• 산업기술연구
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• 제30권A호
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• pp.49-57
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• 2010

A forming limit diagram (FLD) defines the extent to which specific sheet material can be deformed by drawing, stretching or any combination of those two. To determine the forming limit curve (FLC) accurately, it is necessary to perform the tests under well-organized conditions. In this study, the influence of several geometric or process parameters such as the blank shape and dimensions, strain measuring equipments, test termination time, forming speed and lubricants on the FLC is investigated.

• 소성∙가공
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• 제19권1호
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• pp.17-24
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• 2010

A stretch forming method has been widely used in sheet metal forming process. Especially, this process has been adopted in aircraft and high-speed train industries for skin structure forming having a variety of curvature. Until now, solid dies, which are designed with respect to the specific shapes and manufactured as a single piece, have been usually applied to stretch forming process. Therefore, a great number of solid dies has to be developed according to the shapes of the curved skin structure. Accordingly, a flexible die is proposed in this study. It replaces the conventional solid dies with a set of height adjustable punch array. A usefulness of the flexible die is verified through a formability comparison with the solid die using finite element method considering an elastic recovery and the stretch forming apparatus with the flexible die is developed.

• 소성∙가공
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• 제27권4호
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• pp.236-243
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• 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.

• 소성∙가공
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• 제21권6호
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• pp.360-365
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• 2012

The aim of this study was to investigate the effects of forming depth on the deformation behavior of cup-like tubes made of AISI1020 steel in tube spinning process. Spinning process was performed on cup-like tubes, which had an inner diameter of 34mm and thicknesses of 7, 8.5 or 11.5mm. The forming depths achieved were 3, 4, and 5.5mm. The complex deformation behaviors occurring during the tube spinning process was explained using the experimental results. Also analyzed were the causes of the material buildup and the bulge defect of inner surface, observed on cross section of tubes. The relationship between tube spinning conditions and the height of bulge defect was examined. The results indicate that bulge defect is increased with a decrease of the forming depth. Moreover, a critical forming depth exists for preventing the generation of the bulge defect in the tube spinning process. The present results will be useful for future decisions of forming depths for successful tube spinning of cup-like tubes.

• 소성∙가공
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• 제31권2호
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• pp.57-63
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• 2022

The current study performed formability analysis of a heat exchanger separator for an electric vehicle to apply a high-strength aluminum sheet based on parametric analysis. Mechanical properties for sheet metal forming simulation were evaluated by tensile test, bulge test, and Nakajima test. Two-stage crash forming was established by considering the mass production process using conventional low-strength aluminum sheets. In this study, FEM for the two-stage forming process was conducted to optimize the corner radius and height for improving the formability. In addition, the possibility of a one-stage forming process application was confirmed through FEM. The prototype of the sample was manufactured as FEM results to validate the parametric analysis. Finally, this result can provide a one-stage forming process design method using the high-strength aluminum sheet for weight reduction of a heat exchanger separator for an electric vehicle.

• 소성∙가공
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• 제13권4호
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• pp.342-349
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• 2004

The form-joining process (or clinching) uses a set of die and punch to impose the plastic deformation-induced geometric constraint on a sheet metal pair. The joining strength from the process ranges 50-70 percent of that of the resistance spot welding. In this paper, a new form-joining process with the aid of an adhesive is proposed in which an epoxy adhesive is applied to a sheet metal pair, and before it cures the pair is clinched to cause the geometric constraint in the form of a protrusion. In order to reduce the forming load and the height of protrusions, a new die and punch set with a very small clearance is devised to reduce the depth of drawing and the forming load. Taguchi method is employed to find the optimal values of design parameters. To implement each case of the orthogonal array, the finite element method is used. The experiments show that in the tensile-shear test, the bonding strength of the new form-joining process with an epoxy adhesive is approximately the same as that of the resistance spot welding; and in comparison with the other two form-joining processes with an epoxy adhesive, the height of protrusions is reduced by more than 65 percent and the forming load by 50 percent.

• 소성∙가공
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• 제4권1호
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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.

• 소성∙가공
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• 제11권1호
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• pp.54-60
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• 2002

The purpose of the present paper is to investigate the effect of Process parameters such as internal pressure, amount of axial feeding, and frictional condition between the die and the material on the tube hydro-formability. For carbon steel tubes(STKM 12A, STBH 410 and SPS 290), simple bulging, circular bulging and Tee-fitting tests are performed to evaluate the hydro-formability of these materials which is determined by deformation characteristics such as thickness distribution, forming height and branch dome shape. The formabilities obtained from these tests are analysed and compared with the results of the numerical simulation.

• 동력기계공학회지
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• 제15권6호
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• pp.53-58
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• 2011

To optimization of mlod for fineblanking forming of sector gear of recliner, it was analyzed the effect of clearance, V-ring height, V-ring position, blank holding force and counter punch force. In case of 0.003 mm of clearancs, the finest shear plane was obtained, but optimization between die and punch clearance was 0.005 mm. The height of V-ring was 0.7 mm. In case of increasing of hold force, the size of shear plane got better and the decrement of thickness became smaller. Both the size of shear plane and the decrement of thickness increased according to increasing of counter punch force.

• 소성∙가공
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• 제12권8호
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• pp.693-701
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• 2003

In this paper, the influence of frictional conditions on the backward impact extrusion of aluminum battery casing with large aspect ratio has been investigated. In the simulation, MSC.Superforge, a package based on the finite volume method, is used for the extrusion analysis. The formability and earing problem during the production have been evaluated by studying the sensitivity to frictional effects. During the sensitivity analysis, the friction factor was varied from 0.02 to 0.24. As the friction factor is increased, the forming height of the narrow edge is decreased, and the forming height of the wide edge is increased. When the friction factor becomes 0.2, the earing problem does not occur The experimental results show a good agreement with analytical results.