• International Journal of Automotive Technology
• /
• 제6권2호
• /
• pp.149-159
• /
• 2005

A full nonlinear finite element P185/70Rl4 passenger car radial-ply tire model was developed and run on a 1.7-meter-diameter spinning test drum/cleat model at a constant speed of 50 km/h in order to investigate the tire transient response characteristics, i.e. the tire in-plane free vibration modes transmissibility. The virtual tire/drum finite element model was constructed and tested using the nonlinear finite element analysis software, PAM-SHOCK, a nonlinear finite element analysis code. The tire model was constructed in extreme detail with three-dimensional solid, layered membrane, and beam finite elements, incorporating over 18,000 nodes and 24 different types of materials. The reaction forces of the tire axle in vertical (Z axis) and longitudinal (X axis) directions were recorded when the tire rolled over a cleat on the drum, and then the FFT algorithm was applied to examine the transient response information in the frequency domain. The result showed that this PI 85/70Rl4 tire has clear peaks of 84 and 45 Hz transmissibility in the vertical and longitudinal directions. This result was validated against more than 10 previous studies by either theoretical or experimental approaches and showed excellent agreement. The tire's post-impact response was also investigated to verify the numerical convergence and computational stability of this FEA tire model and simulation strategy, the extraordinarily stable scenario was confirmed. The tire in-plane free vibration modes transmissibility was successfully detected. This approach was never before attempted in investigations of tire in-plane free vibration modes transmission phenomena; this work is believed to be the first of its kind.

• Composites Research
• /
• 제15권1호
• /
• pp.1-8
• /
• 2002

본 연구에서는 실제 구조형상의 사각형 상자형 날개와 전투기 날개에 대하여 구조재를 표피(skin)부분은 복합재료로 대체하고, 나머지 스파(spar)와 리브(rib)는 알루미늄으로 하여 플러터 해석을 수행하였다. MS/PATRAN을 이용하여 실제 날개 구조에 근사한 3차인 유한 요소 모델이 구축되었고, MSC/NASTRAN을 이용하여 고유진동 해석이 수행되었다. 유한 요소는 멤브레인(membrane)요소, 1차원 막대(rod)요소, 전단패널(shear panel)요소를 사용하였다. 복합재료의 적층은 실제적인 적층각을 이용하여 다양하게 변화시켜 해석하였다. 아음속 영역에서 비정상 공력 해석을 위하여 주파수 영역에서의 선형 공기력 이론인 DLM코드가 적용되었고, 주파수 영역 공탄성 지배방정식의 해법으로 V-g방법 및 p-k방법이 적응되었다.

• 음성과학
• /
• 제5권1호
• /
• pp.167-179
• /
• 1999

The hearing mechanism is a complicated system. Sound is generated by a source that sends out air pressure or power. The pressure or power makes the sound waves. These waves reach the eardrum, or tympanic membrane, which vibrates at a rate and magnitude proportional to the nature of the sound waves. The tympanic membrane transforms this vibration into the mechanical energy in the middle ear, which in turn converts it to the hydraulic energy in the fluid of the inner ear. The hydraulic energy stimulates the sensory cells of the inner ear which send neuroelectrical impulses to the central auditory nervous system. The passive perception of auditory information starts just here. The listener gives attention to the speech sound, differentiates the sound from background noise, and integrates his experience with similar sounds. The listener then puts all of these aspects of audition into the context of the moment to identify the nature of sound. This has a major role in human communication. This paper provides an overview of the nature and characteristics of sound, the structure and function of the auditory system, and the way in which sound is processed by the auditory system.

• 한국산학기술학회논문지
• /
• 제9권4호
• /
• pp.1043-1049
• /
• 2008

본 논문에서는 Navier 방법을 이용한 점진기능재료 판의 정적 응답과 고유진동수 그리고 좌굴하중을 연구하였다. S 형상 함수를 이용한 세라믹과 금속의 체적요소의 변화에 따른 점진기능재료 판의 고유치 문제를 연구하였다. 점진기능재료 판의 면내 강성, 휨 강성 및 전단 강성의 수식은 등질 요소보다 복잡한 재료의 성질들로 결합되어 있다. 본 연구의 결과를 검증하기 위해 고전적 이론에 의한 직사각형 판의 결과를 제시하였다. 적층복합 구조 및 S 형상 점진기능재료 구조의 다양한 예제를 제시하였다. 해석결과는 참고문헌의 결고들과 잘 일치함을 알 수 있었다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2008년도 춘계학술대회논문집
• /
• pp.294-298
• /
• 2008

The ionic polymer-metal composite actuators with selectively grown multiple electrodes were developed to mimic the swimming locomotion of a fish. The developed method is based on combining electroplating with the electroless chemical reduction using the patterned mask. The advantages of this fabrication method are that the initial compositing between the polymer and platinum particles can be assured by the chemical reduction method, and the thickness of each electrode can be controlled easily and rapidly by electroplating. By using the fabricated actuator with a multiple degree of freedom, the oscillatory wave of the flexible membrane actuator was generated and a twisting motion was also realized to verify the possibility of mimicking the fish-like locomotion. The frequency response function was analyzed to investigate the natural frequency and the damping factor by a mechanical shaker and direct electrical excitation through the swept-sine method. Present results show that this novel method can be a promising technique to easily pattern each of multiple electrodes and to implement the biomimetic motion of the polymer actuators with good mechanical bending performance.

• Structural Engineering and Mechanics
• /
• 제60권1호
• /
• pp.111-130
• /
• 2016

Two new elements with six degrees of freedom are proposed by applying the equilibrium conditions and strain-displacement equations. The first element is formulated for the infinite ratio of beam radius to thickness. In the second one, theory of the thick beam is used. Advantage of these elements is that by utilizing only one element, the exact solution will be obtained. Due to incorporating equilibrium conditions in the presented formulations, both proposed elements gave the precise internal forces. By solving some numerical tests, the high performance of the recommended formulations and also, interaction effects of the bending and axial forces will be demonstrated. While the second element has less error than the first one in thick regimes, the first element can be used for all regimes due to simplicity and good convergence. Based on static responses, it can be deduced that the first element is efficient for all the range of structural characteristics. The free vibration analysis will be performed using the first element. The results of static and dynamic tests show no deficiency, such as, shear and membrane locking and excessive stiff structural behavior.

• 한국정밀공학회지
• /
• 제30권8호
• /
• pp.790-796
• /
• 2013

Micro-speaker diaphragms play an important role in generating a desired audio response. The diaphragm is generally a circular membrane, and the cross section is a double dome, with an inner dome and an outer dome. To improve the sound quality of the speaker, a number of corrugations may be included in the outer dome region. In this study, the role of these corrugations is investigated using two kinds of finite element method (FEM) calculations. Structural FEM modeling was carried out to investigate the change in stiffness of the diaphragm when the corrugations were included. Modal FEM modeling was then carried out to compare the natural frequencies and the resulting vibrational modes of the plain and corrugated diaphragms. The effects of the corrugations on the vibration characteristics of the diaphragm are discussed.

• 한국소음진동공학회논문집
• /
• 제23권3호
• /
• pp.226-233
• /
• 2013

Individual differences in head-related transfer functions(HRTFs) were calculated using boundary element(BE) models for three Korean adults. The BE models for the individuals were developed from the computerized tomography(CT) images of the individuals. The BE models were composed of the head, pinna, and ear canal. The frequency-dependent impedance boundary conditions were imposed on the skin, hair, and tympanic membrane. The HRTFs calculated from the individual BE models showed large difference above 2 kHz in magnitude and in the locations of peaks and valleys of the frequency spectrums, which should be considered in virtual auditory sound field. The identified individual differences in the HRTFs demonstrate that the developed BE models can be utilized successfully in order to obtain the HRTFs information of individuals.

• 센서학회지
• /
• 제19권3호
• /
• pp.209-213
• /
• 2010

This paper describes the fabrication and characteristics of AlN piezoelectric MPG(micro power generator). The micro energy harvester was fabricated to convert ambient vibration energy to electrical power as a AlN piezoelectric cantilever with Si proof-mass. To be compatible with CMOS process, AlN thin film was grown at low temperature by RF magnetron sputtering and micro power generators were fabricated by MEMS technologies. X-ray diffraction pattern proved that the grown AlN film had highly(002) orientation with low value of FWHM(full width at the half maximum, $\theta=0.276^{\circ}$) in the rocking curve around(002) reflections. The implemented harvester showed the $198.5\;{\mu}m$ highest membrane displacement and generated 6.4 nW of electrical power to $80\;k{\Omega}$ resistive load with $22.6\;mV_{rms}$ voltage from 1.0 G acceleration at its resonant frequency of 389 Hz. From these results, the AlN piezoelectric MPG will be possible to suitable with the batch process and confirm the possibility for power supply in portable, mobile and wearable microsystems.

• 한국전자통신학회논문지
• /
• 제16권1호
• /
• pp.203-210
• /
• 2021

만성 전립선 염 치료의 어려움은 치료 의사뿐만 아니라 환자에게도 육체적 고통과 정신적 문제를 유발한다. 본 연구의 장치는 외부 충격파의 열적 및 기계적 상호 작용으로 인한 충격파 에너지의 진동 효과로 인해 전립선 증상으로 고통받는 환자를 돕기 위해 연구되었다. MCU와 나선형코일을 활용하여 집중된 에너지의 열 및 진동 효과를 발생시키고 이 파동을 효과적으로 적용하는 체외 충격파 치료 장치를 고안하여 전립선 염 및 전립선비대증(BPH, Benign prostatic hyperplasia)에 대한 효과적인 치료 수단을 제공하는 구조를 구현하였다.