• Fibers and Polymers
• /
• v.2 no.1
• /
• pp.140-143
• /
• 2001

To better understand the formation of necking in drawing processes of fibers, strain distributions during drawing processes have been analyzed. For simplicity, one-dimensional incompressible steady flow at a constant temperature was assumed and quasi-static model was used. To describe mechanical properties of solid polymers, non-linear visco-plastic material properties were assumed using the power law type hardening and rate-sensitive equation. The effects of various parameters on the neck formation were matematically analyzed. As material property parameters, strain-hardening parameter, visco-elastic coefficient and strain-rate sensitivity were considered and, for process parameters, the drawing ratio and the process length were considered. It was found that rate-insensitive materials do not reach a steady flow state and the rate-sensitivity plays a key role to have a steady flow. Also, the neck formation is mainly affected by material properties, especially for the quasi-static model. If the process length changes, the strain distribution was found to be proportionally re-distributed along the process line by the factor of the total length change.

• Design & Manufacturing
• /
• v.10 no.1
• /
• pp.31-35
• /
• 2016

In sheet metal forming process, drawing is typical process. And the key factor of drawing is blank holding force (BHF) A low BHF can cause wrinkling, whereas a high BHF can cause fracture during a deep drawing process. Thus, formability can be influenced by application appropriate BHF. In this study, a variable blank holding force (VBHF) is applied to extend the forming limit by avoiding both wrinkling and fracture. To determine VBHF in drawing process, numerical simulations and statistical analysis are carried out using commercial FEM software.

• Transactions of Materials Processing
• /
• v.5 no.1
• /
• pp.27-36
• /
• 1996

In this paper a computer-aided design system for axisymmetric deep drawing process will be described. An approach to the system is based on the knowledge based system. The system has been written in AutoLISP with personal computer. The system is composed of four main modules such as input geometrical design test & rectification and user modification. the system which aids designer provides powerful capabilities for the design of axisymmetric deep drawing process.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.12
• /
• pp.2936-2948
• /
• 1993

Multi-stage deep drawing is an important sheet metal forming process. The deformation mechanisms of sheet metals during forming processes are complicated mainly due to the geometry and the lubrication of tools involved, the formability and the anisotropic behaviour of the material. The multi-stage deep-drawing processes including normal-drawing, reverse-drawing, and re-drawing are analyzed by use of the rigid-plastic finite element method. The anisotropic behaviour represented by r-value can be incorporated into the formulation. Punch/die loads and thickness distributions were obtained as results of simulating axisymmetric deep drawing processes. The computed results showed good agreements with experiments.

• Journal of the Korean Society for Precision Engineering
• /
• v.10 no.3
• /
• pp.198-204
• /
• 1993

The study is concerned with finite element analysis and design of axisymmetric deep drawing by local heating. When the bottom shape of a cup is not flat but in complex-shaped, i.e., hemispherical, the cup cannot be drawn in one or two processes in the conventional deep drawing process and the limit drawing ratio is limited as well. By introducing local heating selectively with regards to the heating position, the formability of the sheet metal can be greatly increased with the reduced number of processes. In the Process analysisthe rigid- viscoplastic finite element method is employed and the temperature effect is incorporated. Bishop's step-wise decoupled method is employed to analyze the thermomechanical interaction between deformation and heat transfer. Axisymmetric deep drawing of a hemisphere-bottomed cup has been analyzed for various combinations of heat application in the punch and the die. At the first stage of deep drawing stretch forming is practically carried out by firmly pressing the blankholder with the punch and the die heated at various levels of temperature. Then at the second stage the same cup is drawn for the saame or different combination of temperature. From the computation, it has thus been shown that the fromability of a cup is greatly increased in two-stage deep drawing with increased limet drawing ratio.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1994.06a
• /
• pp.191-198
• /
• 1994

A practical example of the axisymmetric deep drawing process is simulated by the elastic-plastic finite element analysis using updated Lagrangian approach considering the large deformation. An approach is suggested to solve the problem of the ductile fracture that may encounter during the deep drawing process. The result can be applied to the design of the die for the axisymmetric deep drawing.

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.11
• /
• pp.46-57
• /
• 1998

Even though there are some studies on the deep drawing process and process planning, little study has been done on the methodology of process planning of secondary operations of deep drawing such as 'piercins'. In this paper, first, we systematized the methodology of the process planning of secondary operations on axisymmetric cup. Second we described the development of the expert system for their CAPP For these studies, we extracted the knowledge of their process planning from experts and analysed and systemized them. To develop the expert system, rule-based reasoning paradigm is used. The shape information of manufacturing features of secondary operations are manually input to the system through SUI. The process planning results are automatically connected to AutoCAD. We believe that the systematized process knowledge and the development of the expert system for its CAPP could give lots of aids to the associated field.

• Textile Coloration and Finishing
• /
• v.28 no.4
• /
• pp.253-270
• /
• 2016

In the wool textile industry, the necessity for technology development has been steadily raised to create improved fineness and yarn count of existing wool yarns with thick fineness for ensuring higher quality grades of wool yarn. Recently, through controlling fineness of wool yarn for making finer wool in relation with environmentally-friendly and high-sensitivity trend, a differentiated continuous drawing process where the quality of wool can be artificially manipulated has been suggested in the latest textile industry. This study investigated the basic conditions during the continuous drawing process which enable to manufacture wool yarn with fine count by controlling reducing agent treatment, physical drawing and drying after reducing agent treatment, and oxidizing agent post-treatment conditions. Furthermore, this study reviewed the drawing effects by applying the basic conditions for reduction and oxidation reaction in the drawing processes of wool/cashmere, wool/silk, wool/polyester blended yarns as well as such wool yarns. Also, in order to review the practicability, this study examined the physical properties and dyeability of drawn wool yarn applied textile materials in comparison with normal wool yarn applied textile materials.

• Transactions of Materials Processing
• /
• v.8 no.4
• /
• pp.356-363
• /
• 1999

This paper discusses some techniques for the determination of optimum blank size and pre-form design for multi-stepped deep drawing of oval shell. The deep drawing process of oval shape has been regarded as more difficult than that of cylindrical shell because of its complicated behavior of plastic deformation. But there is insufficient information in this area to carry out successful deep drawing work of irregular products such as oval, rectangular, and square shapes. In order to find the optimum conditions, the drawing apparatus for two kinds of pre-form design are built, a series of drawing experiments performed, and thickness stain distributions measured. From the results of thess suggested experiments, various optimum process variables are observed and discussed.

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.12
• /
• pp.68-71
• /
• 1998

Rectangular deep drawing process is widely used in sheet metal forming. But there are various defects such as earring, wrinkling, tearing, etc. In order to avoid the defects, an optimum blank shape is required. But it has not been generalized to determine the optimum blank shape because deep drawing processes are involved in complex process parameters. So, it is very necessary to do research systematically about determining the optimum blank shape of deep drawing process. In this study a rectangular cup drawing test has been carried out to determine the optimum blank shape for various stainless steel sheets. From the test, a new blank model, which has no earring, is proposed.