• Composites Research
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• 제23권4호
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• pp.21-27
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• 2010

대부분의 구조물 파괴는 피로에 의해서 발생한다. 따라서 지금까지 모드 혼합비가 피로 특성에 어떤 영향을 미치는지에 대한 수많은 연구가 수행되어 오고 있다. 하지만 대부분의 연구가 금속/금속 계면이나 복합재료 층간 분리에 관한 연구이다. 따라서 본 연구에서는 이종재료인 복합재료/금속 계면의 피로 특성에 대한 기초 자료를 얻고자 하였다. 이를 위하여 복합재료와 탄소강을 동시 경화법을 이용하여 접합한 SLB(single leg bending) 시편을 이용하여 피로 실험을 수행하였다. 특히, 피로 특성에 모드 혼합비$(G_{II}/G_T)$가 어떠한 영향을 미치는지에 대해 알아보고자 하였다. 전체적으로 모드 II 하중 성분 이 많을수록 균열진전속도가 빨라진다는 결과를 얻었다.

• Steel and Composite Structures
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• 제17권3호
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• pp.339-358
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• 2014

Exodermic deck systems are new composite steel grid deck systems which have been used in various projects during the past decade. One of the eminent features of this system is considerable reduction in the structure weight compared to the ordinary reinforced concrete decks and also reduction in construction time by using precast Exodermic decks. In this study, dynamic properties of the Exodermic deck bridges with alternative perfobond shear connectors are investigated experimentally. In order to evaluate the dynamic properties of the decks, peak picking and Nyquist circle fit methods are employed. Frequencies obtained experimentally are in good agreement with the results of the finite-element solution, and the experimental results show that the first mode is the most effective mode among the obtained modes. The first four modes are the rigid translational motion modes, and the next two modes seem to be rigid rotational motion modes around a horizontal axis. From the 7th mode onwards, modes are flexible. The range of damping ratios is about 0.5%. Furthermore, the static behavior of the Exodermic decks under a static load applied at the center of the decks was investigated. Failure of the decks under positive bending was punching-shear. The bending strength of the decks under negative bending was about 50 percent of their strength under positive bending. In addition, the weight of an Exodermic deck is about 40% of that of an equivalent reinforced concrete slab.

• 한국철도학회논문집
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• 제15권5호
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• pp.423-428
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• 2012

철도차량의 속도가 증가함에 따라 레일 불균일에 의한 가진주파수의 상승으로 인하여 철도차량의 동특성을 고려한 승차감 예측기술이 중요해지고 있다. 철도차량의 동특성은 전산 모드해석과 더불어 시험적으로 검증되어야 한다. 본 연구에서는 철도차량 차체 굽힘모드 시험을 고찰하고, 이를 대체할 수 있는 방안을 제시하였다. 이를 위해 우선 차체 크기비를 반영한 평판 시편을 제적하고, 이를 기존 시험규격인 JIS E7105방법과 충격시험을 사용한 결과를 비교하여 충격시험의 타당성을 검증하였다. 또한 전산해석을 통하여 이를 재현하였다. 타당성이 검증된 결과를 바탕으로 현장 굽힘모드 시험을 유압가진 대신 충격시험으로 대체 가능성을 검토하였다.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.144-148
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• 2002

Influences of bending strain on the critical current (I$_{c}$) were investigated in Bi-2223 superconducting tapes at 77K. The effect of bending mode on the I$_{c}$ degradation behavior was discussed in viewpoints of test method, n-value and damage morphology. Especially, in this paper, we reported the I$_{c}$ behavior in Ag alloy/Bi-2223 multifilamentary super- conducting tapes under bending occurred within width x length plane of the tape which was called as a hard bending.nding.

• 한국정밀공학회지
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• 제15권12호
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• pp.188-193
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• 1998

This paper describes static and dynamic weak point analysis of spindle systems to eliminate high concentrated bending point on spindle and improve total stiffness of spindle systems. The weak point analysis is based on the evaluation of bending curves of spindles. For static weak point analysis the bending curve is derived from static deflection curve and for dynamic weak point analysis it is derived from the mode shape curves in consideration of the transfer function at exciting point. The validity of the weak point search methodology is verified by comparison of the static deflection, the natural frequency and the dynamic compliance between the original and the improved spindle.

• Advances in nano research
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• 제9권2호
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• pp.91-104
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• 2020

The bending, stability (buckling) and vibration response of nano sized beams is presented in this study based on the Eringen's nonlocal elasticity theory in conjunction with the Euler-Bernoulli beam theory. For this purpose, the bending, buckling and vibration problem of Euler-Bernoulli nanobeams are developed and solved on the basis of nonlocal elasticity theory. The effects of various parameters such as nonlocal parameter e₀a, length of beam L, mode number n, distributed load q and cross-section on the bending, buckling and vibration behaviors of carbon nanotubes idealized as Euler-Bernoulli nanobeam is investigated. The transverse deflections, maximum transverse deflections, vibrational frequency and buckling load values of carbon nanotubes are given in tables and graphs.

• Structural Engineering and Mechanics
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• 제62권5호
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• pp.577-585
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• 2017

To study the mechanical performances of prestressed steel-concrete composite box beam under combination of bending-shear-torsion, nine composite beams with different ratio of torsion to bending were designed. Torsion was applied to the free end of the beam with jacks controlled accurately with peripherals, as well as concentrated force on the mid-span with jacks. Based on experimental data and relative theories, mechanical properties of composite beams were analyzed, including torsional angle, deformation and failure patterns. The results showed that under certain ratio of torsion to bending, cracking and ultimate torsion increased and reached to its maximum at the ratio of 2. Three phases of process is also discussed, as well as the conditions of each failure mode.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 D
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• pp.2152-2154
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• 2004

A robust bending frequency tracker is proposed to design the adaptive notch filter which removes the time-varying missile structural mode from the sensor measurements. To design the bending frequency tracker, firstly, the signal model is derived from the input-output relationship of Nehorai notch filter structure. Also, the time-varying nature of the bending frequency is modelled as the norm-bounded uncertainty. Based on the uncertain signal model, it is shown that the design problem of robust bending frequency tracker can be casted into that of adaptive robust $H_{\infty}$ filter or equivalently robust LMS filter.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1283-1288
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• 2008

The FPCB is used as the important component of the sliding mechanism of mobile phones. FPCB have been used as jumper cables(fixed wiring) in various types of circuits because of their flexibility and bending property. The dominant failure mode of the FPCB is open that was caused by fatigue. The fatigue is repeated whenever the sliding is open, so it is a mainly cause of FPCB fatigue. We examined the bending-fatigue lifetime of FPCB. we focused on observing the contact resistance degradation of FPCB of mobile phones according to different test condition of bending strain. As a result, it has proved that lifetime decreased by increasing bending strain.

• Architectural research
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• 제23권1호
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• pp.11-17
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• 2021

A concrete-filled circular steel tube beam was fabricated, and a bending test was performed to analyze its failure modes, displacement ductility, bending-shear strength, and load-central deflection relationship. For the bending test, the installation position of the shape memory alloy (SMA) inside and outside the double-skin steel tube was used, and the rebar installation position, the concrete strength, the mixing of fibers, and the inner-outer diameter ratio as the main parameters. The test results showed that the installation positions of the reinforcements inside and outside the double-skin steel tube and the inner-outer diameter ratio of the steel tube affected the ductility, maximum load, and failure mode. In general, the specimen made of general concrete with SMA installed outside and inside (OI) the double-skin steel tube showed the best results.