• 제목/요약/키워드: Mechanical Vibration

검색결과 4,404건 처리시간 0.174초

Droplet transient migration and dynamic force balance mechanism on vibration-controlled micro-texture surfaces

  • Xu, Jing;Liu, Guodong;Lian, Jiadi;Ni, Jing;Xiao, Jing
    • Current Applied Physics
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    • 제18권11호
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    • pp.1368-1374
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    • 2018
  • In this paper, forced vibration was used to regulate the droplet migration, fully recording the transient migration of droplets on a micro-textured substrate under the resonance frequency by a high-speed camera. The influence of resonance frequency and dynamic migration characteristics of droplets on the solid micro-texture surface under lateral vibration were researched. The experiment demonstrates that the driving force is caused by the difference between the left and right contact angles made the droplet oscillate and migrate, and as time t increases, the left and right contact points are periodically shifted and the amplitude of migration increases. Therefore, based on the droplet migration behavior and its force balance mechanism, a spring vibration model of migration behavior of the vibrating droplet micro unit was set up to predict the complete trajectory of its migration on a solid surface. The calculation results show that the theoretical displacement is less than the experimental displacement, and the longer the time, the larger the difference. Affected by the vibration, part of the droplet permeates through the micro-texture, resulting in the droplet losing height and the contact angle becoming smaller as well. While the other part of droplet overcomes the internal surface tension to migrate.

Mechanical Characteristics of Curing Concrete Affected by Forced Vibration (가력진동이 양생중인 콘크리트에 미치는 영향에 관한 연구)

  • 이지은;권영웅
    • Proceedings of the Korea Concrete Institute Conference
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    • 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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    • pp.97-102
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    • 2000
  • The purpose of this study was performed to estimate the mechanical characteristics of curing concrete affected by forced vibration. The major variables of this test were vibration method, vibration velocity and duration of vibration, The compressive strength, slip, bending strength and displacement are measured for all the cylinder paper molds and beams. The results can be summarized as follows ; 1)According to vibration, velocity(RMS), the compressive strength, bending and displacement for continual vibration increased, but for immediate vibration decreased. 2) Immediate vibration effected on concrete compressive strength, slip than continual vibration. especially in vibration velocity 3.59mm/sec(RMS; 0.624mm/sec) slip secreased 15% in continual vibration, 20% in immediate vibration.

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A Study on the Characteristic of Noise and Vibration in 3-Phase Induction Motor for the Forklift (전동 지게차용 3 상 유도 모터의 소음 진동 특성에 대한 연구)

  • Kim, Woo-Hyung;Chung, Jin-Tai
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 한국소음진동공학회 2007년도 추계학술대회논문집
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    • pp.764-769
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    • 2007
  • This paper is studied the noise and vibration characteristics analysis of the three-phase induction AC motor of the electrical forklift. And we suggest the method which the reduction orders the noise and vibration to be the mechanical. In other to investigate these characteristics, we considered the mechanical characteristics, the electromagnetic effects, and these interactions. In mechanical, we studied the characteristic of the stator, the bearing supported condition of the rotor, and the sound radiation. In electronically, this paper is considered the harmonic effect which is related the magnetic motive force (mmf) with respect to the characteristic of the slot number of the rotor and the stator and the pole number of the motor. Finally we investigated the overall noise and vibration of the induction motor by relations between the electronically harmonic and the mechanical resonance of the stator. By the analysis of the generally three-phase induction motor, we suggest the design methodology to low noise and vibration.

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The Fire Hazard of Screwed Electric Contacts Due to Mechanical Vibration at Low Voltage Equipment

  • Choi, Chung-Seog;Kim, Young-Seok;Kim, Hyang-Kon
    • International Journal of Safety
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    • 제4권2호
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    • pp.18-23
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    • 2005
  • There are many electrical connections in the electric apparatus and most fires due to a fault contact result from a failure or misuse of electric apparatus and installation. The fault contact happens between electrical connections by the loose and the mechanical vibration. In this paper, we have investigated thermal and electrical properties of screwed electric contacts due to the mechanical vibration. The exciter was connected to a signal generator and power amplifier that provided the vibration frequency and amplitude. The vibration, temperature and voltage data were sent to a data acquisition system (DAQ). In the case that fault contact took place, the arc happened between the screwed electric contact and electric wire, heat due to the arc was transmitted to the adjacent insulators, for which the oxide could be generated more. In addition, a spark was generated and the insulator began to melt. Thus, the possibility of electrical fire became the highest in this case. Finally, when the fault contact takes place due to vibration, the hazard of an electric accident is very high.

Study of the Vibration and Shock Isolation for HEV Battery Pack (특수임무 차량 배터리 팩 진동/충격 저감 설계에 대한 연구)

  • Kim, Man-Dal;Jang, Duk-Jin;Lee, Sung-Jun;Hong, Seong-Wook
    • Journal of the Korean Society for Precision Engineering
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    • 제33권10호
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    • pp.813-820
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    • 2016
  • Hybrid Electric Vehicles (HEVs) are developed to be operated with two kinds of power source (Diesel Engine and Electric Motor with Rechargeable High Voltage Battery Pack). HEVs for military vehicle require high reliability to provide stable powers under serious environment such as vibration and shock. To ensure normal operation of battery pack under serious environment such as vibration and shock, the high voltage battery pack needs to have appropriate dynamic characteristics. This paper presents a design procedure for high voltage battery pack with such characteristics. An isolator design is proposed to reduce vibration and shock. Associated random vibration and shock response of the high voltage battery pack are simulated under conditions suggested by MIL specifications. Its dynamic characteristics and vibration and shock responses are validated with experiments.

Vibration Suppression Control for a Geared Mechanical System;Simulation Study on Vibration Suppression Effects Using a Model-Based Control with a Rotational Speed Sensor

  • Itoh, Masahiko
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 2005년도 ICCAS
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    • pp.694-699
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    • 2005
  • This paper deals with a control technique of eliminating the transient vibration of a geared mechanical system. This technique is based on a model-based control with a rotational speed sensor in order to establish the damping effect at the driven machine part. A rotational speed sensor is installed in a driven gear, namely a bull gear. A control model is composed of a reduced-order mechanical part expressed as a transfer function between the rotational speed of the motor and that of the bull gear. This control model estimates a load speed after the rotational speed of the bull gear is acted on the transfer function. The difference between the estimated load speed and the motor speed is calculated dynamically and it is added to the velocity command to suppress the transient vibration generated at the load. This control technique is applied to a dies driving spindle of a form rolling machine. In this paper, the performance of this control method is examined by simulations. The settling time of the residual vibration generated at the loading inertia can be shortened down to about 1/2 of the uncompensated vibration level.

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Signal Acquisition for Effective Prediction of Chatter Vibration in Milling Processes (밀링가공에서 효과적인 채터진동 판별을 위한 신호 획득)

  • Jo, M.H.;Kim, H.;Koo, J.Y.;Lee, J.H.;Kim, Jeong Suk
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • 제23권4호
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    • pp.325-329
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    • 2014
  • This paper proposes a method to predict chatter vibration generated in milling processes and to enhance machining quality and surface finish. Chatter vibration is a common problem in the milling of thin walls and floors. It causes a poor surface finish, or even marks, to appear on the final machined surface. Therefore, an effective method is necessary to predict chatter vibration in machine tools. In this investigation, chatter vibration is measured by an accelerometer, microphone, and Acoustic Emission (AE) sensor in a machining operation. Based on the results of the experiment, a microphone can be applied for the prediction of chatter vibration in milling processes.

A Study on Reducing Vibration of Washing Machine Using Gyroscope System (자이로스코프 시스템을 이용한 드럼 세탁기의 진동 저감 연구)

  • Na, Gyusung;Park, Youngjin;Park, Youn-Sik
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • 제24권2호
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    • pp.117-122
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    • 2014
  • A novel method to reduce the vibration of drum type washing machine is proposed. Recently, as the capacity of the drum-type washing machine gets expanded and its washing performance is improved, its market share is increasing in the whole world. But, the capacity of washing machine is limited because of door size and built-in washing machine size. The vibration of washing machine is caused by unbalanced cloths in high spining drum, and the displacement of tub is maximized at transient range about 3 Hz(180 rpm). Previous researches were concerned about steady-state vibration in spinning. In this study, concerned about transient vibration and the displacement of tub is decreased by using gyroscope system. Mutibody dynamic model of washing machine include gyroscope is designed and the vibration of tub have been reduced by 44.7 % over original.

EFFECT OF IN-SITU VIBRATION ON THE PROPERTIES OF A-GRADE STEEL SMA WELDMENT

  • Park, Tae-Dong;Kim, Ha-Geun;Youn, Joong-Geun
    • Proceedings of the KWS Conference
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    • 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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    • pp.408-411
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    • 2002
  • Effect of in-situ vibration on the properties of A-grade steel SMA weldment has been investigated. Welding was performed on the steel fixed at the experimental jig under the mechanical vibration of a given frequency. The applied frequency varied from 39 to 43.5 Hz (harmonic frequency). For weldments formed under the vibration with a sub-harmonic frequency, both the columnar width of the weld metal and the prior austenite grain size of the HAZ near the fusion line clearly decreased. This indicates that the vibration increase the cooling rate after welding. Vibration effect was also found at the weld metal formed at the center region of the weldment. The weld metal showed liner microstructure both in columnar zone and in equiaxed zone with thinner grain boundary ferrite. However mechanical properties of the weld metal did not exactly follow the microstructural changes developed under the vibration. The weld metal formed under the vibration revealed higher yield and tensile strength but lower ductility and impact toughness, compared with the conventional weld metal.

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Diagnostics and Prognostics Based on Adaptive Time-Frequency Feature Discrimination

  • Oh, Jae-Hyuk;Kim, Chang-Gu;Cho, Young-Man
    • Journal of Mechanical Science and Technology
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    • 제18권9호
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    • pp.1537-1548
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    • 2004
  • This paper presents a novel diagnostic technique for monitoring the system conditions and detecting failure modes and precursors based on wavelet-packet analysis of external noise/vibration measurements. The capability is based on extracting relevant features of noise/vibration data that best discriminate systems with different noise/vibration signatures by analyzing external measurements of noise/vibration in the time-frequency domain. By virtue of their localized nature both in time and frequency, the identified features help to reveal faults at the level of components in a mechanical system in addition to the existence of certain faults. A prima-facie case is made via application of the proposed approach to fault detection in scroll and rotary compressors, although the methods and algorithms are very general in nature. The proposed technique has successfully identified the existence of specific faults in the scroll and rotary compressors. In addition, its capability of tracking the severity of specific faults in the rotary compressors indicates that the technique has a potential to be used as a prognostic tool.