• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.254-258
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• 2008

Dimensional accuracy is very important quality in micro forged part, especially on forged part. Dimension of forged part is changed continuously during forging process. Loading, unloading and ejecting stage affects dimensional of the forged tool. The elasto-plastic material model for billet and elastic model for die were used to analyze these changes. At same time, the calculated results were compared and analyzed by the experiment on same conditions. From the experimental and analytical studies, we can calculated the amount of difference between die and forged part, that is 0.49% based on the die dimension. The dimensional change is smaller than that of general sized-forged part,0.6%.

• Transactions of Materials Processing
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• v.4 no.1
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• pp.28-38
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• 1995

An integrated process planning system can determine desirable operation sequences even if they have little experience in the design of multistage cold forging process. This system is composed of seven major modules such as input module, pre-design module, formability check module, forming sequence design module, forming analysis module, FEM verification module, and output module which are used independently or in all. The forming sequence for the part can be determined by means of primitive geometries such as cylinder, cone, convex, and concave. By utilizing this geometrical characteristics(diameter, height, and radius), the part geometry is expressed by a list of the primitive geometries. Accordingly, the forming sequence design is formulated as the search problem which starts with a billet geometry and finishes with a given product one. Using the developed system, the sequence drawing with all dimensions, which includes the dimensional tolerances and the proper sequence of operations for parts, is generated under the environment of AutoCAD. Several forming sequences generated by the planning system can be checked by the forming analysis module. The acceptable forming sequences can be verified further, using FE simulation.

• KSTLE International Journal
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• v.2 no.1
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• pp.80-84
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• 2001

The purpose of this paper is to show the result from the study to improve the formability and appearance which is important in the cold rolled strip, the coated strip and prepainted strip. Furthermore, to give appropriate surface roughness, shape of work roll for temper mill is also important. The strip has a greater peak counts and homogeneous roughness. This makes the prepainted surface smooth and consistent in appearance with good image clarity. Therefore, the surface roughness of the work roll is very important. The reason that surface roughness of the work roll is transferred to the strip surface is the rolling farce and tension at the temper rolling or cold rolling. This study is classified in order to get an accurate and homogeneous roughness. There are few papers published in this field, because its importance is not known and the proper operation of the machine is not generally well known. This paper investigates the correlation between strip surface roughness and the surface of the work roll. After studying the surface roughness and shape according to the texturing method for roll surfaces at temper rolling, the findings were as follows. Irregular surface roughness can be compensated with several paint coatings, but this also makes the quality deteriorate and manufacturing costs go up.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.83-90
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• 2004

The drawbead is one of the most important factors in sheet metal forming for automotive parts. So clarifying the friction characteristics between sheets and drawbead is essential to improve the formability of sheet metal. Therefore in this study, drawbead friction test was performed at various panels(cold rolled steel sheets, galvanized steel sheets, electrogalvanized coating steel sheets, electrogalvanized Zn-Fe alloy steel sheets and aluminum alloy steel sheets). Circular shape bead has been used for the test. The results show that friction and drawing characteristics were mainly influenced by the nature of zinc coating.

• Transactions of Materials Processing
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• v.11 no.5
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• pp.405-413
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• 2002

A process planning system for cold forging of non-axisymmetric parts of comparatively simple shape was developed in this study. Programs for the system have been written with Visual LISP in AutoCAD. Shape of the product must be drawn with the solid line and the hidden line, and with the plane and front view, as well. At the plane, the system recognizes the external shape of non-axisymmetric portions - the number of the sides of the regular polygons and the radii of circles inscribing and circumscribing the polygon. At the front view, the system cognizes the diameter of axisymmetric portions and the height of the primitive geometries such as polygon, cylinder, cone, concave, convex, etc. The system perceives that the list developed from the solid line must be formed by the operation of forward extrusion or upsetting, and that the list developed from the hidden line must be formed by the operation of backward extrusion. The system designs the intermediate geometries again by considering clearance between workpiece and die, and then finally the billet diameter, in reverse order from the finished product, on the basis of volume constancy and using the operations, the forming sequence, the number of operations and the intermediate geometries which were already designed. The design rules and knowledges for the system were extracted from the plasticity theories, handbook, relevant reference and empirical knowledge of field experts. Suitability of the process planning was analyzed using SuperForge of FVM simulation package. The results of analysis showed good formability.

• Design & Manufacturing
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• v.12 no.3
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• pp.60-65
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• 2018

The production of the automotive parts with the ultra high strength steel usually involves large amount of springback as well as fracture during the cold stamping process. Variable blank holding force(VBHF) can be used as one of the effective process parameters to reduce the springback amount with achieving better condition of formability. In this paper, VBHF with respect to the punch stroke is applied to the stamping process of the front side rear lower member for reducing the springback amount. From the analyses with constant blank holding force(CBHF), 24 kinds of VBHF conditions are utilized to investigate the springback tendency. It is noted that springback can be effectively reduced when BHF is increased near the bottom dead center because VBHF provides the tensile force to the blank with an adequate level of deformation without fracture.

• Transactions of Materials Processing
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• v.33 no.2
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• pp.103-111
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• 2024

With the increasing global interest in carbon neutrality, the automotive industry is also transitioning to the production of eco-friendly cars, specifically electric vehicles. In order to achieve comparable driving distances to internal combustion engine vehicles, the application of high-capacity battery packs has led to an increase in vehicle weight. To achieve light-weighting and durability requirements of automotive components simultaneously, there is a demand for research on the application of Ultra-High Strength Steel (UHSS). However, when manufacturing chassis components using UHSS, there are challenges related to fracture defects due to lower elongation compared to regular steel sheets, as well as spring-back issues caused by high tensile strength. In this study, a simulated specimen that is not affected by the property changes of four materials was designed to improve formability of the rear cross member, which is the most challenging automotive chassis component. The influence and correlation of material-specific variables were analyzed through finite element analysis (FEA) for each material with tensile strength of 440, 590, 780, and 980 MPa grades, resulting in the development of a predictive equation. To validate the equation, the simulated specimens of 980 MPa grade were produced from the test molds. Then the reliability of the FEA and predictive equation was verified with measured specimen data using a 3D scanner. The results of this study can be proposed to improve the formability of UHSS chassis components in future researches.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.774-777
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• 2001

This paper describes a research work of developing a computer-aided design system of cold forging products. An approach to the system is based on the knowledge-based rules. Knowledge for the system is formulated from plastic theories, experimental results and the empirical knowledge of field experts. The system has been written in AutoCAD with a personal computer and is composed of six modules, which are selection of billet material, input of final product, process planning design, preform modification, insert design, shrink rings design module. Based on knowledge-based rules, the system is designed by considering several factors such as volume constancy, limite of formability by material, preform shape and so on.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.75-76
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• 2008

In this study, texture development and bending characteristics of strong {0002} textured were observed. AZ31 Mg alloy sheets were prepared along the angle of 0 and 12.5 degrees to the lolling direction or {0002} texture. Prepared samples with different angles to the rolling direction were rolled at room temperature condition and after subsequent heat treatment to investigate texture with x-ray diffractometer, respectively The specimen having along the angles of 0 degree to rolling direction shows the highest load and 12.5 degrees specimen shows the highest displacement among any other specimens in bending test.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.114-117
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• 2008

Curved thick plate forming in shipbuilding industry is currently performed by a thermal process, called as Line Heating by using gas flame torches. It was examined as an alternative way in this study to manufacture curved thick plates by the multi-punch die forming. Experiments and finite element analyses were conducted to evaluate the feasibility of the reconfigurable discrete die forming to the thick plates. Configuration of the multi-punch dies suitable for multi-curvature was investigated. As a result, single step forming by reconfigurable discrete die with scale factor improved formability.