• 콘크리트학회논문집
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• 제16권4호
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• pp.493-500
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• 2004

FREP(Fiber Reinforced Epoxy Panel)는 고인장강도, 경량성, 내부식성 및 시공성 등의 우수한 성질을 가지고 있어 손상된 RC보의 보강에 이용되고 있다. 본 연구에서는 RE보에 대한 사용 전 휨보강의 경우와 사용 중 휨보강의 경우에 대한 구성방정식을 정립하여 그 차이를 규명하고, 보강재 단부의 응력집중으로 인해 발생하는 단부박리파괴(rip-off failure)의 역학적 특성을 밝힘으로써 휨보강 효과 성능을 평가하였다. 연구결과 FREP로 휨보강된 철근콘크리트 보의 지배적인 파괴모드는 단부박리파괴이며, 본 연구의 실험 및 해석조건을 기준으로 RC 보강보의 단부박리파괴에 대한 평가를 실시한 결과 FREP 보강두께의 과다로 인한 보강단부의 급격한 휨강성의 변화로 응력집중 현상이 발생하여 단부박리파괴가 생긴다는 것을 알 수 있었다. 이는 보강 설계 시 단부박리파괴에 대한 평가가 반드시 필요한 것을 의미한다. 또한 FREP의 보강시기에 따른 보강효과를 분석한 결과 사용 전 보강(I-Type)에 비해 사용 중 보강(P-Type)의 보강효과가 감소하는 것으로 나타났다. 따라서, 기존 구조물과 같이 사용 중인 구조물을 보강하는 경우에는 이미 작용하고 있는 보강전하중(응력)으로 인한 발생 응력을 보강설계 시 고려하여야 할 것으로 판단된다.

• 대한조선학회논문집
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• 제29권4호
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• pp.202-213
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• 1992

선체(船體)의 횡강도(橫强度) 부재(部材)를 설계(設計)하기 위해서는 필수적(必須的)으로 횡강도(橫强度) 해석(解析)을 수반(隨伴)하여야 하며 이에 따라 많은 작업(作業) 시간(時間) 및 계산(計算) 시간(時間)이 필요(必要)하게 된다. 선체(船體)의 횡강도(橫强度) 해석(解析)을 위해 종래(從來)에는 경사(傾斜) 처짐법을 이용(利用)한 해석적(解析的) 방법(方法)이 사용(使用)되어 왔지만 부재(部材)의 신축(伸縮)을 무시(無視)함에 따라 해(解)의 정도(精度)가 상당히 낮을 뿐아니라 층방정식(層方程式)을 표현(表現)하기가 까다로워 프로그램 구성(構成)이 어렵다. 또한 최근(最近) computer의 발달(發達)과 함께 급속도(急速度)로 발전(發展)하고 있는 유한요소법(有限要素法)을 이용(利用)하여 선체(船體)의 횡강도(橫强度) 해석(解析)을 수행(遂行)하고 있지만 아직도 구조(構造) 설계(設計) 및 최적(最適) 구조(構造) 설계(設計)를 수행(遂行)하기에는 계산(計算) 시간(時間)의 극복(克服)이 어려운 실정(實情)이다. 본(本) 연구(硏究)에서는 선체(船體)의 구조(構造) 해석(解析) 및 설계(設計)를 위해 bracket이 붙은 부분을 span point 개념(槪念)을 도입(導入)하여 처리(處理)하고, 기존(旣存)의 경사(傾斜) 처짐법에서 무시(無視)하였던 부재(部材)의 신축(伸縮)에 따른 축방향(軸方向)의 변위(變位)를 고려(考慮)하여 각 절점(節点)에서의 평형방정식(平衡方程式)으로만 해(解)를 구할 수 있도록 하고 matrix method와 결합(結合)하여 2차원(次元) 및 3차원(次元)에 대한 일반화(一般化) 경사(傾斜) 처짐법을 유도(誘導)하였으며 기존(旣存)의 경사(傾斜) 처짐법 및 유한요소법(有限要素法)과 계산(計算) 시간(時間) 및 정도(精度)를 비교하여 본(本) 해석(解析) 방법(方法)의 우수성(優秀性)을 입증(立證)하였다.

• 한국의류학회지
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• 제12권2호
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• pp.169-179
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• 1988

In the part 1, relations were found between fundmental mechanical properties and primary hand values, performance of Korean women's summer fabrics. In this paper, in order to investigate the hand values and mechanical properties such as tensile, shearing, bending, compression, surface and thickness & weight of the women's fall & winter fabrics were measured by KES-F system. Sorts of 90 commercial fabrics for women's fall & winter clothes were classfied into 39 silk and 51 polyester fabrics according to meterials. The experimental results were analysed statistically to relate the hand values and the mechanical properties and concerning to formation of weared clothes and transformation behavior were investigated. Furthermore, there mechanical properties as well as their hand values were discussed in comparison with those values for kimono fabrics. The main results are summarized as follows; 1. The shape of silk fabrics in formation for weared clothes show a box-shaped silhouette. Polyester fabrics has a easy to shape-less and make a silhouette which goes along with the body. 2. Silk fabrics for Korean women's fall & winter clothes have ${\pm}1\sigma$ range of bending, shearing, surface properties and thickness as compared with kimono fabrics. 3. A wrinkle recovery and drapability of silk fabrics for Korean women's fall & winter clothes are inferior to kimono fabrics. On the other hand, the fabrics for Korean women's fall & winter clothes have conical-shaped silhouette based on higher bending rigidity. 4. Except for flexibility with soft feeling, a primary factor of mechanical properties contributes to the hand values of fabrics for Korean women's fall & winter clothes having no concern with materials were same as the women's summer fabrics. 5. As for the hand values of fabrics for Korean folk clothes, stiffness, anti-drape stiffness are larger than those of kimono fabric and stiffness, anti-drape stiffness, crispness of fabrics for Korean women's fall & winter clothes have smaller values as compared with Korean women's summer fabrics.

• 한국강구조학회 논문집
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• 제20권5호
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• pp.601-608
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• 2008

단층 래티스 돔에 사용되는 접합부는 그 형태나 접합방법에 따라 다양한 거동 특성을 지닌다. 볼 조인트의 경우, 다루기 쉽고 현장 적용에 유리하지만, 강성과 내력이 약하기 때문에 장스팬의 확보에 있어서 불리하다. 용접 접합부는 볼 조인트에 비해 강성과 내력이 우수하고, 장스팬을 확보할 수 있지만, 용접 접합부에 관한 연구 및 실험은 드문 실정이다. 본 연구에서는 단층 래티스 돔에 적용 가능한 용접 접합부를 제안하고, 이를 기존접합부와의 비교하기 위한 실험을 수행하였다. 또한 제안된 접합부에 대해 삽입 플레이트의 길이, 두께, 여장을 변수로 하여 각각의 변수에 의한 실험체의 거동의 변화를 살펴보았다. 실험을 통한 결과를 토대로 하여 새로운 형태의 용접 접합부를 제안하고자 한다.

• Computers and Concrete
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• 제14권6호
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• pp.695-710
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• 2014

This paper presents a theoretical and computational approach to solve inelastic structures subjected to overloads. Current practice in structural design is based on elastic analysis followed by limit strength design. Whereas this approach typically results in safe strength design, it does not always guarantee satisfactory performance at the service level because the internal stiffness distribution of the structure changes from the service to the ultimate strength state. A significant variation of relative stiffnesses between the two states may result in unwanted cracking at the service level with expensive repairs, while, under certain circumstances, early failure may occur due to unexpected internal moment reversals. To address these concerns, a new inelastic model is presented here that is based on the nonlinear material response and the interaction relation between axial forces and bending moments of a beam-column element. The model is simple, reasonably accurate, and computationally efficient. It is easy to implement in standard structural analysis codes, and avoids the complexities of expensive alternative analyses based on 2D and 3D finite-element computations using solid elements.

• Fibers and Polymers
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• 제6권3호
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• pp.186-199
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• 2005

A selection of commercially available poly(ethy1ene terephtha1ate) fibers with different degrees of molecular alignment and crystallinity have been investigated utilizing a wide range of techniques including optical microscopy, infrared spectroscopy together with thermal and wide-angle X-ray diffraction techniques. Annealing experiments showed increased molecular alignment and crystallinity as shown by the increased values of birefringence and melting enthalpies. Crystallinity values determined from thermal analysis, density, unpolarized infrared spectroscopy and X-ray diffraction are compared and discussed in terms of the inherent capabilities and limitations of each measurement technique. The birefringence and refractive index values obtained from optical microscopy are found to decrease with increasing wavelength of light used in the experiments. The wide-angle X-ray diffraction analysis shows that the samples with relatively low orientation possess oriented non-crystalline array of chains whereas those with high molecular orientation possess well defined and oriented crystalline array of chains along the fiber axis direction. X-ray analysis showed increasing crystallite size trend with increasing molecular orientation. SEM images showed micro-cracks on low oriented fiber surfaces becoming smooth on highly oriented fiber surfaces. Excellent bending characteristics were observed with knotted fibers implying relatively easy fabric formation.

• 소성∙가공
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• 제24권4호
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• pp.280-286
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• 2015

Hemming is used to connect two sheet metal components by folding the edge of an outer panel around an inner panel to create a smooth edge. The minimization of hemming defects is critical to the final quality of automobile products because hemming is one of the last operations during fabrication. Designing the hemmed part is not easy and is influenced by the geometry of the bent part. Therefore, the main problem for automotive parts is dimensional accuracy since formed products often deviate geometrically due to large springback. Few numerical approaches using 3-dimensional finite element model have been applied to hemming due to the small element size which is needed to properly capture the bending behavior of the sheet around small die corner and the comparatively big size of automotive opening parts, such as doors, hoods and deck lids. The current study concentrates on the 3-dimensional numerical simulation of hemming for an automotive door. The relationship between the design parameters of the hemming operation and the height difference defect is shown. Quality improvement of the automotive door can be increased through the study of model parameters.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.742-745
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• 2004

The FRP-concrete composite deck system has advantages of corrosion free and easy construction. The system is, however, comprised of two brittle materials, so that it suffers from inherent disadvantage of lack of ductility. In this study, some conceptual design is presented for preventing the brittle failure of FRP-concrete composite deck at ultimate load level. 4-point bending tests are performed for FRP-concrete composite beams using FRC(Fiber Reinforced Concrete). The specimens use the box-shape FRP member in the lower portion. Four types of concrete with different compressive strengths and ductilities including normal mortar and 3 FRCs are placed in the upper portion. Typical failure mode in the test is identified; Concrete compressive failure occurs first at the maximum moment region, and the interfacial debonding between FRP and concrete member proceeds. Finally, the tensile rupture of FRP member occurs. The specimen using FRC with the high compressive ductility of concrete fails with less brittle manner than other specimens. The reason is that the ductility from the concrete in compression prevents the sudden loss of load-carrying capacity after compressive concrete failure.

• 한국정밀공학회지
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• 제13권7호
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• pp.100-114
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• 1996

In order to create a solid model more efficiently for a plastic or sheet metal product with a thin and constant thickness, various methods have been proposed up to now. One of the most typical approaches is to create a sheet model initially and then transform it into a solid model automatically for a given thickness. The sheet model as well as the transitive model in sheet modeling procedure is a non-manifold model. However, the previous methods adopted the boundary representations for a solid model as their topological framework. Thus, it is difficult to represent the exact adjacency relationship between topological entities and to implement the topological operations for sheet modeling and the transformation procedure of a sheet into a solid. In this paper, we proposed a sheet modeling system based on a non-manifold topological representation which can represent solids, sheets, wireframes, and their mixture. A set of generalized Euler operators for non-manifold topology as well as the sheet modeling capabilities including adding, bending, and punching functions are provided for easy modeling of sheet objects, and they are perfomed interactively with a two dimensional curve editor. Once a sheet model is completed, it can be transformed into a solid automatically. The transformation procedure is composed of the offset functions and the Boolean operations of sheet models, and it is even more comprehensive and easier to be implemented than the precious methods.

• 한국압력기기공학회 논문집
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• 제14권1호
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• pp.24-31
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• 2018

The mechanical design procedure is studied for the PCHE(printed circuit heat exchanger) with electrochemical etched flow channels. The effective heat transfer plates of PCHE are assembled by diffusion bonding to make a module. PCHE is widely used for industrial applications due to its compactness, cost efficiency, and serviceability at high pressure and/or temperature conditions. The limitations and technical barriers of PCHE are investigated for application to nuclear components. Rules for design and fabrication of PCHE are specified in ASME Section VIII but not in ASME Section III of nuclear components. Therefore, the calculation procedure of key dimensions of PCHE is defined based on ASME section VIII. The effective heat transfer region of PCHE is defined by several key dimensions such as the flow channel radius, edge width, wall thickness, and ridge width. The mechanical design procedure of key dimensions was incorporated into a program for easy use in the PCHE design. The effect of assumptions used in the key dimension calculation on stress values is numerically investigated. A comparative analysis is done by comparing finite element analysis results for the semi-circular flow channels with the formula based sizing calculation assuming rectangular cross sections.