• Journal of Welding and Joining
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• 제16권2호
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• pp.40-47
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• 1998

In the present study, depressions of the GMA weld pool due to the impact of droplet are numerically investigated. The numerical simulation is conducted on the basis of the Navier-Stokes equation and the volume of fluid(VOF) functions. The kinetic energy of transferring droplet makes a depression of the weld pool surface. The surface active element affects the depression of the weld pool. The droplets transferred efficiently to the bottom of the weld pool, along with electromagnetic force make the finger shape penetration at the high current GMAW.

• Smart Structures and Systems
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• 제20권6호
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• pp.657-668
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• 2017

In this research, an active vibration suppression of a smart beam having piezoelectric sensor and actuators is investigated by designing separate controllers comprising a linear quadratic regulator and a neural network. Firstly, design of a smart beam which consists of a cantilever aluminum beam with surface bonded piezoelectric patches and a designed mechanism having a micro servomotor with a mass attached arm for obtaining variations in the frequency response function are presented. Secondly, the frequency response functions of the smart beam are investigated experimentally by using different piezoelectric patch combinations and the analytical models of the smart beam around its first resonance frequency region for various servomotor arm angle configurations are obtained. Then, a linear quadratic regulator controller is designed and used to simulate the suppression of free and forced vibrations which are performed both in time and frequency domain. In parallel to simulations, experiments are conducted to observe the closed loop behavior of the smart beam and the results are compared as well. Finally, active vibration suppression of the smart beam is investigated by using a linear controller with a neural network based adaptive element which is designed for the purpose of overcoming the undesired consequences due to variations in the real system.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.834-839
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• 2004

In this paper, we have studied on the active vibration control of an automotive roof in passenger car's structure using piezoelectric material as the actuator and sensor attached on the surface of the automotive roof, As a control algorithm, negative velocity feedback control method is used in the study and the position of the sensor is almost attached on the nearest position of maximum normal stresses occurring while the roof is vibrating due to disturbance or exciting, Also, the actuator is attached on the other side mostly collocated to the sensor. The optimum positions have the maximum stresses of the roof which have been found in the result of the finite element analysis using Nastran software, As the fundamental experiments, a beam and plate have also been implemented to verify the performance of vibration suppression. Finally the experiment of the roof has been carried out and The roof experiment has just given a possibility to an active vibration control of the automotive structure still not applied for passenger cars.

• Carbon letters
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• 제12권3호
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• pp.180-183
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• 2011

Li metal is accepted as a good counter electrode for electrochemical impedance spectroscopy (EIS) as the active material in Li-ion and Li-ion polymer batteries. We examined the existence of signal noise from a Li-metal counter quantitatively as a preliminary study. We suggest an electrochemical cell with one switchable electrode to obtain the exact impedance signal of active materials. To verify the effectiveness of the switchable electrode, EIS measurements of the solid electrolyte interphase (SEI) before severe $Li^+$ intercalation to SFG6 graphite (at > ca. 0.25 V vs. Li/$Li^+$) were taken. As a result, the EIS spectra without the signal of Li metal were obtained and analyzed successfully for the following parameters i) $Li^+$ conduction in the electrolyte, ii) the geometric resistance and constant phase element of the electrode (insensitive to the voltage), iii) the interfacial behavior of the SEI related to the $Li^+$ transfer and residence throughout the near-surface (sensitive to voltage), and iv) the term reflecting the differential limiting capacitance of $Li^+$ in the graphite lattice.

• 한국산업융합학회 논문집
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• 제24권1호
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• pp.31-43
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• 2021

In this study, approximate design optimization using various meta-models was performed for the structural design of active type deck support frame. The active type deck support frame was newly developed to facilitate both transportation and installation of 20,000 ton class offshore plant topside. Structural analysis was carried out using the finite element method to evaluate the strength performance of the active type deck support frame in its initial design stage. In the structural analysis, the strength performances were evaluated for various design load conditions that were regulated in ship classification organization. The approximate optimum design problem based on meta-model was formulated such that thickness sizing variables of main structure members were determined by achieving the minimum weight of the active type deck support frame subject to the strength performance constraints. The meta-models used in the approximate design optimization were response surface method, Kriging model, and Chebyshev orthogonal polynomials. The results from approximate design optimization were compared to actual non-approximate design optimization. The Chebyshev orthogonal polynomials among the meta-models used in the approximate design optimization represented the most pertinent optimum design results for the structure design of the active type deck support frame.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.604-607
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• 2003

Recently, hybrid concrete structures such as a concrete-filled steel tubular(CFT), a steel reinforced concrete(SRC) and a composite material are popular in structure applications. They also have merit of high strength, high ductility, and large energy absorption capacity. But the analysis of hybrid concrete structures is very difficult owing to the complex behavior of concrete under passive confinement. This paper has analyzed CFT, which receives passive confinement using Tri-Surface concrete model for three dimension finite element analysis. By the result of that, the proposed model was properly forecasted a concrete behavior that receives passive restraint as well as non-linear analysis of concrete which receive uniaxial stress and high active confinement of 400Mpa. If the model through the steady study is set up especially on the factor of concrete under passive confinement, the proposed concrete model will be surely useful for analysis of the hybrid concrete structures.

• Journal of Welding and Joining
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• 제15권3호
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• pp.65-78
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• 1997

The effect of $O_2$and Al contents and the variation of welding parameters such as arc currents, welding speed on the weld penetration was investigated. Examination of weld penetration using GTAW was accomplished in the ferritic STS410L and austenitic STS304. Good penetration could be controlled by the variation of $O_2$ and Al contents in STS304. However, influences of $O_2$ and Al contents on the ferritic STS410L are far less than those on the austenitic STS304. Welding parameters should be considered first before controlling $O_2$ and Al contents for a good penetration in ferritic STS410L. In the simulation study under the stationary heat sources, the results of simulation and experiment have a similar tendency.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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• pp.478-485
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• 2002

The shape memory alloys (SMAs) are often used in smart materials and structures as the active components. Their ability to provide a high recovery force and a large displacement has been used in many applications. In this paper the radial displacement of an externally pressurized elliptic composite cylinder where SMA liner or strips actuators are bonded on its inner or outer surface is investigated numerically. The elliptic composite cylinders consisting of an inlet duct system with SMAs are designed and analyzed to determine the feasibility of such a system for the removal of stiffeners from an externally pressurized duct of an aircraft inlet. The deformations caused by prestrained SMAs placed on either surface of an elliptic composite cylinder are studied when activated. The externally pressurized elliptic composite cylinders with the SMA actuators were analyzed using the 3-D finite element method incorporated with 3-D SMA behaviors. The results show that the role of stiffeners may be switched by the activated light SMA actuators.

• 한국진공학회지
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• 제4권S2호
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• pp.49-57
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• 1995

At present the processes of boronizing have been mostly studied in a plasma from gaseous compounds containing the impregnating element and are in an industrial use. These have been investigated by a variety of works in a glow discharge with different mixture ratios of $B_2H_6$ and $H_2$ as well as $BCl_3$ and $H_2$. The active atomosphere has been diluted by Ar or some other inert gas in order to enhance control of boron potential and to reduce the ignition voltage of the glow discharge. The Control of gaseous atomosphere is essential to a boride layer in plamsa boronizing treatment. The boride formation is required to make the workpiece surface saturated with boron content. The present study considers the efficiency of plasma boronizing reactions and the morphology of boride layer under various plasma conditions

• 대한기계학회논문집 C: 기술과 교육
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• 제3권3호
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• pp.183-191
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• 2015

본 논문에서는 헬리콥터 로터 시스템의 진동과 소음을 저감시키기 위해 개발이 진행 중인 능동거니플랩(AGF, Active Gurney Flap)에 대해 유한요소법을 이용하여 수행된 동특성 해석결과를 소개하였다. 거니플랩은 평판의 형태로 블레이드 하부 표면에 수직인 방향으로 전개되며, 블레이드 뒷전(T/E, Trailing Edge) 부위에 장착된다. 거니플랩 조립체는 전기모터와 L-형 링키지 및 플랩 등의 부품들로 구성되어 블레이드 내부에 장착되며, 고정프레임에서의 진동 성분들을 감소시키기 위해 3~5/rev 범위로 능동적인 제어가 필요하다. 따라서 외연적 시간적분법을 통해 로터 회전에 의한 원심력과 제어입력이 적용되고 있는 상황에서 거니플랩의 동적 응답특성을 분석하였으며, 해석 결과를 통해 거니플랩의 하향변위 요구도를 만족시킬 수 있음을 확인하였다.