• Transactions of Materials Processing
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• v.10 no.3
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• pp.246-246
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• 2001

The conventional and new forming processes of a steel shell body are analyzed by the rigid-plastic finite element method. The conventional process contains five forming stages such as bending, drawing, ironing, heading and sizing, which was designed by a forming equipment expert. The results of simulation of the conventional forming process are summarized in terms of deformation patterns and load-stroke relationships for each forming operation. Based on the simulation results of the current five-stage, the shell body forming Process including backward extrusion is designed for improving the conventional process sequence. Forming loads of the proposed process are within the limit value, which is proposed by experts and the proposed process is found to be proper for manufacturing steel shell body.

• Transactions of Materials Processing
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• v.10 no.3
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• pp.245-252
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• 2001

The conventional and new forming processes of a steel shell body are analyzed by the rigid-plastic finite element method. The conventional process contains five forming stages such as bending, drawing, ironing, heading and sizing, which was designed by a forming equipment expert. The results of simulation of the conventional forming process are summarized in terms of deformation patterns and load-stroke relationships for each forming operation. Based on the simulation results of the current five-stage, the shell body forming Process including backward extrusion is designed for improving the conventional process sequence. Forming loads of the proposed process are within the limit value, which is proposed by experts and the proposed process is found to be proper for manufacturing steel shell body.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.152-158
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• 2006

The AutoForm previously used the membrane element and it accomplished sheet metal forming analysis. The membrane analysis has been widely applied to various sheet metal forming processes because of its time effectiveness. However, it is well-known that the membrane analysis can not provide correct information for the processes which have considerable bending effects. In this research experimental results were compared with the analysis results obtained by using the shell element which is applied newly in the AutoForm commercial software. The shell element is a compromise element between continuum element and membrane element. The Finite element method by using shell element is the most efficient numerical method. From this research, it is known that FEA by using shell element can predict accurately the problems happened in actual experimental auto-body panel.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.271-275
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• 2010

Forming tool design is carried out for a manufacturing a outer shell structure of the nozzle extension of regenerative cooling thrust chamber. The method which manufactures outer shell structure of nozzle extension is a metal forming process using thin plate. Because the configuration of outer shell structure is changed after forming process by springback effect, the outer shell structure can't be exactly formed with the same forming tool as configuration of the nozzle extension. Therefore forming tool design considering springback effect is necessary for manufacturing the outer shell structure of the nozzle extension. In this study, new designed forming tool configuration was generated to decrease the errors between nozzle contour and formed structure. The analysis results show that the errors between nozzle contour and formed structure is significantly decreased using the new designed forming tool.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.371-379
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• 1993

The wrinkling in the electromagnetic tube compression with a mandrel is remarkably smaller than that of the process without it. To analyze this phenomenon, the critical forming parameters such as the ratio of the clearance to the shell radius, the ratio of the thickness to the shell radius, and the ratio of the applied pressure to the standard pressure are introduced tp consider the effect of the mandrel, in addition to those of the thickness of shell and applied loads. The amplification ratio is also used to observe the magnitude of amplification. The results obtained by 2-D finite element method show that the initial imperfection embedded in the radius of cylindrical shell is the dominant factor to determine the final shape of the tube compression, and that the amplification ratio tends to have smaller values with the smaller clearance ratio and also with the larger thickness and pressure ratios.

• Transactions of Materials Processing
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• v.12 no.1
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• pp.49-59
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• 2003

To reduce the cost of finite element analyses for sheet forming, a 3D hybrid membrane/shell method has been developed to study the springback of anisotropic sheet metals. In the hybrid method, the bending strains and stresses were analytically calculated as post-processing, using incremental shapes of the sheet obtained previously from the membrane finite element analysis. To calculate springback, a shell finite element model was used to unload the final shape of the sheet obtained from the membrane code and the stresses and strains that were calculated analytically. For verification, the hybrid method was applied to predict the springback of a 2036-T4 aluminum square blank formed into a cylindrical cup. The springback predictions obtained with the hybrid method was in good agreement with results obtained using a full shell model to simulate both loading and unloading and the experimentally measured data. The CPU time saving with the hybrid method, over the full shell model, was 75% for the punch stretching problem.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.481-484
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• 2005

The AutoForm previously used the membrane element and it accomplished sheet metal forming analysis. The membrane analysis has been widely applied to various sheet metal forming processes because of its time effectiveness. However, it's well known that the membrane analysis can not provide correct information for the processes which have considerable bending effects. In this research it tried to compare the analysis results which use the shell element which is applied newly in the AutoForm commercial software with actual experimental results. The shell element is compromise element between continuum element and membrane element. The Finite element method by using shell element is the most efficient numerical method. From this research, it is known that FEA by using shell element can predict accurately the problems happened in actual experimental auto-body panel.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.97-98
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• 2007

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.62-65
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• 1999

To reduce the cost of finite element analyses for sheet forming a 3D hybrid membrance/sheel method has been developed to study the springback of anisotropic sheet metals. in the hybrid method the bending strains and stresses were analytically calculated as post-processing using incremental shapes of the sheet obtained previously from the membrane finite element analysis. To calculate springback a shell finite element model was used to unload the final shape of the sheet obtained from the membran code and the stresses and strains that were calculated analytically. For verification the hybrid method was applied to predict the springback of a 2036-T4 aluminum square blank formed into a cylindrical cup. the springback predictions obtained with the hybrid method was in good agreement with results obtained using a full shell model to simulateboth loading an unloading and the experimentally measured data. The CPU time saving with the hybrid method over the full shell model was 75% for the punch stretching problem.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.428-432
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• 2010

A study on the forming characteristics of outer shell structure for thrust chamber nozzle extension has been performed. In order to identify anisotropy of cold rolled sheet metal, three types of tensile specimens according to the direction to the sheet rolling axis were prepared and tested, and Landford's values were obtained using the results and applied to structural analysis. Forming characteristics of the outer shell structure of the nozzle extension are investigated through manufacturing and forming of the full scale outer shell structures, and strain values obtained by the forming processes are compared to the numerical analysis results. The results obtained by this study will be utilized to design forming tools and processes for manufacturing other outer shell structures which have a bigger expansion area ratio.