• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.19-24
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• 1997

The weld line location and the weld line movement in stamping with laser-tailor welded blanks(TWB) were investigated through square cup deep drawing tests. The step blank holder was introduced to form TWB of different thicknesses without wrinkling, and the non-uniform blank holding force(BHF) was enforced to control weld line movement. Test results of the blanks with shifted weld lines showed that the large portion of the thinner area could result in a large weld line movement. Careful selection of the weld line location and the BHF control should be adapted in TWB design to avoid failures and to ensure its formability.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.93-99
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• 2005

In this work, computer-aided process design is carried out to develop an optimal preform of a pressure vessel. Knowledge-based rules are employed to design the preform, and they are formulated using the handbooks of plasticity theories. In the FE-analysis, a commercial finite element code, ABAQUS was employed. Axisymmetric deep drawing of a hemisphere-bottomed cup has been analyzed fur various combinations of die design parameters. The length of the land of die, the clearance between punch and die and the clearance between the blank holder and die are optimized to minimize the forming load. The results of the simulations are verified with the experiments which are scaled down to one tenth of the actual size.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.9
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• pp.793-798
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• 2015

This study investigates the effects of the size of copper sheets on the plastic deformation behavior in a microscale deep drawing process. Tensile tests are conducted on the copper sheets to study the flow stress of the materials with different grain sizes before carrying out the microscale deep drawing experiments. After the tensile tests, a novel desktop-sized microscale deep drawing system is used to perform the microscale deep drawing process. A series of microscale deep drawing experiments are subsequently performed, and the experimental results indicate that an increase in the grain size results in the reduction of the deformation load of the copper sheets due to the effects of the surface grain. The results also show that the blank holder gap improves both the formability of copper sheets and the material flow.

• Transactions of Materials Processing
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• v.32 no.4
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• pp.199-207
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• 2023

The stainless steel basket-bowl, a critical component of washing machines, is characterized by its unique two-tiered circular shape. This study explores the potential of a draw-bead free die design to address tearing concerns in the prospective plastic layer during the drawing operation. In order to prevent wrinkles that may arise from the absence of a draw-bead, a two-stage punch configuration is proposed. The influence of the blank holder force on wrinkle reduction is also examined. Finite element analysis is employed to evaluate the proposed die design by analyzing the wrinkle shape and strain mode. The results confirm that the stainless steel basket-bowl can be successfully drawn without wrinkles utilizing the proposed two-stage punch without a draw-bead on the blank holder. These findings contribute to the development of more efficient and reliable manufacturing processes for the stainless steel basket-bowl production.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.616-620
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• 2001

The wrinkling in the flange and wall of a part is a predominent failure mode in stamping of sheet metal parts. In many cases this wrinkling may be eliminated by appropriate control of the blank holding force(BHF), but BHF affects the draw depth. Although the wrinkles of flange have been made in the incipient stage of drawing, if the height of wrinkles is maintained under a prescribed limit by decrease or extinction of wrinkles in the course of drawing, small BHP can be allowed so that the depth of drawing could be increased. Authors research the variation of the wrinkles in flange in the course of square cup drawing by using aluminium A1015 and aluminium alloy A5052.

• Transactions of Materials Processing
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• v.15 no.5 s.86
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• pp.387-394
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• 2006

In order to see the effect of die deformation on the forming analysis of sheet metals, the draw-ins, strains, and spring-backs of an automotive fender panels are numerically simulated by considering the die deformation found by the simultaneous structural analysis of press and dies. By coupling the forming analysis and the structural analysis, the die deformation is simultaneously taken into account in the forming process. Furthermore, for the consideration of load difference transferred among the upper die, punch, and blank holder due to the changes in sheet thickness, the gap elements are employed instead of the blank sheet in the structural analysis. The numerical simulation results of an automotive finder draw panel are compared with the measurements. The comparison of the forming and spring-back analysis results between the rigid die and the deformed die shows that the consideration of tool deformation can predict more accurately the forming and spring-back of sheet metals.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.845-848
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• 2002

The wrinkling in the flange and wall of a part is a predominent failure mode in stamping of sheet metal parts. In many cases this wrinkling may be eliminated by appropriate control of the blank holding forco(BHF), but BHF affects the draw depth. Gotoh had studied the wrinkles under 0.02mm in height. In general, the height of wrinkles could be limited under 0.2mm practically. Therefore small BHP can be allowed so that the depth of drawing could be increased. Authors research the variation of the wrinkles in flange in the course of cup drawing by using aluminium alloy Al050 and A5052.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.217-219
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• 2008

A new experimental model for determining drawbead forces, which modifies the dieface of Nine's experimental model, is introduced and the better validity of the drawbead opening and restraining forces of new model than those of Nine's is demonstrated. While Nine's model considers a blank holding force as one of forming variables, new model excludes it by removing blank holder in the dieface. The comparison of the strains found by FEM simulation of automotive fender draw forming process with those measured in a formed panel recommends the new model for accurate drawbead forces.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.8
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• pp.182-192
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• 2001

During the deep drawing process an initially flat blank is clamped between the die and the blank holder after which the punch moves down to deform the clamped blank into the desired shape. In general, sheet metal forming may involve stretching, drawing, bending or various combinations of those basic modes of deformation. The deformation problems of sheet metal working involve non-linearity in geometry and material. In this work, The punch load and thickness strain of electro-galvanized sheet steel (SECD) for elliptical deep drawing are examined under the various process conditions including, punch shape radius, die shape radius. The changes of punch load and thickness strain distribution of the deformed elliptical cup are affected by the size of each die shape radius.

• Transactions of Materials Processing
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• v.17 no.7
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• pp.501-506
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• 2008

In this study, a forming magnesium alloy circular cup was simulated accounting for heat transfer at elevated temperatures. In order to predict the failure of magnesium alloy sheet during simulation, the forming limit diagram, which is used in sheet metal forming analysis to determine the criterion for failure, was investigated. For the failure prediction in the simulation accounting for heat transfer, the forming limit diagram for a temperature the same as the temperature of the blank element was used. The result of the simulation showed that the drawn depth increases with the increase of the die-holder temperature, and is in accord with the experimental results above the die-holder temperature of $150^{\circ}C$. The forming limit diagram provided a good guide for the failure prediction of warm forming simulation accounting for heat transfer. In addition, the effect of the tool shoulder radius on the drawn depth at various tool temperatures is verified using the simulation conditions which agreed with the experimental results.