• Transactions of Materials Processing
• /
• v.27 no.4
• /
• pp.236-243
• /
• 2018

A multi-point forming die (MPFD), which has been used for producing curved plates, is capable of forming various curved plates with just one MPFD. However, in real industries, an MPFD is difficult to be adopted since the structural properties, punch strength, elastic recovery correction and dimensional accuracy become problems. In order to overcome these problems, the hot multi-point forming die (HMPFD) was proposed in this study. This HMPFD commonly provide more less spring-back and forming load than conventional MPFD. Nevertheless, this process is very difficult to form the curved plate, because the final curved shape of the plate depends on many process variables such as the punch/nozzle arrangement (height and distance), the radius of punch, contact conditions between plate and punch. In this study, the forming characteristics of HMPFD and conventional MPFD are compared with each other through the finite element analysis.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2009.10a
• /
• pp.289-292
• /
• 2009

The line array roll set process, as one of many kinds of incremental forming processes, is a continuous process in which a flat metal plate is formed into a singly or doubly curved plate through successive passes of forming rolls. It was found that the curvature level of the formed plates in the previous study was well over the curvature required in shipyards. This fact shows that the LARS method has considerable potential for shipbuilding applications. In a shipbuilding yard, hull forming is an important fabrication process in which flat plates are deformed into singly or doubly curved plates. The major purpose of the present study is to estimate experimentally the general applicability of the line array roll set process for the manufacture of ship hull plates. In this study, the target shapes are selected through investigation of the shape classification of ship hull plates that comprise a certain vessel. Forming processes for twisted shapes are analyzed with the finite element method (FEM). Finally, the results of experimental work for two types of target shapes are presented.

• Transactions of Materials Processing
• /
• v.23 no.8
• /
• pp.507-512
• /
• 2014

The objective of the current investigation is to establish techniques in micro pattern forming operations of polymeric circular tubes by using hydrostatic pressing. This method was developed and successfully applied to the micro pattern forming on polymeric plates. The key idea of the new technique is to pressurize multiple vacuum-packed substrate-mold stacks above the glass transition temperature of the polymeric substrates. The new process is thought to be a promising micro-pattern fabrication technique for two reasons; first, (hydro-) isostatic pressing ensures a uniform micro-pattern replicating condition regardless of the substrate area and thickness. Second, multiple curved substrates can be patterned at the same time. With the prototype forming machine for the new process, micro prismatic array patterns, 25um in height and 90 degrees in apex angle, were successfully made on the PMMA circular tubes with diameters of 5~40mm. These results show that this process can be also used in the micro pattern forming process on curved plates such as circular tube.

• Transactions of Materials Processing
• /
• v.21 no.7
• /
• pp.432-440
• /
• 2012

In this article, the design of the flexible forming process considering die shape compensation using an iterative over-bending method based on numerical simulation was conducted. In this method, the springback shape obtained from the final step of the first forming simulation is compared with the desired objective shape, and a shape error is calculated as a vector norm with three-dimensional coordinates. The error vector is inversely added to the objective surface to compensate both the upper and lower flexible die configurations. The flexible die shapes are recalculated and the punch arrays are adjusted according to the over-bent forming surface. These iterative procedures are repeated until the shape error variation converges to a small value. In addition, experimental verification was conducted using a 2000-kN flexible forming apparatus for thick plates. Finally, the configuration of the prototype obtained from the experiment was compared with the numerical simulation results, which had springback compensation. It is confirmed that the proposed method for compensating for the forming error could be used in the design of flexible forming of thick-curved plates.

• Journal of Ocean Engineering and Technology
• /
• v.19 no.1 s.62
• /
• pp.33-38
• /
• 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 Ocean Engineering and Technology
• /
• v.23 no.1
• /
• pp.135-139
• /
• 2009

In the line heating for the plate forming of a ship's hull, an in line assessment of completion is necessary for an automated production system. In the current curved plate forming process, a fabricated plate is compared to a template that is made in the mold loft and is used for the determination of the heating line for the next step. In this paper, a new method is presented for the in line assessment of completion for curved plate forming. This method uses a 3-D scanner. For the registration of the scanned data for a surface and the target surface, the ICP (Iterative Closest Points) method was adopted. A computer program was developed to carry out the registration, check for similarities, visualize the surface, and control the results. This program was applied to a sample curved plate forming process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.10a
• /
• pp.152-155
• /
• 2005

A method of three-dimensional curved surface generation was studied for multi-point dieless forming (MPDF) in the shipbuilding industry. Three-dimensional coordinates of punch elements were obtained from objective surfaces using a proprietary CAD program. MPDF surfaces were generated by adjusting the height of punch elements in accordance with the coordinates. Some problems, such as collision of punch elements and contact between plates and punch bodies, were anticipated from the analysis of the results. A twisted surface was formed successfully by MPDF in a laboratory scale, which suggests possibility of application of the technology to the shipbuilding industry.

• Transactions of Materials Processing
• /
• v.19 no.2
• /
• pp.120-126
• /
• 2010

The line array roll set(LARS) process, as one of many kinds of incremental forming processes, is a continuous process in which a flat metal plate is formed into a singly or doubly curved plate through successive passes of forming rolls. It was found that the curvature level of the formed plates in the previous study was well over the curvature required in shipyards. This fact shows that the LARS method has good potential for shipbuilding applications. The major purpose of the present study is to estimate experimentally the general applicability of the line array roll set process for the manufacture of ship hull plates. In this study, the target shapes are selected through investigation of the shape classification of ship hull plates that comprise a certain vessel. Forming processes for twisted shapes are analyzed with the finite element method(FEM) and the results of experimental work are presented. On the basis of the experimental and numerical results, the LARS process is applied to the production of real outer hull plates of a small patrol ship.

• Journal of the Society of Naval Architects of Korea
• /
• v.48 no.6
• /
• pp.528-538
• /
• 2011

As a forming method for curved hull plates more efficient than the flame bending, mechanical bending using multi point press forming and die-less forming is discussed in this paper. the mechanical forming is a flexible manufacturing system for automatically forming of hull parts. It is especially suited to varied curved parts. This paper discusses a multiple point pressing machine composed of a pair of reconfigurable punches in order to achieve the rapid forming of curved hull plates using division forming and presents how forming information is obtained from the given design surface. Although the mechanical forming can be efficient in the metal forming, spring back after pressing is a phenomenon which must be carefully considered when quantifying the process variables. If the spring back is not accurately controlled, the fabricated shell plate cannot meet assembly tolerance. This paper describes the principles to calculate the proper stroke of each punch at the divided areas. the strokes are determined by an iterative process of sequential pressing and spring back compensation from an unfolded flat shape to its given design surface. FEA(finite element analysis) is used to simulate the spring back of the plate and the IDA(iterative displacement adjustment) method adjusts the offset of pressing punches from the deformation results and the design surface. The shape deviations of two surfaces due to spring back are compensated by integrated system using FEA and IDA method. For the practical application, It is aimed to develop an integrated system that can automatically perform the compensation process and calculate strokes of punches of the double sides' reconfigurable multiple-press machine and some experimental results obtained with mechanical bending are presented.

• Transactions of Materials Processing
• /
• v.18 no.7
• /
• pp.556-564
• /
• 2009

Flexible forming process for sheet material using reconfigurable die is introduced based on numerical simulation. In general, this flexible forming process using the reconfigurable die has been utilized for manufacturing of curved thick plates used for hull structures, architectural structures and so on. In this study, numerical simulation of sheet metal forming process is carried out by using flexible dies model instead of conventional matched die set. The numerical simulation and experimental verification for sheet metal forming process using a flexible forming machine that is more suitable for thick plate forming process are carried out to confirm the appropriateness of the simulation process. As an elastic cushion, urethane pads are utilized using hyperelastic material model in the simulation for smoothing the forming surface which is discrete due to characteristics of the flexile die. In the flexible forming process for sheet metal, effect of a blank holder is also investigated according to blank holding methods. Formability in view of occurrence of dimples is compared with regard to the various punch sizes. Consequently, it is confirmed that the flexible forming for sheet material using urethane pad has enough capability and feasibility for manufacturing of smoothly curved surface instead of conventional die forming method.