• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.672-675
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• 1995

Because of a sudden growth of the research of fatigue failure, recent machines or structures have been designed by damage tolerance design in many fields. Consequently, it is the most primary factor to clarity the specific character of fatique failure in the design of machines or structures considering reliability. A statistical analysis is required to analyze the outcome of an experiment or a life estimate by reason of that fatigue failure contains lots of random elements. Reliability analysis which has tukenn the place of the existing analyses in the consideration of the uncertainty of a material, is a very efficient way. Even reliability analysis, however, is not a perfect way to analyses the uncertainties of all the materials. This thesis would refer to a newly conceived data analysis that the coefficient of a system could cause the ambiguity of the relationship of an input and output.

• 대한기계학회논문집A
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• 제23권7호
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• pp.1104-1111
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• 1999

A brake pedal for the flight control system of the Korean primary trainer is developed using composite material. The development includes the structural design, stress analysis, manufacturing and the qualification tests. A FEM analysis is used for the structural design and stress analysis. Autoclaving process is used to fabricate the composite brake pedal. For the qualification tests, modular fixtures are developed and applied. It is shown that the composite brake pedal developed meets all the structural integrity requirements specified in the military specification for aircraft parts.

• 대한금속재료학회지
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• 제49권10호
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• pp.754-759
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• 2011

In this study, the interlaminar fracture behaviors of laminated GFRP composites were investigated, and the results could be used for damage tolerance design based on fracture mechanics. Three types of laminated GFRP composites that can be used as high voltage insulating materials in magnet systems were fabricated in order to study the interlaminar fracture behavior according to the molding process. The values of interlaminar fracture toughness for the VPI, prepreg, and HPL laminate were $1.9MPa{\cdot}^{1/2}$, $1.7MPa{\cdot}^{1/2}$, and $2.2MPa{\cdot}^{1/2}$, respectively. HPL laminate showed the best fracture resistance. The failure modes of HPL and VPI were similar to that of an adhesive joint, and prepreg laminates showed partial cohesive failure mode due to internal voids.

• 소성∙가공
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• 제26권1호
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• pp.28-34
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• 2017

Multi-pass shape rolling is performed to produce long products of arbitrary cross-sectional shapes. In the past, the multi-pass shape rolling process has been designed by the trial and error method or the experience of experts based on the empirical approach. Particularly, the design of roll caliber in shape rolling is important to improve product quality and dimensional accuracy. In this paper, the caliber design and pass schedule of multi-pass shape rolling were proposed for manufacturing piston ring wire. In order to design roll caliber, major shape parameter and dimension was determined by analysis of various caliber design. FE-simulation was conducted to verify effectiveness of proposed process design. At first, forming simulation was performed to predict shape of the product. Then, fracture of the wire was evaluated by critical damage value using normalized Cockcroft-Latham criteria. The experiment was carried out and the results are within the allowable tolerance.

• Current Research on Agriculture and Life Sciences
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• 제20권
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• pp.71-76
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• 2002

경북대학교 부속과수원에 재식되어 있는 봉옥, 기원방, 청도반시, 나주파시 품종의 휴면중인 1년생 가지를 2002년 1월에 채취하여 저온에 대한 내성을 검토한 결과 다음과 같은 결론을 얻었다. 1. 눈의 갈변도 측정에서는 $-15^{\circ}C$에서의 저온에 의한 갈변의 정도가 컸으며, 품종별의 차이는 나주파시의 경우 $-5^{\circ}C$일때의 저온에 대한 갈변의 정도와 $-15^{\circ}C$때와의 차이가 별로 없으며, 그 수치도 딴 품종에 비해 적었다. 2. 목질부의 갈변도 측정에서는 눈의 갈변도와 같은 경향으로 $-15^{\circ}C$일 때 피해가 컸으며, 품종별의 차이는 청도반시의 목질부에 대한 저온에 의한 갈변의정도가 딴 품종에 비해서 높았다. 3. 감의 주요 품종의 전기전도도를 보면 $-15^{\circ}C$일 때 전체적으로 저온의 피해가 컸으며, 나주파시와 봉옥의 경우 저온처리가 $-10^{\circ}C$이하일 경우에 E.C. 값이 다른 품종보다 눈에 띄게 큰 것으로 보아 이 품종은 저온에 대한 내성이 약하다는 것을 알 수 있다. 4. 눈의 맹아율은 $-15^{\circ}C$에서도 맹아가 되었으나 $-15^{\circ}C$일때의 맹아율이 타 온도보다 많이 적었는데, 나주파시의 맹아율이 가장 낮았으며, 기원방의 맹아율은 타품종에 비해 많이 높았다. 5. 위의 실험의 토대로 품종별 내한성의 차이를 전체적으로 비교한 결과 나주파시와 봉옥이 다른 품종보다 내한성이 낮으며, 기원방이 다른 품종보다 내한성이 높게 나타났었다.

• 한국항공우주학회지
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• 제50권6호
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• pp.377-384
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• 2022

복합재 항공기 구조물의 설계 시 인증을 고려한 재료 허용치와 설계치의 설정이 매우 중요하다. 그리고 복합재 구조물의 재료 허용치와 설계치의 설정은 정적강도, 손상허용 요구 조건 및 환경효과가 고려되어야 한다. 빌딩블록 접근법은 오랫동안 민간 및 군수 항공 산업에 적용되어 왔으며 중요한 인증 방법론을 제공하였다. 현재의 인증 방법은 시편, 요소, 부구성품 및 전기체 시험을 포함하는 광범위한 실험을 기반으로 한다. 본 논문에서는 복합재 허용치 실험 사례가 제시되며 빌딩 블록 접근 방식의 중요한 배경 및 적용방법이 제시된다.

• Structural Engineering and Mechanics
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• 제71권3호
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• pp.283-290
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• 2019

In global competition manufacturing companies have to produce modern, new constructions from advanced materials in order to increase competitiveness. The aim of my research was to develop a new composite cellular plate structure, which can be primarily used for structural elements of road, rail, water and air transport vehicles (e.g. vehicle bodies, ship floors). The new structure is novel and innovative, because all materials of the components of the newly developed structure are composites (laminated Carbon Fiber Reinforced Plastic (CFRP) deck plates with pultruded Glass Fiber Reinforced Plastic (GFRP) stiffeners), furthermore combines the characteristics of sandwich and cellular plate structures. The material of the structure is much more advantageous than traditional steel materials, due mainly to its low density, resulting in weight savings, causing lower fuel consumption and less environmental damage. In the study the optimal construction of a given geometry of a structural element of a road truck trailer body was defined by single- and multi-objective optimization (minimal cost and weight). During the single-objective optimization the Flexible Tolerance Optimization method, while during the multi-objective optimization the Particle Swarm Optimization method were used. Seven design constraints were considered: maximum deflection of the structure, buckling of the composite plates, buckling of the stiffeners, stress in the composite plates, stress in the stiffeners, eigenfrequency of the structure, size constraint for design variables. It was confirmed that the developed structure can be used principally as structural elements of transport vehicles and unit load devices (containers) and can be applied also in building construction.

• 로봇학회논문지
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• 제18권1호
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• pp.99-109
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• 2023

In this paper, the cinch bag typed fruit harvesting gripper was proposed. This gripper is focused on preventing problems that we found from the related research and setting the breakthrough as a design condition according to the harvest failures of other related studies. The cover part is designed to overcome the surrounding obstacles of target fruits such as tomato, Korean melon, and sweet pepper. The measurement of maximum load showed that the well-grasped target object, such as a spherical object with 65 mm of diameter, is unable to slip in a range of 0 kg to 10 kg. The fact that the gripper allows from 4 cm to 6 cm of positional error was shown in the measurement of positional error tolerance. And the cover part of this gripper showed that the suggested gripper can grab a target object without being obstructed by leaves and stems. Finally, it was proved that the gripper satisfied the design conditions through the measurement of contacting force, which showed it is appropriate for grasping an actual fruit without damage.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.116-120
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• 2004

A metal flaperon of a supersonic aircraft including the ribs, and skins was re-designed with a graphite/epoxy composite material to evaluate the weight saving effect. MSC/NASTRAN was used for the finite element analysis. The safety of the composite structures were evaluated in terms of the failure index, section cut, buckling, bearing/bypass and durability and damage tolerance analysis. After the application of the composite material, total weight saving of 25.6 pounds was achieved.

• 기계저널
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• 제35권6호
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• pp.468-480
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• 1995

항공기구조는 항상 피로하중에 노출되어 있고 조류충돌과 같은 불시의 상황에 의해 손상을 입을 가능성을 가지고 있어서 이에 대한 대비책을 마련하지 않으면 인명과 재산상에 막대한 손실을 초래할 가능성이 있다. 따라서 항공기가 개발되는 초기의 설계단계부터 항공기의 안전성확보가 중요하며, 이를 위해서는 적절한 피로수명예측과 손상허용설계를 해나아가는 것이 중요하며, 그 내용을 정리하면 다음과 같다. (1) 항상 손상의 가능성을 인정하고, 이 손상이 존재하는 경우에도 항공기의 안전이 보장 되도록 설계한다. (2) 손상이 발생하면 쉽게 발견되도록 설계한다. (3) 한 부재의 손상이 전 구조물의 파괴로 이루어지지 않도록 다중하중 경로로 설계한다. (4) 손상의 가능성이 있는 부품은 특별관리한다. (5) 안전균열성장 및 잔류강도 요구조건이 충족되도록 검사계획을 수립하며, 이 검사계획에 따라 검사를 수행한다.