• 대한치과보철학회지
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• 제34권2호
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• pp.385-402
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• 1996

The purpose of this study was to analyze how the stability of the implant prostheses and the loosening of the fastening screw was affected when the various types of Hex structure provided for the effect of anti-rotation of the single prostheses were given. Three dimensional finite element model was designed with which the implants with the external hex type of 0.75mm, 1.5mm and the implant with the internal hex type of 0.75mm, 1.5mm and the implant with the external hex type of $15^{\circ}$ tapered shape of 0.75mm were supposed to completely osseointegrate to the mandible. After fininshing the finite element model, the preload of 10N at the fastening screw was applied and then the vertical and $30^{\circ}$ lateral load of 200N was applied respectively at the cusp tips of the prostheses. The following results were obtained : 1. In case of displacement, the amount of displacement was increased at the internal hex type(model C, D) than at the external hex type(model A, B, E) when the vertical and lateral load was applied. 2. Less equivalent stress was represented at the model B with increased external hex height than at the model A when the vertical and lateral load was applied. 3. Much stress was represented at the model E with increased hex angle than at the model A in case of the stress happened to the implant body and the fastening screw when the vertical and lateral load was applied. 4. Much equivalent stress was represented at the model D with deepened internal hex height than at the model C when vertical and lateral load was applied. 5. The least stress was taken at the model B and the most stress was taken at the model D in case of the stress happened to the implant when the vertical and lateral load was applied. 6. The least stress was taken at the model C at the vertical load. And the least stress was taken at the model B at lateral load in case of the stress happened to the fastening screw. As a results of this study, the good lateral stability of prostheses and less stress of the component of implant was taken when the external hex height was increased, and the risk of neck fracture of implant and fastening screw was increased when the internal hex height was deepned because of long screw neck portion and thin implant neck portion.

• Journal of Biosystems Engineering
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• 제41권3호
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• pp.153-160
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• 2016

Purpose: This study was conducted to experimentally investigate the structural safety of and identify critical locations in a front-end loader under impact loads. Methods: Impact and static tests were conducted on a commonly used front-end loader mounted on a tractor. In the impact test, the bucket of the front-end loader with maximum live load was raised to its maximum lift height and was allowed to free fall to a height of 500 mm above the ground where it was stopped abruptly. For the static test, the bucket with maximum live load was raised and held at the maximum lift height, median height, and a height of 500 mm from the ground. Strain gages were attached at twenty-three main locations on the front-end loader, and the maximum stresses and strains were measured during respective impact and static tests. Results: Stresses and strains at the same location on the loader were higher in the impact test than in the static test, for most of measurement locations. This indicated that the front-end loader was put under a severe environment during impact loading. The safety factors for stresses were higher than 1.0 at all locations during impact and static tests. Conclusions: Since the lowest safety factor was higher than 1.0, the front-end loader was considered as structurally safe under impact loads. However, caution must be exercised at the locations having relatively low safety factors because failure may occur at these locations under high impact loads. These important design locations were identified to be the bucket link elements and the connection elements between the tractor frame and front-end loader. A robust design is required for these elements because of their high failure probability caused by excessive impact stress.

• Restorative Dentistry and Endodontics
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• 제16권1호
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• pp.133-150
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• 1991

To study the mechanical behavior depended on the restoration method and alveolar bone height at endodontically treated teeth. a finite element model was made which was applied by four types of restoration methods and alveolar bone height on upper central incisor and then 1 Kg force was applied on each model as follows; 1) $45^{\circ}$ diagonal load on incisal edge. 2) $26^{\circ}$ diagonal load on lingual surface. and 3) horizontal load on labial surface. The author analyzed the displacement and stress of teeth and their supporting tissue by finite element method according to three type of loading conditions. The results were as follows : 1. The displacement by restoration method and the stress in dentin was found greater in restoration without a post than in that with a post. 2. The displacement and stress was found about the same when compared : A) in Resin model and PFM model applied by restoration method without a post and B) in PRC model and CPC model applied by restoration method with a post. 3. The lower alveolar bone height was. the greater was the displacement and stress. 4. The lower alveolar bone height was. the greater slightly was the stress of restoration without a post than in that with a post. 5. The stress in loading condition was the greatest in P1 in dentin and post. and was greatest in P3 in alveolar hone. 6. In the restoration method without a post. stress concentration in labial dentin was distributed to a figure of long belt in adjacent part to periodontal ligament. while in restoration method with a post. it was distributed in adjacent part to post side. And in all types of restoration method stress concentration in alveolar bone was distributed along the compact bone of labial and lingual surface.

• 문화기술의 융합
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• 제6권4호
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• pp.753-760
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• 2020

본 연구에서는 정밀 3차원 수치해석모델을 이용하여 수직하중(받침설계하중)과 수평하중(지진시 발생되는 수평력)을 적용하여 교량받침 교체시 보자리의 구조적 안전성에 대한 검토를 수행하였다. 기존 콘크리트와 교량받침 교체로 인해 새로 타설된 콘크리트의 응력 및 용접된 철근에 발생하는 응력 및 변위 결과를 수치해석적으로 확인하였다. 수치해석결과, 수평력 및 보자리 높이 증가는 신구콘크리트 경계면의 발생응력의 증가에 따른 콘크리트 균열(파괴) 및 내부 철근연결부의 응력증가를 초래하는 것으로 분석되었다. 따라서 보자리 높이 증가는 수평력의 크기와 직접적인 상관관계가 있으며 받침 용량에 적합한 보자리 높이 적용이 필요할 것으로 분석되었다. 본 연구에서는 보자리에 작용하는 수평력의 크기와 보자리 높이와의 상관관계를 변수로한 받침교체공사 가이드라인을 도표로 제시하여 교량받침 용량에 적합한 보자리 높이 설정 및 보강유무를 결정하는 방안을 제시하였다.

• Structural Engineering and Mechanics
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• 제41권2호
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• pp.299-312
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• 2012

Stiffened coupled shear walls (SCSW) are under axial load resulting from their weight and this axial load affects the behavior of walls because of their excessive height. In this paper, based on the continuum approach, the optimal position of the stiffening beam on the stiffened coupled shear walls is investigated considering the effect of uniformly distributed axial loads. Moreover, the effect of the height of stiffened coupled shear walls on the optimal position of the stiffening beam has been studied with and without considering the axial force effect. A computer program has been developed in MATLAB and numerical examples have been solved to demonstrate the reliability of this method. The effects of the various flexural rigidities of the stiffening beam on the internal forces and the lateral deflection of the structure considering axial force effect have also been investigated.

• 한국환경과학회지
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• 제9권5호
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• pp.389-392
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• 2000

In this study a packed tower was selected for the treatment apparatus of $NH_3$ gas produced in industry. Formerly latticework packing has been used in preventive facility of treatment of $NH_3$ gas. However recently metallic Ralu-Pack 250YC. structured packing is usually being used in petrochemical production plant. This study is for the application the packing to the $NH_3$ gas treatment in wet scrubbing process. In Air/water system hydraulic pressure drop dependent of specific liquid load and gas capacity factor was continuous and parallel from graph. The tower height can be determuined by the number of transfer unit and the height of transfer unit influenced on liquid distribution.

• 대한조선학회지
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• 제22권3호
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• pp.1-8
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• 1985

In this paper, the motion response and wave load of a container ship are treated by a nonlinear motion theory, which is similar to that used by Yamamoto et. al.[1]. This paper deals with the vertical motion response in oblique waves and the effect of the Smith correction in buoyancy force calculation. In the present computation, for S-175 container ship model our result also shows that the ratio of the motion peak to peak value to the wave height decreases as the wave height increases, which was obtained earlier by Yamamoto et.al.[3]. On the other hand the nondimensional midship bending moment increases as the wave height increases. These nonlinear effects are dominant near the resonance frequency, and depend on the hull form and forward speed. However, it is found that these nonlinear effects are significant for tanker model.

• Structural Engineering and Mechanics
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• 제18권6호
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• pp.745-757
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• 2004

Lateral-torsional buckling moment resistances of I-shaped stepped beams with continuous lateral top-flange bracing under a single point load on the top flange and negative end moments were investigated. Stepped beam factors and a moment gradient correction factor suggested by Park et al. (2003, 2004) were used to develop new lateral buckling formula for beam designs. From the investigation of finite element analysis (FEA), new lateral buckling formula of beams with singly or doubly stepped member changes and with continuous lateral top-flange bracing subjected to a single point load on top flange and end moments were developed. The new design equation includes the length-to-height ratio factor to account for the increase of lateral-torsional buckling moment resistance as the increase of length-to-height ratio of stepped beams. The calculation examples for obtaining lateral-torsional buckling moment resistance using the new design equation indicate that engineers should easily determine the buckling capacity of the stepped beams.

• 산업경영시스템학회지
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• 제25권4호
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• pp.40-45
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• 2002

An AS/RS construction cost minimization model under throughput rate requirement constraint has been developed, whose objective function includes S/R machine cost, storage rack cost, and interrace conveyor cost. S/R machine cost is a function of the storage rack height, the unit load weight, and the control logic used by the system, while storage rack cost is a function of the storage rack height, the weight and the volume of the unit load. Since the model is a nonlinear integer programming problem which is very hard to solve exactly with large problem size, a solution procedure is developed to determine the height and the length of the storage rack with a fixed number of S/R machines, while increasing the number of S/R machines one by one to meet the throughput rate requirement.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.173-177
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• 2005

The heat/mass transfer characteristics on the plane tip surface of a high-turning first-stage turbine rotor blade has been investigated by employing the naphthalene sublimation technique. The heat/mass transfer coefficient is measured for four tip clearance height-to-chord ratios of h/c = 1.0%, 2.0%, 3.0%, and 4% at the Reynolds number of $2.09{\times}105$. The result shows that at lower h/c, there exists a strong flow separation/re-attachment process, which results in severe thermal load along the pressure-side comer. As h/c increases, the re-attachment is occurred further downstream of the pressure-side comer with lower thermal load. At higher h/c, a pair of vortices on the tip surface near the leading edge are found along the pressure-side and suction-side comers, and the pressure-side tip vortex have significant influence even on the mid-chord local heat transfer.