• Journal of the Korean Society of Industry Convergence
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• v.21 no.6
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• pp.419-427
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• 2018

In case high strength steels are applied for press-formed automotive parts, it is very difficult to secure forming accuracy due to large springback compared to moderate strength steels. In this study, a repetitive step-wise forming analyses based on secant method was proposed as the die design method for mandrel(bending tool) for the 2-axis bending equipments. A bending die with circular mandrel was designed for the DP780 blow motor case of which diameter and thickness are 70.8mm and 2.0mm respectively. Forming tests were performed to verify the validity of established die design and the results were compared with that of conventional HGI(Hot galvanized iron steel) blow motor case. For additional improvement in forming accuracy, an elliptical mandrel was proposed and its validity was verified using forming analyses based on secant method.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.11
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• pp.89-96
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• 2016

The performance of anti-submarine sonar detection is required to improve by the development of submarine noise reduction technology. because of the need of an anti-submarine detection ability, known for superior beamforming performance, adaptive beamforming algorithms have been considered as an alternative beamforming algorithm of a conventional beamforming algorithm. In order to achieve improved performance by applying an adaptive beamforming algorithm to the sonar system, the adaptive beamforming algorithm applicability of system must be verified, To do this, the performance index for the system applicability must be established. In this paper, a tracking initiation probability of the adaptive beamforming algorithm and the conventional beamforming algorithm was calculated and the performance of both techniques was quantified, a system applicability of the adaptive beamforming algorithm was reviewed.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1142-1147
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• 2003

The formability of sheet metal appears better in incremental forming than in conventional forming. in this study, the effect of process parameters - tool type, tool size, feed rate, friction at the interface between tool and sheet, plane-anisotropy of sheet - on the formability was investigated by experiments and FEM analyses. it was found that the formability is improved when a ball tool of a particular size is used with a small feed rate and a little friction. Due to the plane anisotropy, the formability differs according to the direction of the tool movement. in this paper, details of the experimental procedures and the results obtained from the study are discussed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.11a
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• pp.15-22
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• 2002

To carry out perfectly the forming analysis of the extruding products, it is necessary that the friction boundary condition between dies and blanks should be worked out the accuate numerical friction models. But the numerical friction models adapting in the conventional Extrusion forming software may be large different from the actual conditions. Expecially, the use of the existing extrusion forming software is possible only in the limitted range owing to the unaccuracy of the high speed forming work. Therefore, tile prepare of this study is to develop the numerical friction model which describes the friction boundary condition mathematically well, to improve the accuracy of the extrusion farming analysis, and finally to expand the applying areas of the results.

• Transactions of Materials Processing
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• v.10 no.2
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• pp.123-129
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• 2001

This study is to investigate the effects of cold forming method with steel sheet of SCP3C to improve continuous productivity. Experiments were carried out in various working conditions, such as the number of stamping and the punch temperature. The effects of the punch temperature and the number of stamping on drawability of steel sheet of SCP3C as well as clearance and draw-in in the number of stamping were examined and discussed. More improvement of continuous productivity in case of cold stamping rather than by conventional stamping at room temperature is obtained. The optimum forming condition for drawing trunk floor panel of SCP3C is shown as the punch is cooled by coolant of $-5^{\circ}C$ and at the same time both the die and the blankholder are heated by stamping and frictional heat.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.22-25
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• 1999

A dynamic explicit finite element code for simulating sheet forming processes has been developed The code utilises the discrete Kirchhoff shell element and contact force is treated by a conventional penalty method. In order to reduce the computational cost a new and robust contact searching algorithm has been developed and implemented into the code. in the method a hierarchical structure of tool segments called a tree structure is built for each tool at the initial stage of the analysis Tree is built in a way to divide a trunk to 8 sub-trunk 2 in each direction until the lowest level of the tree(leaf) contains exactly one segment of the tool. In order to have a well-balanced tree each box on each sub level contains one eighth of the segments. Then at each time step contact line from a node comes out of the surface of the tool. Simulation of various sheet forming processes were performed to verify the validity of the developed code with main focus on he usefulness of the developed contact searching algorithm.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.134-140
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• 2000

Tube hydroforming is a relatively new technology compared to conventional stamping. thus there is little knowledge base that can be utilized for process and die design. To remedy this situation considerable research is now being conducted by many researchers on significant aspects of tube hydroforming technology including material selection pre-form design hydroforking process and tool design. in the tube hydroforming process we frequently experence many failure modes like wrinkling. buckling folding back and fracture under the improper forming conditions. In this paper forming limit for failure occurrence such as fracture and wrinkling is examined theoretically and the result is compared with Back's experimental result.

• Transactions of Materials Processing
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• v.8 no.2
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• pp.188-199
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• 1999

Semi-Solid Forming Process(Thixoforming, Rheocasting) is a novel forming process which has some advantages compared with conventional die casting, squeeze casting and hot/cold forging. In this study. Thixoforming process was selected as analysis processing in terms of billet handling and easiness of automation process. The Thixoforming process consists of reheating process of billet, billet handling, filling inot the die cavity and solidification of SSM part. In filling process, two rheology models which were Newtonian and Non-Nettonian model (Ostwald-deWaele)were verified with experimental results. The Ostwald-deWaele model shows the good agreement to the real flow and filling phenomena in die cavity. To give a boost the economical efficiency of Thixoforming process and to ensure the good forming result, reheating device coupled die set was proposed and the initial billet temperature for system that was found from experimental resluts. This study presents an overview of application of numerical analysis for simulation of semi-solid metal forming process to reduce the lead time for development of manufacturing part in industrial field.

• Transactions of Materials Processing
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• v.8 no.2
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• pp.160-168
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• 1999

This paper is concerned with the process sequence design of longneck flange forming by using cold extrusion with thick hollow pipe. The conventional hot forming process to produce a longneck flange is investigated by thermo-viscoplastic finite element method to observe the metal flow in detail and evaluate design requirements. Based on the results of simulation of the current hot forming process, design strategy for improving the process sequence are developed using the thick hollow pipe. The main goal is to obtain an appropriate improved process sequence which can produce the required product most economically without tensile cracking, workpiece buckling, and overloading of tools. Newly process condition such as semi-die angle, reductio ratio of cross-sectional area of axisymmetrical extrusion process. The final designed process can provide very useful guidelines to other flange forming industries.

• Transactions of Materials Processing
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• v.23 no.2
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• pp.103-109
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• 2014

Flexibly-reconfigurable roll forming (FRRF), which is a sheet forming process for multi-curved sheet metal, may solve both the economic and technical problems incurred in using a conventional die forming process. In the FRRF process, the multi-curved sheet metal is formed by different strain distributions on the sheet metal, and the reconfigurable rollers are used as tools during the forming. Therefore, a thorough investigation focused on the reconfigurable rollers is required for the realization of the FRRF process prior to the fabrication of FRRF machine. In the current study, a series of finite element simulations were conducted to study the load distributions experienced by the reconfigurable roller. In order to verify the shape design variables, the effect of the metal thickness on the curvatures of sheet is also presented.