• 대한기계학회논문집A
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• 제40권1호
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• pp.53-63
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• 2016

자동차 주행 중 도로면으로부터 차량 바퀴에 전달되는 동하중을 측정하기 위해 휠 동력계가 사용된다. 본 논문에서는 전단 변형과 굽힘 변형을 이용한 두 가지 타입의 6축 휠 동력계를 설계하고 비교 평가하였다. 유한요소해석을 이용하여 휠 동력계 기본 구조에 대한 전단 변형 거동과 굽힘 변형 거동을 분석하였으며 이로부터 전단형 휠 동력계와 굽힘형 휠 동력계를 설계하였다. 변형률 해석을 반복 수행하여 각 하중에 대한 출력변형률이 미리 결정된 비슷한 값이 되도록 하고 상호간섭 변형률이 최소화 되도록 설계를 수정하고 브리지 회로를 구성하였다. 전단형 휠 동력계는 균일한 변형률 분포를 얻을 수 있어 제작시 안정된 특성치를 얻을 수 있는 반면에, 굽힘형 휠 동력계는 각 하중에 대한 출력 변형률 값이 더 일정하여 균일한 감도의 좋은 성능을 얻을 수 있을 것으로 예측된다.

• 대한기계학회논문집A
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• 제34권3호
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• pp.341-346
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• 2010

이종 접합재($\beta-Si_3N_4/S45C$)의 굽힘강도와 인장강도에 미치는 시험편 형상의 영향을 정량적으로 평가하였다. 평균 굽힘강도와 평균 인장강도는 원형단면 시험편이 4각형 단면 시험편보다 약간 높았다. 또한, 초음파(AE)를 이용하여 균열발생응력을 성공적으로 측정할 수 있었으며, 균열발생응력은 굽힘강도의 60~80% 이었다. 아울러, 세라믹측 접합계면 근처의 잔류응력 측정을 굽힘강도 시험전에 X선 회절법에 의해 실시하였으며, 굽힘강도와 균열발생응력은 잔류응력 증가와 더불어 감소하였다. 마지막으로 인장시험에서 굽힘변형률 성분의 영향을 평가하였으며, 인장강도는 굽힘변형률 성분의 증가와 더불어 감소하고 굽힘강도의 약 80%에 해당되었다.

• International Journal of Korean Welding Society
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• 제4권1호
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• pp.46-52
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• 2004

To combine the mechanical advantages of ceramics with those of metals, one often uses both materials within one composite component. But, as known, they have different material properties and fracture behaviors. In this study, a four-point bending test is carried out on $Si_3N_4$ joined to ANSI 304L stainless steel with a Ti-Ag-Cu filler and a Cu interlayer at room temperature to evaluate their longitudinal strain behaviors. And, to detect localized strain, a couple of strain gages are pasted near the joint interfaces of the ceramic and metal sides. The normal strain rates are varied from $3.33{\times}10^5$ to $3.33{\times}10^{-1}s^{-1}$ Within this range, the experimental results showed that the four-point bending strength and the deflection of the interlayer increased with increasing the strain rate.

• 한국정밀공학회지
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• 제16권3호통권96호
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• pp.222-232
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• 1999

This paper describes the development of a precision 3-component load cell with plate beams which may be used for measuring forces Fx, Fy and moment Mz simultaneously in industry. We have derived equations to predict the bending strains on the surface of the beams under forces or moment. We have also determined the attachment location of strain gages of each sensor and fabricated 3-component load cell. To evaluate the rated strain and interference error of each sensor, we have carried out characteristic test of precision 3-component load cell. It reveals that the rated strain calculated from the derived equations are good agreement with the results from Finite Element Method analysis.

• 한국정밀공학회지
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• 제15권8호
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• pp.109-115
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• 1998

This paper describes the development of a 6-component load cell with plate beams which may be used to measure forces Fx, Fy, Fz and moments Mx, My, Mz simultaneously in industry. We have analyzed the bending strains on the surface of the beams under forces or moments by using Finite Element Method and designed the sensing elements of 6-component load cell. We have also determined the attachment location of strain gages of each load cell and fabricated 6-component load cell. To evaluate the rated strain and interference error of each load cell, we have carried out characteristic test of 6-component load cell.

• 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.

• International Journal of Precision Engineering and Manufacturing
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• 제1권1호
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• pp.22-32
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• 2000

This paper describes the development of a precision 3-component load cell with plate beams which may be used for measuring forces Fx, Fy and moment Mz simultaneously in industry. The equations to predict the bending strains on the surface of the beams under forces or moment are derived, the attachment location of strain gages of each sensor is determined, and 3-component load cell is carried out. It reveals that the rated strain calculated from the derived equations are good agreement with the results from Finite Element Method analysis.

• 반도체디스플레이기술학회지
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• 제20권4호
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• pp.49-54
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• 2021

The display industry is transitioning from traditional rigid products such as flat panel displays to flexible or wearable ones designed to be folded or rolled. Accordingly, colorless and optically transparent polyimide (CPI) films are one of the prime candidates to substitute traditional cover glass as a passivation layer to accommodate product flexibility. However, CPI films subjected to repetitive pure bending loads inevitably entail an accumulation of residual strain that can eventually cause wrinkles or delamination in the underlying component after a certain number of static and cyclic loading. The purpose of this study is to establish an experimental method to systematically evaluate the bending residual strain of CPI films. Films were monotonically and cyclically wrapped on mandrels of various diameters to ensure a constant strain in each. After unwrapping the wound CPI film, the residual radius of curvature remaining on the film was measured and converted into residual strain. The critical radius of curvature at which residual strain does not remain was about 5 mm, and the residual strain decreased in proportion to the log time. It is expected that flexible displays can be reliably designed using the data between the applied bending strain and the residual strain.

• Journal of Mechanical Science and Technology
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• 제16권9호
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• pp.1078-1083
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• 2002

Ceramics are significantly used in many industrial applications due to their excellent mechanical and thermal properties such as high temperature strength, low density, high hardness, low thermal expansion, and good corrosion resistive properties, while their disadvantages are brittleness, poor formability and high manufacturing cost. To combine advantages of ceramics with those of metals, they are often used together as one composite component, which necessiates reliable joining methods between metal and ceramic. Direct brazing using an active filler metal has been found to be a reliable and simple technique, producing strong and reliable joints. In this study, the fracture characteristics of Si$_3$N$_4$ ceramic joined to ANSI 304L stainless steel with a Ti-Ag-Cu filler and a Cu (0.25-0.3 mm) interlayer are investigated as a function of strain rate and temperature. In order to evaluate a local strain a couple of strain gages are pasted at the ceramic and metal sides near joint interface. As a result the 4-point bending strength and the deflection of interlayer increased at room temperature with increasing strain rate. However bending strength decreased with temperature while deflection of interlayer was almost same. The fracture shapes were classified into three groups ; cracks grow into the metal-brazing filler line, the ceramic-brazing filler line or the ceramic inside.

• 한국재료학회지
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• 제28권11호
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• pp.671-679
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• 2018

Finite element analyses are carried out to understand the piezoelectric behaviors of ZnO nanowires. Three different types of ZnO nanowires, with aspect ratios of 1:2. 1:31, and 1:57, are analyzed for uniaxial compression, pure bending, and buckling. Under the uniaxial compression with a strain of $1.0{\times}10^{-4}$ as the reference state, it is predicted that all three types of nanowires develop the same magnitude of the piezoelectric fields, which suggests that longer nanowires exhibit higher piezoelectric potential. However, this prediction is not in agreement with the experimental results previously reported in the literature. Such discrepancy is understood when the piezoelectric behaviors under bending and buckling are considered. When only the strain field due to bending is present in bending or buckling, the antisymmetric nature of the through-thickness stain distribution indicates that two piezoelectric fields, the same in magnitude and opposite in sign, develop along the thickness direction, which cancels each other out, resulting in a zero net piezoelectric field. Once additional strain contribution due to axial deformation is superposed on the bending, such field cancelling is compensated for due to the axial component of the piezoelectric field. Such numerical predictions seem to explain the reported experimental results while providing a guideline for the design of nanowire-based piezoelectric devices.