• Tribology and Lubricants
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• v.13 no.3
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• pp.48-55
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• 1997

The ball bearing with thin-section raceways which is much lighter than other conventional bearings used in most modem passenger cars and small tracks. The important design parameters of this bearing is the groove radius of raceways, the diametral clearance, the free contact angle and so on. The optimal value of these parameters were determined by considering the dynamic load capacity, the contact angle and the calculated fatigue life. The contact angle between a ball and raceways was calculated by considering the local contact deformation and the structural deformation of thin-section raceways which was estimated by FEM. The raceways were made by means of the press-forming process. The fatigue life tester was designed and manufactured. The fatigue life test was executed and the reliability of this bearing was confirmed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.302-305
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• 2007

The springback characteristics of AZ31B magnesium alloy sheet was investigated in OSU draw/bend test. Springback is the elastically-driven change of shape of a part after forming and it should be estimated and controlled to manufacture more precise products in sheet forming. The demands are increasing for magnesium alloy sheet press forming, but the study on its springback characteristics is insufficient. Strip draw/bend tests were conducted with various conditions - die radius, sheet thickness and controlled tensile force. The springback angles were measured from 'sidewall curl' of deformed shape. The tendency of springback angle was observed from the tests.

• Journal of Korea Multimedia Society
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• v.17 no.9
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• pp.1092-1097
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• 2014

It is difficult to perform automatic formation flight of UAV (Unmanned Aerial vehicle) when GPS (Global Positionig System) is out of order or has a system error, since the relative position estimation in the flight group is impossible in that case. In this paper, we design a relative localization system for the automatic formation flight of UAV. For this purpose, we adopt digital beam forming (DBF) to estimate the angle with the central controller of the flight group and Particle Filtering scheme to compensate the estimation error of ToA (time of arrival) method. Computer simulation results present a proper distance between the central controller and a following unit to maintain the automatic formation flight.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.3
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• pp.249-256
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• 1983

The study is concerned with the analysis of sheet metal for the prediction of limit drawing ratio and forming load. The direct redrawing process is analyzed by using an equilibrium approach and strain increment theory both for non-workhardening material and for workhardening material. Computations are carried out numerically for the workhardening case. Limit drawing ratios are predicted for some chosen variables. The forming loads are also computed with respect to punch travel. Then the predicted loads are compared with the experimental results. For ordinary lubricated conditions, the comparison shows reasonable agreement between the theory and experimental observation. It is also shown that limit drawing ration can be increased by using a greater die angle and proper lubrication significantly reduces the punch load. Finally numerical results show that material of greater R-value and strain-hardening exponent(n)is better for direst redrawing of sheet metal.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.513-517
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• 1997

Glass fiber reinforced thermoplastic composite materials have considerable promise for increased use in low cost high volum applications because of the potential for processing by solid phase forming. However, the forming characteristics of these materials have not been well known. The primary focus of this research is the investigation of the bendability of these composites and spring-back phenomena in pure bending. The materials tested contained 10, 35, and 40 percent by weight of randomly oriented glass fiber in a polypropylene matrix. The bending tests were performed at temperatures ranging form 75 ".deg. c" to 150 ".deg. c" and at punch speeds of 2.54 mm/sec and 0.0254 mm/sec. The measured bendability and spring back angle in pure bending werw compared with the predictions based on the simple analyical models. Goog agreement between experimental and analytical results was observed.esults was observed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.837-841
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• 2000

Spinning process is a chipless metal forming method for axi-symmetric parts, which is more economical, efficient and versatile method of producing parts than the other sheet metal forming process such as stamping or deep drawing. It is a point deformation process where a metal disc. cylinderical workpiece. or preform in contact with a rotating chuck is plastically deformed by axial or axial-radial Motions of a tool or roller. in this study the variation of spring back with respect to various forming roller corner radius(Rr) and angle of roller holder($\alpha$) is investigated. Good as a result will help to get more precise shape by control of spring back.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.663-666
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• 2002

Originally, the thermoforming method has been developed to produce the plastic parts which have simple geometric characteristics such as door trims and wrapping materials within the short time. But the thermoformed parts have non-uniform thickness distributions over the surface according to the material characteristics, set-up angle and geometry of the parts. But, only few analysis methods have been developed so far, due to the difficulties of the selection of important factors, and contribution of each factor in the simulation. So, to guarantee the dimensional accuracy and mechanical properties of crucial points in the thermoformed parts, it is necessary to develop the thickness prediction method. This research suggests a new approaching methodology to predict the thermoformed parts by modulating the control points of the NURBS curve. The newly developed method makes it possible not only to choose the suitable thickness of polymer sheets but also to induce data modification for vacuum forming.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.261-264
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• 2000

The objective of this work was to characterize mechanical properties of thermoplastic composites for various forming condition in compression molding. Randomly oriented long glass fiber reinforced polypropylene(PP) was used in the work. The composite materials contained 20%, 30%, and 40% glass fiber by weight. Compression molding was conducted to make the test specimen. Dimensional stability was measured on each forming condition with the spring-forward angle. Tensile test was conducted to characterize mechanical properties of formed parts in various forming conditions.

• Transactions of Materials Processing
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• v.19 no.2
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• pp.113-119
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• 2010

Hydroforming is the technology that utilizes hydraulic pressure to form tube or sheet materials into desired shapes inside die cavities. Tube hydroforming provides a number of advantages over the conventional stamping process, including fewer secondary operations, weight reduction, assembly simplification, adaptability to forming of complex structural components and improved structural strength. In many case, hydroformed parts have to be structurally joined at some point. Therefore it is useful if the hydroformed automotive parts can be given a localized attachment flange. In this study for the numerical process design FE analysis was performed with DYNAFORM 5.5. Die parting angle and circumferential expansion ratio was optimized. With optimized condition, bulge and hydroforming experiments to form flange were performed. Forming characteristic at various pressure conditions was analyzed and optimized internal pressure condition was evaluated. The results show that flanged parts can be successfully produced by tube hydroforming process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.465-468
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• 2008

In this paper, ABAQUS, one of the implicit finite element codes, is used to analyze the U-channel Draw benchmark problem of NUMISHEET 2005. Forming and springback stages have been done consecutively to compare their results with the experimental ones. The main measures for comparing are the side wall curl and angle. The result by numerical analysis are shown generally to be correspondent with the experimental results that the max. error is confined under about 10%.