy depend on their skills. Another problem is the transfer of this technique to future generations. In order to overcome these problems, automation of the line heating process has been investigated urgently. On the other hand, artificial intelligence (AI) technology has been rapidly developed in recent years. An AI system can deal with nonlinear relationships and ambiguous feature quantities, which are difficult to express mathematically. By using AI, automation of the planning of the heating line can be expected. The purpose of the present study is to obtain the optimal heat input conditions for forming an arbitrary shape in line heating. In order to accomplish this, we constructed an AI system that integrated deep layer reinforcement learning and line heating simulation. The proposed system was applied to the formation of fundamental shapes of line heating, including the bowl shape, the saddle shape, and the twisted shape. As a result, the proposed system was found to be able to generate heating plans for these shapes with fewer heating lines.

CHARACTERIZATION AND ANALYSES ON RESIDUAL STRESS AND DEFORMATION DISTRIBUTION IN LINE HEAT PROCESS

Line heating is an important plate bending process that has been adopted in shipyards for more than 60 years. This paper presents the results of a numerical and experimental study on the residual deformation and stress distribution in the plate forming process using the line heating method. In this paper, a finite element model was used to simulate the heating process, and the model was validated using experimental results. The model was then used to analyze the deformation and stress distributions in the heating and non-heating region. The impact of line heating and sequence of heating on both sides of a steel plate was discussed. The findings of the study show that the compression stress generated help to increase the shrinkage of line heating process. This study presents a valuable reference for similar thermal process.

NUMERICAL AND EXPERIMENTAL STUDY ON PLATE FORMING USING THE TECHNIQUE OF LINE HEATING

Nowadays manual and experiential technique patterns of line heating process could not meet the requirement of modern shipbuilding. Therefore, the automatic forming method is being an active research topic in manufacturing. An accurate and practical predicting method is an essential part of the automatic plate forming system. In the present work a numerical elasto-plastic thermo-mechanical model has been developed for predicting the thermal history and resulting deformation and residual stress field of line heating process. A moving Gaussian distributed heat source was used in the modelling to create a realistic simulation of the process. The transient temperature distributions were predicted using temperature-dependent material properties. The deformation and residual stress field were predicted based on the transient temperature distributions of line heating. Experiments were conducted to prove the validity of the numerical thermo-mechanical model. The final numerical results of temperature, deformation and residual stresses are in good agreement with experiment results. The proposed method presents a valuable reference for the study of similar thermal process.

Development of manufacturing support system for ship curved shell plate using laser scanner

Curved shell plates used for ship hull have complicated three-dimensional curved surfaces, especially at the bow and stern. The manufacturing processing of ship curved shell plates have been carried out for many years by the tacit knowledge and experience of skilled workers by using wooden templates, and this processing is heavily dependent on individual skills. Formalization and systematization of this manufacturing process are desired．This paper proposed a system to enable skilled workers to process curved shell plates to the desired shape without using wooden templates. Especially, we analyzed a curvature error evaluation method, which is a previous work, and clarifies that the integral value of the curvature error should be used to determine the heating position at the same level as the skilled worker’s decision-making. In addition, total information system was developed for supporting skilled workers decision-making by using several calculation methods.In the case study, we applied the proposed system to an actual bending curved shell plate process. It was confirmed that the proposed system could provide a satisfactory level of decision-making support of the line heating process in the production field of a shipyard.

Analisa Pembengkokan Pelat dengan Metode Line Heating

One method of bending the plates in hull construction can be done either by conventional or by line heating method. The method of line heating has several advantages, such as lesser initial investment and can be used for three dimension form. This research is focused to obtain the relation between the parameter in line heating process and the conceited of plate curve that produced. With the aim of the curvature of structural changes caused by the heat given during the plate bending process it can be seen for the shipbuilding fabrication process. From the results of this study obtained data on line heating conditions on plates with a thickness of 10 mm (plates A and B) obtained the maximum curvature height is 11.1 mm at a heating speed of 8 mm / s and a heating temperature of 3850 C. Furthermore, the amount of heat input that is applied to material 3327.47 Joules / sec and due to efficiency at 1697,001 Joules / sec.
 Keyword: Line Heating Method, Line Heating Parameter, Curve Heights

Effect of Plate Curvature on Heat Source Distribution in Induction Line Heating for Plate Forming

Line heating is an essential process in the formation of ship hull plates with a complex curvature. Electromagnetic induction heating is widely used in the line heating process. In electromagnetic induction heating, the shape of the coil and the air gap between the inductor and workpiece could influence the heat source distribution. Moreover, in the line heating process, the change of curvature of the plate will cause a change of the air gap of the inductor. Magnetic thermal coupling calculation is an effective method for simulating induction heating. This paper used the finite element method to calculate the distribution of heat sources in different initial plate curvatures and coil widths. The changes in heat source distribution and its laws were investigated. The results show that when the coil width is less than 100 mm, the effect of plate curvature on heat source distribution and strain distribution is not apparent; when the coil width is greater than 100 mm, the plate curvature has a visible effect on the heat generation distribution. In the case of a curvature increasing from 0 to 1 and a coil width equal to 220 mm, the Joule heat generation in the center of the heating area is reduced by up to 21%.

On Rough Set-Based Modeling and with Application to Process Decision for Forming Plate by Line Heating

In shipbuilding, forming plate by line heating is atypical complex manufacturing process involving many uncertain factors, so it is difficult to establish an accurate mathematical model. How to establish a knowledge model that can reflect technological laws is the key to the development of an intelligent decision system for forming plate by line heating. In this article, rough set (RS) theory is applied to the modeling of the line heating process. By defining variable-inclusion RSs, an algorithm of knowledge reduction is proposed, which enhances the noise immunity and fault tolerance of the model, and improves the efficiency of knowledge acquisition. Through introducing fuzzy logic, a method of modeling the line heating process based on RSs and fuzzy logic is proposed, which effectively extracts the technological rules of plate formation. Finally, rapid decision-making for process parameters is implemented by fuzzy inference technology. 1. Introduction For some complex manufacturing technologies in modern shipbuilding, such as line heating and welding processes, it is difficult to establish an exact mathematical model because of high nonlinearity, multivariable coupling, and uncertainties of the system. With the development of computer technology and artificial intelligence, soft computing methods such as artificial neural networks, genetic algorithms, fuzzy logic, and rough set (RS) theory have been applied successively in ship manufacturing process modeling, which shows good prospects for intelligent technology in shipbuilding. Shin et al. (1999) at Seoul National University used a single-curvature plate model to simulate the formation of saddle-type shells and deduce the technological parameters of line heating by an artificial neural network. They also proposed a comprehensive algorithm for automatically curving plate by line heating, and further developed an application system that can simulate the deformation of double-curved plates (Shin et al. 2004a, 2004b). Liu et al. (2006) applied a hierarchical genetic algorithm to optimize the technological parameters of an automatic line heating process. In the field of ship welding, fuzzy logic technology has been used to establish a fuzzy model of the relationship between welding variables and weld forming-parameters (Su 2009). Feng (2012) set up a knowledge base of a ship-welding process by a RS method and then implemented ship-welding production design through uncertainty reasoning. Based on RS theory, Chen and Lv (2013) developed a data-driven knowledge base for quality control of ship hull welding.

Analysis of Forming Regularity in Line Heating Process for Curved Hull Plate by Considering the Plate Deflection

Nowadays in most shipyards, line heating techniques are widely used in the forming process of hull plates. The precision and efficiency of the process are greatly influenced by the determination of technical parameters, including heating length, heating velocity, and the arrangement of heating line. Previous studies on this, which considered only local shrinkage, produced large errors in the calculation of thick and large curvature plates because the whole deformation was ignored. In this article, new mathematical formulas are proposed to indicate the relationship between the whole deflection and shrinkage during the plate-forming process by line heating. The numerical models were established based on the thermoelastic plastic finite element method considering the deflection. The reliability of the numerical models was verified by the comparison of temperature fields and displacement. Based on the analysis of forming regularity, a new concept named influence factor of deflection (IFD) was proposed from the analysis between deflection and shrinkage. The formulas were derived, which establishes the relation between the IFD and technical parameters. Finally, the experimental results showed that the relative percentage error is 5.13% for IFD, and the forming formulas were verified. The research lays a foundation for the technique of parameter prediction of thick and big curvature plates considering the deflection. 1. Introduction The procedure of lofting, marking-off, pretreatment of steel plates, cutting, and welding has been automated in shipbuilding. Hull plate forming is the bottleneck of shipbuilding. There are numerous curved hull plates that need to be formed within the shipbuilding industry. Precision and efficiency are the technical difficulties in hull plate forming. It is very important to realize the automatic forming of curved hull plate. Line heating is an important method in hull plate forming, which mainly relies on the experience of the workers (Seong et al. 2013). The general processes are as follows. First, the technical parameters of hull plate forming are obtained based on the workers' experience. Then, hull plate forming is carried out manually by the workers. Last, plate forming quality is detected by using detection templates or a detection box. If plate forming cannot meet the requirements of the standards, the workers need to reform the plate, until it can meet the requirements. These procedures cause low efficiency and great fluctuation in forming quality. Therefore, it is essential to perform automatic line heating research.

Effect of Heating Spacing on Deformation Distribution of Line Heating Process

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.

A simplified heat source model for thick plate bending via high-frequency induction line heating

ABSTRACTCoupled electromagnetic-thermal methods have been widely used to simulate the induction line heating process. However, the rigorous mesh requirement for accurate magnetic calculation is not suitable for large-scale simulation, such as the plate bending calculation. This paper introduces an efficient and accurate approach to simplify a heat source to enable the rapid estimation of thick plate bending with induction heating. First, based on the coupled method, which can consider temperature-dependent material properties, numerical studies on power distribution are performed to verify the feasibility of the simplified method. Second, from the first step of the coupling analysis on a small yet accurate sample, a simplified Gaussian surface heat source is obtained and then applied to a large-scale plate. Finally, the results obtained from the proposed method and the current coupled method are compared with experimental results. The comparisons reveal that the proposed method can reduce the duration of the calculation considerably while maintaining the same level of engineering precision.

A New Method for Production of Double-Curvature Dome-Shaped Part: Statistical Analysis of the Effects of Process Parameters on the Radius of Curvature of Obtained Dome Shape

A New Method for Production of Double-Curvature Dome-Shaped Part: Statistical Analysis of the Effects of Process Parameters on the Radius of Curvature of Obtained Dome Shape

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).

Evaluation Method for Ship Hull Plates’ Process Molding

The evaluation procedure is an important step for the ship hull plates automatic processing, which serves as a basis for secondary processing. In this paper, an evaluation method was proposed, based on the experienced workers' knowledge. The design surface and the measured surface were registered by transforming to the new coordinate system. Then the profile errors were evaluated and decomposed into three directions: transverse, longitudinal, and torsional. Finally, the experiment results shown that the evaluation indexes, which were based on the errors decomposed result, can be served as the basis for secondary processing of the ship hull plates. 1. Introduction Ship hull plates are thick large steel plates with arbitrary threedimensional (3D) shapes. Usually, the steel plates are plastically deformed to the design shape by line heating process. And the shapes of the machining plates are evaluated by the wooden bending templates, which are generated by ship's design data. Experienced workers can evaluate the transverse bending, longitudinal bending, as well as torsional angle of the plates by this process, and get the essential factual basis for the secondary processing. However, this process has no clear-cut methodology, the evaluation results and the secondary processing plan are heavy, depending on the tacit knowledge, skill, and experience of the craftsmen during the line heating processing (Woo-Jae et al. 2010; Hiekata et al. 2011; Seong et al. 2013; Sun et al. 2013). For ship hull plates profile error evaluation, Hiekata et al. (2011) had put forward an accuracy evaluation system, using 3D laser scanner to measure the ship hull plates, and then evaluated the displacement errors by comparing the measured surface with the design surface. This system had achieved digital evaluation, but the evaluation indexes were difficult to guide the secondary processing. Sun et al. (2013) evaluated the ship hull plates by the virtual templates, and generated the processing plan, according to the evaluation results. Nevertheless, this method only evaluates the longitudinal bending and torsional condition. it still needs to be improved. Also, other researchers (Wen et al. 2013; Liu 2014; He et al. 2015; Nasri et al. 2015) had put forward various evaluation methods, but the purposed methods were aimed to improve the evaluation accuracy, seldom consider the line heating process. Thus, these methods have failed to provide the factual basis for the secondary processing.

Experimental study of springback behavior in incremental bending process

Manufacturing complicated and thick ship-hull plates at reasonable price and efficiency has always been a challenge in shipbuilding industry. One widely used method is line heating process, which is not only labor intensive but also ineffective. Recently many flexible forming processes have been developed while they all have avoidable disadvantages. In order to reduce the forming force, our group proposed one flexible incremental bending technology, during which the flat blank was bended into the required shape by gradually stamping at various positions. During the incremental bending process, the minimum energy method is used to determine the proper loading path. However, there is huge springback phenomenon after each bending. The shape change after each springback process should be considered in the loading path determination to make sure the accurate shape can be obtained.Here in this paper, the springback behavior of the carbon steel Q235 during the incremental bending process was investigated by experiments. In the first stage, the flat plates were bended several times at the same position while the final bending depth is the same, the final bending shapes after springback were compared to each other to investigate the influence of loading path on the springback behavior of the material. In the second stage, the flat plates were bended once at various positions and bending depths to study the springback behavior in one step bending process. It was found that loading path has little influence on the springback behavior, so during the incremental bending process, the springback law obtained from each single bending process can be used to combine with the minimum energy method to obtain the proper punch moving trajectory.

Thermo-mechanical analysis of line heating process by an efficient and accurate multi-level mesh refining method

Plate forming technique with line heating is indispensable for producing curved plates of ship hulls. The present study aims to reduce the tremendous computation time in transient thermal-mechanical analysis of line heating with a moving heat source. The dynamic mesh refining method developed by the authors was extended to simulate large scale plate forming process by line heating. The current method features an element orientation-based multi-level refinement scheme which greatly reduces the number of degrees of freedom in a finite element model. Meanwhile, the background mesh introduced in the dynamic mesh refining method was used to save and update global solution. Accuracy of the refining method was demonstrated by parallel line heating on a square plate with available experimental results. Furthermore, the performance of proposed method was examined through comparison with a general purpose commercial code. It was confirmed that, the new code has comparable accuracy while the computational efficiency is more than one order higher than the commercial code. The transient thermo-mechanical analysis of line heating on a large-scale plate was accomplished within a realistic time.

Numerical analysis and experimental research of triangle induction heating of the rolled plate

In shipyard, triangle heating technology with irregular multi-heating paths and highly concentrated heat input is used to form a curved plate, especially a concave type plate. Compared with line heating process with simple line segment path, its main purpose is to get a bigger contraction deformation at the plate edge. Hence, triangle heating technology is important for most shipyards to increase hull-forming productivity and study the automation. This paper focuses on the moveable triangle induction heating technology. An electromagnetic coupling finite element model is built to simulate the moveable triangle induction heating process and reveal the temperature characteristics and deformation behavior. The results of the simulation are compared with those obtained from experiments and show good agreement. It demonstrates that the numerical model used in this study is effective for simulating triangle heating for the steel plate forming process in shipbuilding. With the numerical model, the paper further investigates the effect of heating parameters on temperature and shrinkage deformation. These are traced here with a modified mechanical model whose results are in accord with the numerical results. This modified model can be applied to predict the edge shrinkage and explain the effect of heating parameters on transverse shrinkage.