• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.8
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• pp.1276-1290
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• 1997

The previous elastic stiffness formulas of leaf type holddown spring assemblies(HDSs) have been corrected and extended to be able to consider the point of taper runout for the TT-HDS and all the strain energies for both the TT-HDS and the TW-HDS based on Euler beam theory and Castigliano'stheorem. The elastic stiffness sensitivity of the leaf type holddown spring assemblies was analyzed using the derived elastic stiffness formulas and their gradient vectors obtained from the mid-point formula. As a result of the sensitivity analysis, the elastic stiffness sensitivity at each design variable is quantified and design variables having remarkable sensitivity are identified. Among the design variables, leaf thickness is identified as that of having the most remarkable sensitivity of the elastic stiffness. In addition, it was found that the sensitivity of the leaf type HDS's elastic stiffness is exponentially correlated to the leaf thickness.

• Transactions of Materials Processing
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• v.19 no.8
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• pp.508-516
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• 2010

Thickening process in sheet metal forming is being increased to improve the strength as well as to reduce manufacturing process such as welding. This process can make it possible to obtain part locally thicker than that of initial sheet thickness. In this study, design method for manufacturing the component which has double sinks with local thickened wall is proposed. Deep drawing and upsetting processes are applied in order to form double sinks and thicken its walls. Used material is SPHC440 with the thickness of 2.0mm and initial blank size is determined on the basis of the final product. Distance between the center of double sinks and first drawing ratio to avoid fracture are the most significant factors during deep drawing. FE-analysis is implemented in order to determine the appropriate values. Progressive die is designed based on the proposed method and FE-analysis. As a result of experiment, locally thickened component can be manufactured, which has double sinks with the thickness about 3mm at the corner and wall.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.4
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• pp.44-55
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• 2004

In order to meet the requirement for higher thickness accuracy in tandem cold rolling processes, it is strongly necessary to have good performance in control units. To meet this requirement, this paper suggested an output regulating control system with a roll-eccentricity estimator for each rolling stand of tandem cold mills. Considering entry thickness variation and roll eccentricity simultaneously as the major disturbances, a synthesis of multivariable control systems was presented based on H$\infty$ control theory, which could reflect the knowledge of input direction and spectrum of disturbance signals on design. Then, to effectively reject roll eccentricity, a weight function having some poles on the imaginary axis was introduced. This lead to a non-standard H$\infty$ control problem, and the design procedures for solving this problem were analytically presented. The effectiveness of the proposed control method was evaluated through computer simulations and compared to that of the conventional linear quardratic control and feedforward control methods for roll eccentricity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.1
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• pp.117-123
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• 2001

In present study a methodology has been developed and applied for the optimum design and performance evaluation of microchannel heat sinks. The optimum design parameters include channel number and fin thickness. For a trial model of 127mm in length, 52.5mm in width, 16mm in height and 2.5mm in base thickness, the optimum channel number and the fin thinckness have been determined to be of 194 and 0.08359mm, respectively in laminar flow region. Performance of the optimally designed microchannel heat sinks has been compared with those having 50% and 150% of the number of channels. The results showed that the 50% and 150% designs increased the pumping power by 200% and 150%, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.9
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• pp.733-739
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• 2008

The X-ring is a elastomer with X-shaped cross-section used as a mechanical seal or gasket. Such a X-ring was equipped in a groove and compressed between two or more parts, acts as a seal on the interface. This study aims to detect contact stress and deformed shape of a X-shaped ring shell under various compressive contact conditions. A contact stress analysis was carried out by finite element analysis. The effect of compression rates and thickness design variable was analyzed. X-ring kept up the double seal until a compression rate of 20%. The maximum stresses of the X-ring was occurred at the top and bottom corner. The maximum contact stress of X-ring was rapidly increased according with the compression rate. The X-rings with thickness design variable from 1.3 mm to 1.5 mm had comparative low stress levels.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.559-563
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• 2011

Drop impact reliability assessment of solder joints on the flip chip is one of the critical issues for micro system packaging. Our previous researches have been showing that new solder ball compositions of Sn-3.0Ag-0.5Cu has better mechanical reliability than Sn-1.0Ag-0.5Cu. In this paper, dynamic reliability analysis using Finite Element Analysis (FEA) is carried out to assess the factors affecting flip chip in drop simulation. The design parameters are size and thickness of chip, and size, pitch and array of solder ball with composition of Sn1.0Ag0.5Cu. The board systems by JEDEC standard including 15 chips, solder balls and PCB are modeled with various design parameter combinations, and through these simulations, maximum yield stress and strain at each chip are shown at the solder balls. It is found that larger chip size, smaller chip array, smaller ball diameter, larger pitch, and larger chip thickness have bad effect on maximum yield stress and strain at solder ball of each chip.

• Korean Institute of Interior Design Journal
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• v.16 no.5
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• pp.98-106
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• 2007

With the recent increase in the amount of interior materials, the medium-density fiberboard(MDF) has continued to be produced at an increasing rate. Accordingly, to prevent the deformation of MDF after its construction, secure the precision of its finishing and improve the performance of its design, this study attempted to investigate the effect of environment humidity conditions on flatness according to the field used in MDF and its relationship to other physical properties. An attempt was made to conduct this study by changing the conditions of surface treatment by moisture and by thickness. For this purpose, it is judged that it is desirable to prevent scheme to maintain the flatness by defining the coefficient of water absorption-induced length change as in the regulation on low-density soft fiberboard and adjusting the standard for wet bending strength upward. It is thought that is further studies will be conducted about the effect of material, adhesive and thermal pressure condition, production system and processing method used in MDF on its scheme to maintain the flatness and changes in length and thickness expansion.

• Journal of the Korean GEO-environmental Society
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• v.6 no.4
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• pp.13-26
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• 2005

In this study, research results on organic and inorganic pollutant migration through single and composite liner were summarized. On the basis of these summarized research results, a design program for landfill liner, which can be used to optimize the liner thickness based on the allowable ground water criteria around the landfill subsurface, was developed. A reasonable liner thickness was obtained from the program output results, in the case of the migration of $Cl^-$ ion through a single clay liner. Therefore, the developed program could be used to carry out a preliminary design for landfill liners with respect to organic and inorganic pollutants.

• Korean Journal of Computational Design and Engineering
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• v.7 no.3
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• pp.148-156
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• 2002

Most Rapid Prototyping (RP) processes adopt a solid Computer Aided Design (CAD) model, which will be sliced into thin layers of constant thickness in the building direction. Each cross-sectional layer is successively deposited and, simultaneously, bonded onto the previous layer; and eventually the stacked layers from a physical part of the model. A new RP process, the transfer-type Variable Lamination Manufacturing process using expandable polystyrene foam sheet (VLM-ST), has been developed to reduce building time and to improve the surface finish of parts with the thick layers and a sloping surface. This paper describes the generation of Unit Shape Layer (USL), the cutting path data of the linen. hotwire cutter for the VLM-ST process. USL is a three-dimensional layer with a thickness of more than 1 mm and a side slope, and it is the basic unit of cutting and building in the VLM-ST process. USL includes data such as layer thickness, positional coordinates, side angles of each layer, hotwire cutting speed, the heat input to the hotwire, and reference shape. The procedure of generating USL is as follows: (1)Generation of the mid-slice from the CAD model, (2)Conversion of the mid-slice into a simply connected domain, (3)Generation to the reference shape for the mid-slice, (4)Calculation of the rotation angle of the hotwire of the cutting system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7878-7884
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• 2015

Marine sea water pump with impeller using carbon fiber block was developed to prevent the impeller corrosion by the salinity. A numerical analysis was carried out in order to optimize the impeller and volute design for marine sea water pump and to investigate the sensitivity of the related parameters(impeller thickness, surface roughness) using CFD commercial code. The impeller thickness is limited because of the weight. Since the impeller using the carbon fiber lights, the thickness which has a maximum efficiency can be used. The results show that the surface roughness leads to an 7% reduction in pump efficiency.