• Proceedings of the KSME Conference
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• 2005.11a
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• pp.152.2-152.2
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• 2005

• The Korean Journal of Rheology
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• v.3 no.2
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• pp.156-165
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• 1991

폴리비닐리덴플루오라이드 바이모프 외팔보(poly(vinylidene fluoride) bimorph cantilever beam)의 진동을 기술하는 수학적 모형을 세우고 실험으로 그모형의 타당성을 고 찰하였다. 여러 전압의 교류전류에 대해 여러 길이의 외팔보의 주파수응답을 측정하였고 여 러 전압의 직류전류에 대해 여러 길이의 외팔보의 처짐을 측정하였다. 실험으로부터 이 외 팔보의 진동은 점성감쇠보다는 구조감쇠로 기술하는 것이 더 타덩하고 외팔보가 전기장에 대해 damping factor가 일정해야 하나 각각의 normal mode에 대해 다른 damping factor로 수정하여 계산한이론치가 실험과 더 일치하였다. 공명주파수의 공명진폭을 예측할수 있고 넓은 입력주파수 영역에 대한 외팔보의 응답을 기술 할수 있으며 진동하는 외팔보는 모든위 치에서의 진폭을 기술할수 있다는 점에서 여기서의 모형은 Toda와 Smits의 모형들보다 우 수하다고 볼수 있다.

• Journal of Sensor Science and Technology
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• v.29 no.2
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• pp.100-104
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• 2020

Thus far, several in vivo biosensing platforms have been proposed to measure the mechanical contractility of cultured cardiomyocytes. However, the low sensitivity and screening rate of the developed sensors severely limit their practical applications. In addition, intensive research and development in cardiovascular disease demand a high-throughput drug-screening platform based on biomimetic engineering. To overcome the drawbacks of the current state-of-the-art methods, we propose a high-throughput drug-screening platform based on 16 functional high-sensitivity well plates. The proposed system simulates the physiological accuracy of the heart function in an in vitro environment. We fabricated 64 cantilevers using highly flexible and optically transparent silicone rubber and placed in 16 independent wells. Nanogrooves were imprinted on the surface of the cantilever to promote cell alignment and maturation. The adverse effects of the cardiovascular drugs on the cultured cardiomyocytes were systematically investigated. The 64 cantilevers demonstrated a highly reliable and reproducible mechanical contractility of the drug-treated cardiomyocytes. Real-time high-throughput screening and simultaneous evaluation of the cardiomyocyte mechanical contractility under multiple drugs verified that the proposed system could be used as an efficient drugtoxicity test platform.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.2
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• pp.7-12
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• 2000

Copper-based leadframe sheets were oxidized in a black-oxide forming solution, and molded with epoxy molding compound (EMC) to form sandwiched double-cantilever beam (SDCB) specimens. The adhesion strength of leadframe/EMC interface was measured in terms of fracture toughness by using SDCB specimens and the fracture surfaces were analyzed by various equipments such as glancing-angle XRD, AFM, and SEM. Results showed that three types of failure paths, which were closely related to the surface condition of leadframes before molding.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.295-298
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• 2001

This paper presents mechanical properties and weatherability of FRP pole used for a distribution line about high strength and good insulation properties. The experiment strength obtained in cantilever beam test are comparable to ES standards. The environmental factors, such as elevated temperatures, high humidity, and corrosive fluids, and ultraviolet(UV) rays, influence on the performance of Polymeric matrix composite.

• Steel and Composite Structures
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• v.45 no.3
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• pp.409-423
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• 2022

Nowadays, there is a high demand for great structural implementation and multifunctionality with excellent mechanical properties. The porous structures reinforced by graphene platelets (GPLs) having valuable properties, such as heat resistance, lightweight, and excellent energy absorption, have been considerably used in different engineering implementations. However, stiffness of porous structures reduces significantly, due to the internal cavities, by adding GPLs into porous medium, effective mechanical properties of the porous structure considerably enhance. This paper is relating to vibration analysis of fluidconveying cantilever porous graphene platelet reinforced (GPLR) pipe with fractional viscoelastic model resting on foundations. A dynamical model of cantilever porous GPLR pipes conveying fluid and resting on a foundation is proposed, and the vibration, natural frequencies and primary resonant of such a system are explored. The pipe body is considered to be composed of GPLR viscoelastic polymeric pipe with porosity in which Halpin-Tsai scheme in conjunction with the fractional viscoelastic model is used to govern the construction relation of nanocomposite pipe. Three different porosity distributions through the pipe thickness are introduced. The harmonic concentrated force is also applied to the pipe and the excitation frequency is close to the first natural frequency. The governing equation for transverse motions of the pipe is derived by the Hamilton principle and then discretized by the Galerkin procedure. In order to obtain the frequency-response equation, the differential equation is solved with the assumption of small displacement, damping coefficient, and excitation amplitude by the multiple scale method. A parametric sensitivity analysis is carried out to reveal the influence of different parameters, such as nanocomposite pipe properties, fluid velocity and nonlinear viscoelastic foundation coefficients, on the primary resonance and linear natural frequency. Results indicate that the GPLs weight fraction porosity coefficient, fractional derivative order and the retardation time have substantial influences on the dynamic response of the system.

• Steel and Composite Structures
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• v.50 no.2
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• pp.201-216
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• 2024

This paper is motivated by the lack of studies relating to vibration and nonlinear resonance of fluid-conveying cantilever porous GPLR pipes with fractional viscoelastic model resting on nonlinear foundations. A dynamical model of cantilever porous Graphene Platelet Reinforced (GPLR) pipes conveying fluid and resting on nonlinear foundation is proposed, and the vibration, natural frequencies and primary resonant of such system are explored. The pipe body is considered to be composed of GPLR viscoelastic polymeric pipe with porosity in which Halpin-Tsai scheme in conjunction with fractional viscoelastic model is used to govern the construction relation of the nanocomposite pipe. Three different porosity distributions through the pipe thickness are introduced. The harmonic concentrated force is also applied on pipe and excitation frequency is close to the first natural frequency. The governing equation for transverse motion of the pipe is derived by the Hamilton principle and then discretized by the Galerkin procedure. In order to obtain the frequency-response equation, the differential equation is solved with the assumption of small displacement, damping coefficient, and excitation amplitude by the multiple scale method. A parametric sensitivity analysis is carried out to reveal the influence of different parameters, such as nanocomposite pipe properties, fluid velocity and nonlinear viscoelastic foundation coefficients, on the primary resonance and linear natural frequency. Results indicate that the GPLs weight fraction porosity coefficient, fractional derivative order and the retardation time have substantial influences on the dynamic response of the system.

• Composites Research
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• v.24 no.5
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• pp.39-43
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• 2011

For the last twenty years, nanocomposites composed of polymer matrices reinforced with carbon nanotubes (CNTs) have been an active research area. Also, the polymeric nanocomposites reinforced with CNTs are being investigated to be used matrices of carbon fiber composites. Carbon tiber composites have achieved advanced properties in the direction of carbon fibers due to enhanced carbon fiber properties. However, the matrix dominated properties need to be improved further to fully utilize the advanced carbon fiber properties. In particular, delamination is a typical and critical reason for fracture of carbon fiber composites. Mode I fracture toughness test which is also often called double cantilever beam (DCB) test shows the resistance to delamination of carbon fiber composites and this test is performed on carbon fiber composite samples incorporated with carbon nanotubes functionalized with various functional groups. The specimens with mat-like CNT layers showed the increased fracture toughness by 10.6%.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.142-148
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• 2012

This study presents the assessment results of adhesive properties on the interface between a silicon wafer and nano-scale polymer thin film pattern through UAFM images by using the contact resonance frequency of the cantilever. For the experiment, we varied surface treatment processes for the silicon wafer and fabricated a 300nm polymer thin film pattern through lithography. Images from the optical microscope were used to compare the produced test specimens for adhesive condition and the critical load value from the nano scratch test was used to verify the adhesive condition of the nano pattern. Each test specimen resulted in a $1{\mu}m{\times}1{\mu}m$ surface image and subsurface adhesive image. Adhesive condition was evaluated by image contrast differences on the interface according to the changing amplitudes and phases of contact resonance frequency.

• KSTLE International Journal
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• v.6 no.2
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• pp.33-38
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• 2005

Submicron-scale patterns made of polymethyl methacrylate (PMMA) were fabricated on silicon-wafer using a capillarity-directed soft lithographic technique. Polyurethane acrylate (PUA) stamps (Master molds) were used to fabricate the patterns. Patterns with three different aspect ratios were fabricated by varying the holding time. The patterns fabricated were the negative replica of the master mold. The patterns so obtained were investigated for their adhesion and friction properties at nano-scale using AFM. Friction tests were conducted in the range of 0-80 nN. Glass (Borosilicate) balls of diameter 1.25 mm mounted on cantilever (Contact Mode type NPS) were used as tips. Further, micro-friction tests were performed using a ball-on-flat type micro-tribe tester, under reciprocating motion, using a soda lime ball (1 mm diameter) under a normal load of 3,000 mN. All experiments were conducted at ambient temperature ($24{\pm}1^{\circ}C$) and relative humidity ($45{\pm}5\%$). Results showed that the patterned samples exhibited superior tribological properties when compared to the silicon wafer and non-patterned sample (PMMA thin film) both at the nano and micro-scales, owing to their increased hydrophobicity and reduced real area of contact. In the case of patterns it was observed that their morphology (shape factor and size factor) was decisive in defining the real area of contact.