• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.312-315
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• 2002

This paper summarizes the results of a numerical study conducted to analyze the effect of selected process parameters on material flow and thread profile in thread rolling of large diameter blanks. Based on the previous work where a plane strain mode was found to provide a reasonable approximation of the thread rolling process, the effect of varying thread form, friction factor, flow stress, and blank diameter on effective strain and thread height was analyzed using the finite element code DEFORM. This study show that effective strain for flank angle, that blank diameter had important effect on the as-rolled thread while flow stress, friction factor, and crest round of dies had significant impact on effective strain at the thread root and crest and load of thread rolling. While the rate of strain harding was found to have an effect on the crest profile, the results indicate that it is the primary factor responsible for seam formation in rolled threads.

• Steel and Composite Structures
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• 제45권4호
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• pp.605-619
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• 2022

The tensile behavior of the Thread-fixed One-side Bolt (TOB) at high temperatures was studied using the Finite Element Modeling (FEM) to explore the structural responses that could not be measured in tests. The accuracy of the FEM was verified using the test results from the failure mode, load-displacement curve as well as yielding load. Three typical failure modes of TOB connected T-stubs were observed, which were the Flange Yielding (FY), the Bolt Failure (BF) and the Coupling Failure mode (CF). The influence of the flange thickness tb and the temperature θ on the tensile behavior of the T-stub were discussed. The initial stiffness and the yielding load decreased with the increase of the temperature. The T-stubs almost lost their resistance when the temperature exceeded 700℃. The failure modes of T-stubs were mainly decided by the flange thickness, which relates to the anchorage of the hole threads and the bending resistance of flange. The failure mode could also be changed by the high temperature. Design equations in EN 1993-1-8 were modified and verified by the FEM results. The results showed that these equations could predict the failure mode and the yielding load at different temperatures with satisfactory accuracy.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.71-75
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• 2000

The effects of stitching thread on fatigue characteristics of polyurethane foam cored sandwich structures are investigated. Fatigue test and static test, being used in four point bending test, are performed with various diameters and distances of stitching thread. The Results show that the maximum load for bending tests is similar to each other, but after $1O^6$ fatigue cycles, the stiffness degradation of the stitching thread diameter $\emptyset$ 3mm specimen is a much larger than that of the $\emptyset$ 5mm specimen.

• 정보처리학회논문지C
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• 제11C권3호
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• pp.337-344
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• 2004

본 논문은 다중 프로세서(Multiprocessor) 기반 다중 쓰레드(Multithreaded) 구조의 네트워크 프로세서를 이용한 패킷 치리 시스템에서 패킷을 보다 고속으로 처리하기 위한 쓰레드 스케줄링 기법을 제안한다 이를 위하여 스케줄링과 관련한 인자를 실험을 통하여 얻고, 패킷 내용 및 다중 쓰레드 아키텍쳐를 표현하는 인자를 포함하도록 설계하였다. 시뮬레이터를 이용한 실험을 통하여 제안된 스케줄링 기법이 제공하는 처리율 및 부하 분산 정도가 다른 스케줄링 기법과 비교하여 효율적임을 증명하였다.

• 구강회복응용과학지
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• 제29권2호
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• pp.111-118
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• 2013

본 연구는 삼차원적 유한요소분석을 통하여 연결부 형태가 다른 두 가지 scallop 임플란트의 경부 나사선 피치가 응력 분포에 미치는 영향을 간접적으로 확인하고자 하였다. 4가지 경부 나사선 피치 (0.4mm, 0.5mm, 0.6mm, 0.7mm)를 갖는 scallop 임플란트를 두 가지 다른 연결부 형태 (platform matching connection, platform mismatching connection)로 지대주와 연결되는 유한요소모형을 설계하였다. 8개의 모든 모델에 100N의 하중을 수직 및 30도 경사 방향으로 인가하여, 임플란트, 지대주, 그리고 치조골에 가해지는 최대등가응력을 분석하였다. 유한요소분석결과 응력은 치밀골에 집중되었다. 작은 나사 피치가 설계된 platform mismatching connection 모델에서 수직 방향과 경사하중 시 최대등가응력이 가장 낮게 나타났다. 측정되었다. Platform matching connection 모델에서는 경사하중의 경우 0.6mm, 수직하중의 경우 0.4mm 나사 피치에서 가장 낮은 최대등가응력을 보였다. 따라서 scallop 임플란트에서 platform mismatching connection은 최대등가응력을 감소시키는 데 중요한 역할을 하며, 경부 나사 피치가 작을수록 최대등가응력이 감소되는 경향을 보임을 알 수 있었다.

• Elastomers and Composites
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• 제44권4호
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• pp.391-396
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• 2009

본 연구에서는 전조공정의 수치해석을 수행하였다. 해석을 이용한 공정 인자 설계에 앞서서, 효율적이고 신뢰성 있는 해석을 위한 해석 조건에 대하여 연구를 수행하였다. 치형의 개수와 요소의 수에 대한 해석 결과를 바탕으로 해석의 정도를 보장하고 효율적으로 해석을 수행할 수 있는 조건을 설정하였다. 그리고, 프랭크 각도와 치형의 끝단부 라운드 등의 금형의 형상과 성형 온도가 유효 응력, 유효 변형율, 전조력, 그리고 크랙 발생에 미치는 영향을 알아보았다. 해석은 DEFORM-3D를 이용하여 수행하였다. 프랭크 각도와 치형의 끝단 부 라운드는 전조력에 영향을 미치는 것을 확인할 수 있었으며, 성형 온도 조건에 따라서 유효 변형률과 전조력, 그리고 크랙을 예상 할 수 있었다.

• 대한치과보철학회지
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• 제44권2호
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• pp.185-196
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• 2006

Statement of problem: The researches on the influence of design variables on the stress distribution in cortical and trabecular bones and on optimal design for implant system were limited. Purpose: The purpose of this study is to identify the sensitivities of design parameters and to suggest the optimal parameters for designing the onebody type implant system. Material and methods: Stresses arising in the implant system were obtained by finite element analysis using a three dimensional model. An onebody type implant system[Oneplant (Warrantec. Co. Ltd., Korea)] was considered in this study. Vortical load(150 N) was applied on the top of the abutment along the axial direction. The initial design variables set for sensitivity analysis were radius of fixture, numbers of micro thread, numbers of power thread, height of micro thread, future length, tapered angle of future, inclined angle of thread, width of micro thread and width of power thread. The statistical technique of Design of Experiments(DOE) was applied tn the simulation model to deduce effective design parameters on stress distributions in bones. The deduced design parameters were incorporated into a fully automated design tool which is coupled with the finite element analysis and numerical optimization to determine the optimal design parameters. Results: 1. The result of sensitivity analysis showed six design variables - radius of future, tapered angle of fixture, inclined angle of thread, numbers of power thread, numbers of micro thread and height of micro thread - were more influential than the others. 2. The optimal values of design variables can be deduced by coupling finite element analysis (FEA) and design optimization tool(DOT).

• 대한토목학회논문집
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• 제31권3A호
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• pp.189-198
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• 2011

각국 강구조물 시공현장에서 사용되고 있는 고장력볼트의 인장강도는 1,000 MPa급이 주종을 이루고 있으나, 고강도강과 극후판의 개발과 강교량 건설기술의 발전에 따른 교량 지간의 장대화로 인하여 강도가 큰 새로운 볼트 개발이 요구되고 있다. 현재, 인장강도 1,300 MPa급의 고장력볼트가 개발되어 사용중에 있다. 그러나 고장력볼트는 작은 단면에 큰 하중이 작용하기 때문에 고강도볼트에서는 응력집중이 완화된 나사형상과 구조성능이 우수한 고장력볼트가 보다 효과적이다. 본 연구에서는 KS에서 규정된 나사형상보다도 우수한 나사형상을 개발하기 위하여 해석적 연구를 수행하였다. 나사형상에 대한 특성을 분석하여 볼트와 너트 체결시에도 하중분배가 효과적이고 응력집중이 완화된 신나사형상을 제안하였다. 또한, 실험적 연구에서는 인장강도 1,300 MPa급의 고장력볼트를 대상으로 구조성능에 대해서 실험연구를 수행하였다. 연구결과 신나사형상이 기존의 나사형상보다도 응력집중 완화효과와 구조성능효과가 있음이 검증되었다.

• 한국안전학회지
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• 제29권5호
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• pp.74-81
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• 2014

This study proposes an advanced type of a micropile system. The proposed micropile system consists of perfobond ribs installed steel rod to improve shear capacity between the thread and the grout, and partially expanded drill holes to increase resistance capacity between the grout and the ground. This study contains experimental evaluations on the proposed micropile system to verify the shear capacity of perfobond rib installed on the steel rod and the load-carrying capacity of shear key created by the partially expanded drill hole. Push-out tests were conducted on a rolled screw thread and steel rods which perfobond ribs are installed instead of rolled screw, in order to compare their load-carrying capacity and behavioral characteristics. As a result, it was confirmed that the perfobond-rib steel rods show much superior structural behavior in terms of initial stiffness, ultimate load, and ductile behavior.

• 한국정밀공학회지
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• 제22권3호
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• pp.179-186
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• 2005

A comparative study of stress distributions in the maxillary bone with three different types of abutment was conducted. Finite element analysis was adopted to determine stress generated in the bone with the different implant systems with micro threads (Onebody type implant, Internal type implant, and External type implant). It was found that the types of abutments and the number of micro threads have significant influence on the stress distribution in the maxillary bone. They were due to the difference in the load transfer mechanism and the size of contact area between abutment and fixture. Also the maximum effective stress in the maxillary bone was increased with increasing inclination angle of load. It was concluded that the maximum effective stress in the bone was the lowest by the internal implant among the maximum effective stresses by other two types of implants and by appropriate number of micro threads, and that the specific number of micro thread was existed to decrease the maximum effective stress in the maxillary bone due to different implant systems and loading conditions.