• Transactions of Materials Processing
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• v.9 no.4
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• pp.339-347
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• 2000

For the successful forming of tailored blank, it is important to control the deformation of the stretch flange mode, which is strong1y dependent upon the location of weld line and blank shape. In order to investigate the effects of tailored blank design factors on the stretch flange forming, we made the model die which can simulate stretch flange mode. Taguchi method was employed to analyze the sensitivity of blank design factors for the forming of tailored blank. From the results of experiment S/N ratios were calculated and using Variance Analysis, significance of parameters and optimal condition of each factors were extracted. Based on these analyses, the weld line height and the strength ratio and the arc center height were selected as effective parameter. The analysed result was practically applied for Side outer panel stamping process.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.3
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• pp.220-226
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• 1994

In this paper the failure mechanisms of polypropylene resin composites filled with calcium carbonate particulates have been studied in the temperature range $-50^{\circ}C$ to $-50^{\circ}C$ The fillers used are both untreated and surface treated with stearic acid. The impact fracture toughness is evaluated from the impact energy absorbed divided by the uncut ligament area of the specimen. Impact fracture toughness increases as temperature is raised whether the fillers are coated or not. The static fracture toughness of these particular composites is evaluated based on the linear clastic fracture toughness of these particular composites is evaluated based on the linear clastic fracture mechanics. Static fracture toughess decreases with increasing temperature whether the fillers are coated or not. An extended stress whitened zone are observed through a large number of availabel sites for cavitation/debonding along particle matrix interface and matrix deformation.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.15 no.2
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• pp.185-193
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• 1997

While close range photogrammetry has been widely applied for static deformation analysis, video cameras have many characteristics that make them the sensors of choice for dynamic analysis of rapidly changing situations. They also have limitations. The aim of this research is to explore the potential of a video system for monitoring dynamic objects. A pilot system consists of two camcorders, VCR, and PC with frame grabber. To estimte the performance of this system for moving objects, a car was imaged covering several phases when starting to drive. The sequential images of a moving car were recorded on VCR. 15 images per second were digitized in an off-line mode by frame grabber. The image coordinates of targets attached to the rear bumper of a car were acquired by IDRISI, and the object coordinates were derived based on DLT. This research suggests that home video cameras, PC, and photogrammetric principles are promising tools for monitoring of the moving objects and vibrations as well as other time dependent situations.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.11b
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• pp.245-252
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• 2005

An underground research facility (KURF) is under construction at KAERI for the in situ studies related to the validation of a HLW disposal system. For the safe construction and long-term researches at KURF, mechanical stability of the facility should be evaluated. In this study, 3D mechanical stability analysis using the rock mass properties determined from various in situ as well as laboratory tests was carried out. From the analysis, it was possible to predict the rock deformation, stress concentration, and plastic zone developed before and after the excavation. A test blasting was performed to characterize the site dependent dynamic response, which can be used for the prediction of the blasting impact on the facilities in KAERI.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.133-133
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• 2004

박막이나 초미세 구조체의 경도 및 탄성계수 측정을 위한 나노 압입실험에서는 Oliver ＆ Pharr가 제안한 하중-변위 측정 나노압입법이 널리 쓰이고 있다 위 실험법에서, 나노경도(nano-hardness; H$_{n}$)는 최대하중을 계산된 접촉면적 (A$_{c}$)으로 나누어 평가하고, 압입자 및 박막의 탄성성질을 포함하는 환산 탄성계수 (reduced modulus ; E$_{r}$)는 하중제거곡선의 초기 기울기인 접촉탄성강성 (S)를 이용하여 계산한다. 그러나, 하중-변위 측정 나노압입법에서는 탄성 및 소성변형만이 고려되고 시간 의존적 변형거동 (time dependent deformation; TDD)은 고려되지 않는다.(중략)

• Tunnel and Underground Space
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• v.8 no.2
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• pp.87-95
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• 1998

Field instrumentation and numerical analysis by the finite difference method were applied to estimate the relaxed zone in a subway tunnel of shallow depth in soft rock, excavated by NATM. The convergence and ground displacement can be used to estimate the deformation behavior and the relaxed zone. Parameters for the several models previously suggested were measured using regression analysis techniques adopting a function of time and the face advance. The estimated relaxed zone by the MPBX and FDM analysis were 1.5~3.0 m and 1.5~2.0 m, respectively. It was concluded that the visco-elastic model and the time-dependent elasto-plastic model correlate very well ($r^2$>0.9) with results of the numerical analyses.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.10a
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• pp.210-215
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• 1997

The development of rolling texture is dependent on the various rolling condition. And the geometry of rolling gab and the friction between rolls and rolled material mainly affect the type and sharpness of texture inhomogeneity through thickness. In order to follow the effect of geometry and friction various strain/pass and lubrication condition were applied during cold rolling. In this investigation various strain/pass and lubrication were applied during cold rolling in order to follow the effect rolling gap geometry and friction. More high 1/h was, more weak the ${\beta}$-fiber was and in the condition of l/h > 5 {001}<110> shear texture developed. In adition, rolling without lubrication enhanced the shear texture.

• Transactions of Materials Processing
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• v.22 no.7
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• pp.394-400
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• 2013

Microforming is a very efficient and economical technology to fabricate very small metallic parts in various applications. In order to extend the use of this forming technology for the production of microparts, the size effect, which occurs with the reduction of part size and affects the forming process significantly, must be thoroughly investigated. In this study, the tribological size effect in microforming was studied using modeling and scaled ring compression experiments. A micro-scale friction approach based on the slip-line field theory and lubricant pocket model was used to understand the friction mechanism and explain the tribological size effect. Ring compression tests were performed to analyze the interfacial friction condition from the deformation characteristics of the ring specimens. In addition, finite element analysis results were utilized to quantitatively determine the size-dependent frictional behavior of materials in various process conditions. By comparing theoretical results and experimental measurements for different size factors, the accuracy and reliability of the model were verified.

• Steel and Composite Structures
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• v.34 no.4
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• pp.615-623
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• 2020

In this paper, free vibration analysis of a functionally graded cylindrical nanoshell resting on Pasternak foundation is presented based on the nonlocal elasticity theory. A two-dimensional formulation along the axial and radial directions is presented based on the first-order shear deformation shell theory. Hamilton's principle is employed for derivation of the governing equations of motion. The solution to formulated boundary value problem is obtained based on a harmonic solution and trigonometric functions for various boundary conditions. The numerical results show influence of significant parameters such as small scale parameter, stiffness of Pasternak foundation, mode number, various boundary conditions, and selected dimensionless geometric parameters on natural frequencies of nanoshell.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.426-429
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• 2005

The fringe-field switching (FFS) mode associated with a transition from a homogenously aligned to twist deformation require rubbing process. In this devices, $1^o$ of misalignment in an azimuthal direction could cause voltage-dependent transmittance (V-T) to be different from that in a normal area and consequently results in a rubbing mura. According to our studies, the single domain FFS cells are much more sensitive to the rubbing mura than the dual domain FFS cell. Moreover, the FFS cells with negative LC are much more sensitive to the rubbing mura than the FFS cells with positive LC.