• 제목/요약/키워드: Micro-mechanical modeling

검색결과 130건 처리시간 0.025초

A study on the dynamic instabilities of a smart embedded micro-shell induced by a pulsating flow: A nonlocal piezoelastic approach

  • Atabakhshian, Vahid;Shooshtaria, Alireza
    • Advances in nano research
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    • 제9권3호
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    • pp.133-145
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    • 2020
  • In this study, nonlinear vibrations and dynamic instabilities of a smart embedded micro shell conveying varied fluid flow and subjected to the combined electro-thermo-mechanical loadings are investigated. With the aim of designing new hydraulic sensors and actuators, the piezoelectric materials are employed for the body and the effects of applying electric field on the stability of the system as well as the induced voltage due to the dynamic behavior of the system are studied. The nonlocal piezoelasticity theory and the nonlinear cylindrical shell model in conjunction with the energy approach are utilized to mathematically modeling of the structure. The fluid flow is assumed to be isentropic, incompressible and fully develop, and for more generality of the problem both steady and time dependent flow regimes are considered. The mathematical modeling of fluid flow is also carried out based on a scalar potential function, time mean Navier-Stokes equations and the theory of slip boundary condition. Employing the modified Lagrange equations for open systems, the nonlinear coupled governing equations of motion are achieved and solved via the state space problem; forth order numerical integration and Bolotin's method. In the numerical results, a comprehensive discussion is made on the dynamical instabilities of the system (such as divergence, flutter and parametric resonance). We found that applying positive electric potential field will improve the stability of the system as an actuator or vibration amplitude controller in the micro electro mechanical systems.

마이크로 엔드밀링 공정의 절삭계수 모델링 및 최적 공정설계 (Modeling of Cutting Parameters and Optimal Process Design in Micro End-milling Processes)

  • 이광조;정성종
    • 한국생산제조학회지
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    • 제18권3호
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    • pp.261-269
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    • 2009
  • Micro end-milling process is applied to fabricate precision mechanical parts cost-effectively. It is a complex and time-consuming job to select optimal process conditions with high productivity and quality. To improve the productivity and quality of precision mechanical parts, micro end-mill wear and cutting force characteristics should be studied carefully. In this paper, high speed machining experiments are studied to construct the optimum process design as well as the mathematical modeling of tool wear and cutting force related to cutting parameters in micro ball end-milling processes. Cutting force and wear characteristics under various cutting conditions are investigated through the condition monitoring system and the design of experiment. In order to construct the cutting database, mathematical models for the flank wear and cutting force gradient are derived from the response surface method. Optimal milling conditions are extracted from the developed experimental models.

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Fabrication and Modeling of Microlens Array by a Modified LIGA Process

  • Kim Dong Sung;Lee Hyun Sup;Yang Sang Sik;Lee Bong-Kee;Lee Sung-Keun;Kwon Tai Hun;Lee Seung S.
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2003년도 The Korea-Japan Plastics Processing Joint Seminar
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    • pp.7-13
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    • 2003
  • Microlens arrays were fabricated using a novel fabrication technology based on the exposure of a PMMA (Polymethylmethacrylate) sheet to deep X-rays and subsequent thermal treatment. X-ray irradiation causes the decrease of molecular weight of PMMA, which in turn decreases the glass transition temperature and consequently causes a net volume increase during the thermal cycle resulting in a swollen microlens. A new physical modeling and analyses for micro lens formation were presented according to experimental procedure. A simple analysis based on the new model is found to be capable of predicting the shapes of micro lens which depend on the thermal treatment. For the replication of micro lens arrays having various diameters with different foci on the same surface, the hot embossing and the microinjection molding processes has been successfully utilized with a mold insert that is fabricated by Ni-electroplating based on a PMMA microstructure of micro lenses. Fabricated microlenses showed good surface roughness with the order of 1nm.

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정밀소형회전기구의 마모해석모델에 관한 연구 (Development of Wear Analysis Model of Precision Small Rotating Device)

  • 여은구;조선형;이용신
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2003년도 춘계학술대회논문집
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    • pp.355-358
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    • 2003
  • Recently, micro forming process technology have been developed since the size of machine parts become the crucial factor for minimizing of products in general electronic products. Most small machine parts consist of gear and rotation axis and the wear by mechanical contact is known as the primary factor for life reduction of high precision machine part. Lots of studies for mechanical wear and friction have been reported and many researches of MEMS technology have been studied recently. But just few studies for wear of micro or milli sized machine part have teen implemented. In this research, the wear equation is suggested according to the contact shape of axial part in micro or milli sized machine part. And wear analysis model which can predict the magnitude of wear through this suggested equation with numerical analysis program.

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CNC 공작기계 스핀들 유닛의 5자유도 열변형 오차측정 및 모델링 기술 (Thermal Error Measurement and Modeling Techniques for the 5 Degree of Freedom(DOF) Spindle Unit Drifts in CNC Machine Tools)

  • 박희재;이석원;권혁동
    • 대한기계학회논문집A
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    • 제24권5호
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    • pp.1343-1351
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    • 2000
  • Thermally induced errors have been significant factors affecting the machine tool accuracy. In this paper, the spindle thermal error has been focused, where the 5 degree of freedom thermal error components are considered. An effective measurement system has been devised for the 5 DOF thermal errors, consisting of gap sensors and thermocouples around the micro-computer interfaced environment. Several thermal error modeling techniques are also implemented for the thermal error prediction: multiple linear regression, neural network and system identification methods, etc. The performance of the thermal error modeling techniques is evaluated and compared, giving the system identification method as the optimum model having the least deviation. The developed system for the thermal error measurement and modeling was practically applied to a CNC machining center, and the spindle thermal errors were effectively compensated around the micro computer-machine tool interfaced networks. The machine tool accuracy was improved about 4-5 times typically.

미세방전가공 중 발생하는 debris를 고려한 가공특성 연구 (Influence of Debris in Micro Electrical Discharge Machining Processes)

  • 국경훈;이희원;민병권;이상조
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2005년도 춘계학술대회 논문집
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    • pp.1244-1247
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    • 2005
  • The material removal mechanism of Electrical Discharge Machining (EDM) process has been studied for several decades. However, understanding of the material removal mechanism is still a difficult problem because the mechanism involves complicated physical phenomena including plasma. Especially, for a micro-EDM process, due to the influence of the debris that is generated during the machining process, quantitative modeling of EDM becomes more complex. To understand better the effects of the debris in the micro-EDM process experimentally, a new approach has been introduced in this study. Using a specially designed workpiece holder, the debris generated during the EDM with various process conditions has been collected. Then, using a simulated environment using micro-sized metal powders, the influence of the debris during the single EDM discharge has been observed. The effects of EDM process parameters on the debris size and product quality are discussed.

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변형 LIGA 공정을 통해 제작된 Microlens의 모델링 및 시뮬레이션 (Modeling and Simulation of Microlens Fabricated by Modified LIGA Process)

  • 김동성;이성근;양상식;권태헌;이승섭
    • 대한기계학회논문집A
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    • 제26권9호
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    • pp.1923-1930
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    • 2002
  • In this paper, we present modeling and simulation of microlens formation by means of a deep X-ray lithography followed by a thermal treatment of a PMMA (Polymethylmethacrylate) sheet. According to this modeling, X-ray irradiation causes the decrease of molecular weight of PMMA, which in turn decreases the glass transition temperature and consequently causes a net volume increase during the thermal cycle resulting in a swollen microlens. In this modeling, the free volume theory including the relaxation process during the cooling process was considered. The simulation results indicate that the modeling in this study is able to predict the fabricated microlens shapes and the variation pattern of the maximum heights of microlens which depends on the conditions of the thermal treatment. The prediction model could be applied to optimization of microlens fabrication process and to designing a micro mold insert for micromolding processes.

Crawling 방식을 이용한 관 탐사용 소형 로봇의 이동속도 해석 (Theoretical Velocity Analysis of Micro Robot Based on Crawling Locomotive Mechanism for Pipe Inspection Micro Robot)

  • 장기현;박현준;김병규
    • 대한기계학회논문집A
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    • 제32권8호
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    • pp.633-641
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    • 2008
  • Recently, the necessity for diagnosis and management of pipes has emerged as the issue due to contamination of water supply generated by corrosion of pipes. Although inspection has been performed with industrial endoscopes, the method has limits for full diagnosis of pipes due to the lack of working range. As a solution for this problem, many locomotive mechanisms for a micro robot with endoscope functions were proposed. In this paper, we analyze the locomotive mechanism of crawling robot proposed as locomotive device for pipe inspection. Based on a mechanical modeling of motor and micro robot inside small pipe, the theoretical formula for velocity is obtained. This derived theoretical formula is demonstrated the feasibility through the comparison with experimental result. Also, we could find the most important element influencing the moving velocity of micro robot when the robot operates in small pipe. Consequently, it is expected that this study can supply useful information to design of crawling robot to move in small pipe.

자기 부상 방식 미세 운동 기구의 동적 모델링 (Dynamic Modeling of an Fine Positioner Using Magnetic Levitation)

  • 정광석;백윤수
    • 대한기계학회논문집A
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    • 제24권5호
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    • pp.1166-1174
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    • 2000
  • In this paper, we introduce a positioner based on magnetic levitation to eliminate the friction which is the most severe effect to limit high resolution on the micro level. Differently from existing electromagnetic device, the proposed positioner consists of air core solenoid and permanent magnet. Although the combination produces small magnetic force, it is suitable for realizing micro motion repeatedly without the accumulation of error because there is no hysteresis caused by ferromagnetic materials, no eddy current loss, no flux saturation. First, the approximate modeling of stiffness and damping effects between the magnetic elements is made and verified experimentally. Then, we have formulated the dynamic equation of one d.o.f magnetic levitation positioner using linear perturbation method and discussed the necessity of optimization for the chief design parameters to maximize the stability performance.

진동에 의한 압전 마이크로 발전기의 모델링 및 해석 (Modeling And Analysis of a Piezoelectric Vibration-Induced Micro Power Generator)

  • 김준홍;박문수;이상호
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2007년도 춘계학술대회A
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    • pp.741-745
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    • 2007
  • Supplying power to microsystems that have no physical connection to the outside is difficult, and using batteries is not always appropriate. This paper discusses how to generate electricity from mechanical energy when vibrated in a cantilever beam. A model for the system predicts that the output power of the system is maximized when the mechanical damping in the system is minimized. Furthermore, to cover a wide frequency range and to be useful in a number of applications, a system of beams with different resonant frequencies has been designed and optimized. This information makes it possible to determine what design alternatives are feasible for the creation of a micro power supply for any specific application of MEMS.

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