• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.178-188
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• 2003

The wear of steam generator tubes is due to the vibration occurred between tubes and tube supporters. To predict the future wear depth, the wear constants of the impact and the sliding model is used. The wear constants, 3C/2 and K/3H, are found inversely from known wear depth and time. Using these constants, the future wear depths are found from two bodies that deform the elliptical shape. The results are compared with the measured wear depth of steam generator tubes in a nuclear power plant. The results show that the predicted wear depth envelopes the measured wear depth.

• 한국기계가공학회지
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• 제3권1호
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• pp.52-58
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• 2004

The material used is a commercial magnesium based alloy AZ31(Mg-3Al-1Zn)sheet with a thickness of 1.0mm. Uniaxial tension tests at warm temperature were carried out to investigate the material characteristics of K, m, and n. A warm drawing process with a local heating and cooling technique was developed to improve formability in this study with results of uniaxial tension tests because it is very difficult for Mg alloy to deform at room temperature by the conventional method. The die and blank holder were heated up, while the punch was water-cooled during deformation. FE simulations considering heat transfer were executed with Mg alloy to investigate the Improvement of deep drawability. For the assessment of improvement those were compare with the results of no considering heat transfer and room temperature.

• 한국기계가공학회지
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• 제10권5호
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• pp.58-64
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• 2011

In this paper, research on the manufacturing technology of hexagonal structure core is investigated. Also the optimal forming process of the honeycomb core is developed and the rolling process is analyzed using finite element code, $DEFORM^{TM}$-3D. The standard honeycomb has a uniform hexagonal structure defined by the material, cell size, cell wall thickness and bulk density. Honeycomb core products can be made from any thin, flat material. The most common cell configuration is the hexagon but there are many other shapes for special applications. Because of the precision shape and the thin thickness, the honeycomb core is not easy to manufacture in the metal forming process. Through this study it was confirmed that after the rolling process, the section of honeycomb close to the standard shape can be obtained. This result is reflected to the manufacturing process design for the honeycomb core.

• 한국기계가공학회지
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• 제19권8호
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• pp.22-27
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• 2020

Ring rolling is a type of forging for manufacturing large-diameter rings. Products manufactured by ring rolling are useful in the aerospace industry because of their excellent mechanical properties and high dimensional accuracy. The major components of the ring rolling process are a mandrel and main roll that shape the inside and outside of the ring, an axial roll that shapes the top and bottom of the ring, and a side rolls to position the ring. In this study, a simulation of ring rolling using finite element method (FEM) was performed. DEFORM, a commercial machining analysis program, was used. Based on the simulations, the mandrel feed force required for machining and the drive torque of the main roll were predicted. It was also possible to identify the metal flow caused by machining.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.339-343
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• 2000

Rapid prototyping for welding and milling is a hybrid approach that makes use of welding as additive and conventional milling as subtractive technique. For two years this concept has been used to verify manufacturing mold and mechanical parts successfully. In latest new fabrication methods. For example, manufacturing mold for two sort of materials and shell fabrication, have been applied to the concept in KIST. This methods will be an alternative proposal in rapid prototyping. Metal deposition for welding causes the part to deform. It is a handicap in our proceeding. To overcome this problem, in this paper, we represent an optimal welding path for FEM analysis. Eight paths are tried to this and the value of deformation is average and standard deviation in four points'. Then we can compare with eight cases and select the optimal path.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.385-388
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• 2000

During the deep drawing process an initially flat blank is clamped between the die and the blank holder after which the punch moves down to deform the clamped blank into the desired shape. In general, sheet metal forming may involve stretching, drawing, bending or various combinations of those basic modes of deformation. The deformation problems of sheet metal working involve non-linearity in geometry and material. In this work, The punch load and thickness strain of electro-galvanized sheet steel (SECD) for elliptical deep drawing are examined under the various process conditions including, punch shape radius, die shape radius. The changes of punch load and thickness strain distribution of the deformed elliptical cup are affected by the size of each die shape radius.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.523-526
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• 1997

Sheanng is one of the most important operating processes in the field of sheet metal manufacturing. Compared with casting, forging and machining, shearing is very economical to obtain the desired shape. In recent years there has been increasing the use of shearing process in the manufacturing of small and light electronic components. In this paper, it has been researched the experimental investigation to examine the mfl uence of shearing process parameters such as clearance and lower holder configuration. Through the experiment results, the more narrow clearance gives the smaller burr height and the removal of lower holder makes the worse sheared surface. And FE simulation of shearing process using DEFORM-2D were camed out and the results compared w~th experimental studies

• 한국정밀공학회지
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• 제22권8호
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• pp.100-107
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• 2005

The objective of the study is to improve the quality of wheel bearing hub by the rigid-plastic finite element analysis and the response surface methodology. The rigid-plastic finite element codes, AFDEX-2D and DEFORM-3D, were used to analyze the two-dimensional and three-dimensional forging processes, respectively. The response surface analysis is used to find the minimum underfill by the variation of design variables such as the height of billet after upsetting and punch angles of blocker dies. The metal flow of forged product shows good agreement with the results from 2D and 3D analysis. Also, the quality of the wheel bearing hub has been improved by the optimization of design variables and the machining time has been reduced by the machining allowance.

• International Journal of Precision Engineering and Manufacturing
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• 제3권3호
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• pp.21-27
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• 2002

In this paper, a simple test rig of high-speed crash for the front members of vehicles was developed for the improvement of crashworthiness of vehicle's side rail. The cart hanging the specimen is accelerated up to 35 mph by the traction wire and by the force of freely dropping weight and 1:3 accelerating pulleys. The cart with shock absorbers travels on the rail roads, so it does not transfer any additional vibration to the specimen. In order to measure the energy absorbed by the specimen when it collapse to the wall and during it deform, the two strain gage type load cells are used at the wall place. The test rig rated good to test the specimen like a side rail of vehicle as developing the vehicle's structures in the early design stage.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.244-249
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• 1997

Internal and external heat sources will cause to deform to machine elements in the contact joint of structure,which results in the change of contact pressure distribution different from initial assembly. Heat induced variations of contact pressure will change the static and dynamic properties such as contact stiffness,damping as well as contact heat conduction in the structure. In order to design and control the intelligent machine tool operating in variant conditions more sophisticatedly, the good prediction for the changes of prescribed propeties are strongly required especially in the contact elements adjacent to the rotational or linear bearing This paper presents some computational and experimental results in regard to static and dynamic characteristics of the press-fitted bush and shaft assembly which is a model of the bearing innerrace and shaft assembly. In the condition of heat generation on the outer surface of the bush,the effects of changes in the negative clearance and the heat flux on pressure distribution and dynamic properties are investigated. Results of this study show that the edge effect of the bush and the initial clearance have effects on the transient dynamic characteristics significantiy.