• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.8
• /
• pp.82-91
• /
• 1997

The major objective of this study is to establish analytical technique in order to analyze the behaviour of semi-solid material considering induction heating of the billet. Induction heating process is analyzed by using commerical finite element software. ANSYS. The finite element program, SFAC2D, for the simulation of deformation in semi-solid state is developed in the present study. The semi-solid behaviour is described by a viscoplastic model for the solid phase, and by the Darcy's law for the liquid flow. Simple compression and closed-die compression process considering induction heating are analyzed, and also it is found that the distribution of initial solid fraction of the billet has an important effect on deformation behaviour of semi-solid material. In order to verify the effectiveness of proposed analytical technique the simulation result is compared with experimental result.

• Proceedings of the Korean Society of Rheology Conference
• /
• 2000.11a
• /
• pp.91-94
• /
• 2000

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2008.06a
• /
• pp.579-580
• /
• 2008

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2005.11a
• /
• pp.28-29
• /
• 2005

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.22 no.2
• /
• pp.302-310
• /
• 1998

In the accompanying paper, part I, we have presented the physical modeling and the associated numerical analysis of injection molding process with a compressible viscoelastic fluid model. In part II, the effects of compression stage in the injection/compression molding process are presented. Numerical results showed that the injection/compression molding process reduced birefringence as compared with the injection molding process. In this respect, one can conclude that the injection/compression molding process is more suitable for manufacturing the precise optical products than the injection molding process. In the distribution of birefringence, the effect of packing procedure in injection/compression molding process was found to be similar to that in injection molding process. From the numerical results, we found that birefringence becomes smaller as the melt temperature gets higher and the closing velocity of the mold gets smaller with the flow rate and the mold temperature affecting the birefringence insignificantly. As far as the distribution of density is concerned, the flow rate, the melt temperature, and the closing velocity of the mold had insignificant effect on the distribution of density in comparison with the mold temperature.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.15 no.1
• /
• pp.27-33
• /
• 2005

In this study, the process parameters in ceramics powder compaction are optimized for getting high relative densities of ceramic products. To find optimized parameters, the analytic models of powder compaction are firstly prepared by 2-dimensional rod arrays with random green densities using a quasi-random multiparticle array. Then, using finite element method, the changes in relative densities are analyzed by varying the size of Al₂O₃ particle, the amplitude of cyclic compaction, and the coefficient of friction, which influence the relative density in cyclic compactions. After the analytic function of relative density associated process parameters are formulated by aid of the response surface method, the optimal conditions in powder compaction process are found by the grid search method. When the particle size of Al₂O₃ is 22.5 ㎛, the optimal parameters for the amplitude of cyclic compaction and the coefficient of friction are 75 MPa and 0.1103, respectively. The maximum relative density is 0.9390.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.10
• /
• pp.887-894
• /
• 2016

The CNG pressure vessel is manufactured by a deep drawing and ironing (D.D.I) process for forming cylinder parts, followed by a spinning process for formation of the dome part. However, studies on the buckling phenomenon of the dome part and formation of the inlet part have not been performed yet, and the CNG pressure vessel is produced by the experience of the field engineers and the trial and error method. In this study, buckling phenomenon during the spinning process was predicted by comparing critical buckling loads obtained through theoretical analysis with axial loads from the FEA, and a method for preventing buckling of the dome part was proposed by employing commercial software (Forge NxT 1.0.2). Also, to form the inlet part, forming loads of the roller at contact point between the roller and the dome part were analyzed according to radii of the dome part, and the inlet part was formed by controlling the radius of the dome part.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2002.05a
• /
• pp.184-187
• /
• 2002

Compression molding was specifically developed for replacement of metal components with composites. As the mechanical properties of the products are dependent on the separation and orientation, it is important to research the fiber mat structure and molding conditions. In this study, the effects of the fiber mat structure(NP: 5, 10, 25punches/$\textrm{cm}^2$) and the mold closure speed($\dot{\textrm{h}}$=0.1, 1, 10mm/min) on the viscosity of composites were discussed. The composites is treated as a Non-Newtonian power-law fluid. The parallel-plate plastometer is used and the viscosity is obtained from the relationship between the compression load and the thickness of the specimen.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2001.10a
• /
• pp.29-32
• /
• 2001

The objective of this work was to optimize processing parameters of hybrid thermoplastic composites in compression molding. The mechanical properties of the composites manufactured with various forming conditions were measured to characterize processing parameters. Polypropylene(PP) composites containing randomly oriented long carbon fiber and carbon black were used in this work. The composite materials contained 5%, 10%, 15%, and 20% carbon fiber and 5%, 10%, 15%, 20%, and 25% carbon black by weight. Compression molding was conducted at various mold temperatures. The temperature of the material in the mid-plain was monitored during the forming. Crystallinity was also measured by using XRD. The tensile modulus of the composites increase, with increasing the mold temperature. However, the impact strength of the composites decreases as mold temperature increases.

• Proceedings of the KSME Conference
• /
• 2001.06c
• /
• pp.438-444
• /
• 2001

The objective of this study is to provide a simple methodology to find optimum processing conditions to fabricate sub-micron structured DVD-RAM substrates with superb optical and geometrical properties. It was found that the birefringence, which is regarded as one of the most important optical properties for an optical disk, was very sensitive to the mold wall temperature history. Also, the integrity of the replication, represented by the land-groove structure and the radial tilt were influenced by the mold temperature and the compression pressure. A set of optimum conditions were obtained by applying Design of Experiment and the objective functions composed of three different objectives.