• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.10
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• pp.963-970
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• 2015

Laminate structures are used in the automobile, aerospace, and display industries. The advantages of fiber metal laminates are well known. Fiber metal laminates are useful for reducing the weight and improving impact resistance . However, currently, the mechanical properties of fiber metal laminates are not derived. In this paper, we use thickness as a factor for comparing the properties of laminates of various thickness combinations. The properties fiber metal laminates are analyzed using design of experiments. In addition, the finite element method is used to analyze elastic and plastic strains of fiber metal laminates and aluminum plates. The final goal of this paper is to find a suitable finite element model of fiber metal laminates under bending.

• Journal of Ocean Engineering and Technology
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• v.8 no.2
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• pp.105-114
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• 1994

초경합금은 기계적 성질이 다른 WC의 분상상과 Co의 결합상으로 구성되어 있다. 만일 이합금이 거시적으로 균일하게 변형을 하면, 각 상들은 이들의 응력상태에 따라 다르게 변형될 것이다. 따라서 WC-Co 합금의 변형특성과 강화기구를 명확히 알기 위해서는 각상의 미시적 변형과 파괴기구를 검토할 필요가 있다. 본 연구에서는 시편에 굽힘하중을 가하여, X선 회절로 분산상인 WC상 및 결합상인 Co상의 X선적 탄성정수와 응력정수를 측정하였다. WC-Co합금중의 WC상과 Co상의 상응력은 WC(112)면과 CO(311)면의 회절로서 결정하였다. 그리고 이 상응력들을 복합법칙의 적용가능성에 대하여 검토하였다.

• Journal of Dental Rehabilitation and Applied Science
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• v.32 no.3
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• pp.169-175
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• 2016

Purpose: Direct splinting material should have high flexural strength to withstand force during mastication and low modulus of elasticity to provide some movement while force applied for relief of stress. The purpose of this study was to compare flexural strength and modulus of elasticity of several resinous splinting materials. Materials and Methods: Four materials; Super-Bond C&B, G-FIX, G-aenial Universal Flo, FiltekTM Z350 XT; were used in this study. Fifteen rectangular bar specimens of each material were prepared. Three-point bending test were performed to determine physical properties. Maximum load at fracture was recorded and flexural strength and modulus of elasticity were calculated. One-way analysis of variance (ANOVA) and Scheffe's tests at a 0.05 level of significance were conducted on all test results. Results: Statistical analysis reveals that Super-Bond C&B had significant low mean value for flexible strength and the other three materials showed no significant difference. For modulus of elasticity, Super-Bond C&B exhibited statistically lower modulus of elasticity. G-FIX presented intermediate result, showing statistically higher modulus of elasticity than Super-Bond C&B but lower than G-aenial Universal Flo and FiltekTM Z350 XT. There was no significant difference on modulus of elasticity between G-aenial Universal Flo and FiltekTM Z350 XT. Conclusion: Using a G-FIX, the newly commercially available splinting material, which shows higher fracture resistance properties comparable to flowable and restorative composite resin and a relatively flexible nature might be a beneficial for stabilizing teeth mobility.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.4
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• pp.307-314
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• 2009

The present paper briefly describes the space frame element and the fundamental strategies in computational elastic bifurcation theory of geometrically nonlinear, single load parameter conservative elastic spatial structures. A method for large deformation(rotation) analysis of space frame is based on an eulerian formulation, which takes into consideration the effects of large joint translations and rotations with finite deformation(rotation). The local member force-deformation relationships are based on the beam-column approach, and the change in member chord lengths caused by axial strain and flexural bowing are taken into account. and the derived geometric stiffness matrix is unsymmetric because of the fact that finite rotations are not commutative under addition. To detect the singular point such as bifurcation point, an iterative pin-pointing algorithm is proposed. And the path switching mode for bifurcation path is based on the non-negative eigen-value and it's corresponding eigen-vector. Some numerical examples for bifurcation analysis are carried out for a plane frame, plane circular arch and space dome structures are described.

• Composites Research
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• v.19 no.6
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• pp.23-31
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• 2006

We measured mechanical properties, including Young's modulus, effective bending modulus and nominal fracture strength of nanohoneycomb structures using an Atomic Force Microscope(AFM) and a Nano-Universal Testing Machine(UTM). Anodic aluminum oxide(AAO) films are well suited as nanohoneycomb structures because of the simple fabrication process, high aspect ratio, self-ordered hexagonal pore structure, and simple control of pore dimensions. Bending tests were carried out for cantilever structures by pressing AFM tips, and the results were compared with three-point bending tests and tensile tests using a Nano-UTM. One side of the AAO films is clogged by harrier layers, and looks like a face material of conventional sandwich structures. Analysis of this layer showed that it did not influence the bending rigidity, and was just a crack tip. The present results can act as a design guideline in applications of nanohoneycomb structures.

• Journal of the KSME
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• v.17 no.1
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• pp.32-39
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• 1977

파괴역할적으로 피로문제를 다룰 때는 언제나 crack의 존재를 전재로 한다. 재료가 피로하중을 받아 파괴에이르는 과정의 설명은, 일차적으로는 피로에의한 crack의 발생이고, 다음단계로는 발 생한 crack들의 상호연결 또는 성장을 거쳐 최종적으로 파단에 이른다는 순서로 이루어진다고 보 기 때문이다. 또한, crack의 존재를 전제로 하더래도 crack청단의 응력장이 탄성론적으로 해석될 수 있어야함도 절대적인 전제가 되고 있다. 모든 피로제엔 각경형태의 crack발생, 성장이 관찰되 고 있는데, 이들 모든 crack들이다. 파괴역학적으로 다루어 질 수 있는 것은 물론 아니고, 아직도 K해석이 도어있지 않은 crack들이 많이 남아 있는 것이다. 예컨대 회전굽힘 피로시험편에서 관찰 되는 각종 형태의 표면피로 crack들은 응력해석의 곤란 때문에 아직은 이들에 적용시킬 K의 표 식이 없는 실정이라 하겠다. 이들 crack에 대해서는 K해석 뿐만 아니고, 피로역학적인 다른 Factor 즉 $r_{p}$라든가 .phi.같은 것들도 이해색상태에 있어 이 분야에의 연구가 많이 기대되고 있는 실정이다. Crack에 대한 연구는, 그것이 파괴의 전제가 되기 때문에 큰 의의를 갖는다고 보 겠는데 표면 Crack이 연결 또는 성장해서 시편의 전주를 완전히 일주 했어도 그것만으로는 바로 재료의 파괴에 직결이 되지 않는 것도 이 시험편의 특색이라 하겠다. 물론 회전굽힘 피로시험편 외에도 K해석이 되어있지 않은 경우는 아직도 많으며, K가 해석되어 있는 경우에 대해서도 정확 한 경계조건 등을 잘 검토해 가면서 응용함이 옳을 것이다. 화전굽힘피로의 경우나 그밖의 예에 서와같이 정확한 K해석이 이루어져 있지 않드래도 연구자에 따라 "Effective Streess Intensity Factor"라는 것을 쓰는 예도 왕왕있는데, 이에는 상당한 검토와 타당성제가 요구되고 있으며, 그 사용가능성여부에 대해서는 논란이 많이 따르는데 상례이기도 하다. 몇가지의 피로구열해석예를 들어보기로 한다. 들어보기로 한다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.427-431
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• 1986

3점 굽힘 시험편, 중앙균열 인장 시험편, 콤팩트 인장 시험편에 대한 J적분식을 하나의 일반화된 형태로 유도한다. 이 일반식은 Eftis와 Liebowitz에 의해 제안된 하중과 하중점 변위 사이의 관계와 Sumpter에 의한 탄성과 소성성분 J적분의 중첩개념을 이용함으로써 유도된다. 일반식에 포함된 .eta.계수를 위 3가지 시험편에 대해서 결정한다. 위 3가지 시험편에 대한 J적분의 최종식은 하중과 하중점 변위곡선 아래의 면적을 측정하지 않아도 되는 형태로 나타난다. 본 연구의 결과식은 Landes등에 의한 실험치와 비교하여 매우 잘 일치함을 보인다.

• Journal of Ocean Engineering and Technology
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• v.10 no.3
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• pp.3-13
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• 1996

An extensive research programme has been aimed at the effct of ship weight distribution on the ship responses applying ship hydroelasticity theory. In the previous works, consistent tendencies of the still-water and the wave bending moments. respectively, were found as the weight distribution was varied systematically. The paper is therefore concerned mainly with any correlation between still-water and wave bending moments with the variations of weight distribution. Although these bending moments share different features with each other, such a comparison of tendencies was plausible and informative. These and other matters for the future are discussed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.1
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• pp.18-23
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• 1985

In the fracture mechanics, the determination of the stress intensity factor value is vital for the prediction of a material fracture behavior. So many data concerning to the S.I.F. have been presented by many investigations to meet endless requrement. In this paper, the stress intensity factors of a sheet with an eccentrically inclined crack subjected to the pure bending moment were investigated theoretically by using of the complex mapping function to determine the Muskelishvili's comlex stress functions. Moreover, the theoretical value was compared with the result obtained from photoelastic esperiment. As a result, it was confirmed that both values coincided with satisfactorily within the margin of 2-3% devition; The results theoretically derived are right.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.285-288
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• 2007

In the recent years the using of low-density material such as high-strength Al alloy on the various industries is becoming light-weight. High strength and hollow Al alloy is good material for stiffness and recycling. Therefore the advanced manufacturing technology with Al alloy is continuously required in many industrial fields. In this study simplified hallow rectangular section of Al alloy is analyzed by FE analysis. Bending stress is affected punching and rotating of wing-die. The analysis of press bending is preformed at first. The elastic recovery value of component and stress distribution acting from the result of the bending angle of three types were obtained. The designed precesses were analyzed by the commercial FE code, Deform-3D. Forming dies for each process were designed and prototypes were manufactured by the verified forming process. Some of the important features of design parameters in the press bending were reviewed.