• Title/Summary/Keyword: Loss Factor

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Lateral Vibration of Beams with a Bonded Lap Joint and Partial Layered Dampers (겹침이음부 및 국부적 층댐퍼를 갖는 보의 횡진동 특성)

  • 박정일;최낙삼
    • Journal of KSNVE
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    • v.9 no.1
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    • pp.174-183
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    • 1999
  • An analytical model for the lateral vibration of beams with a bonded lap joint and partial layered dampers has been proposed in this paper. Both shear and normal forces acting along the interface between the elastic and viscoelastic layers were considered in the vibration analysis. Analytical results were compared with those obtained by a finite element method. Effects of the size and location of layers in partial dampers on system loss factor($\eta_s$) and resonant frequency($\omega_r$) were studied. which showed that partial dampers adhered to the site exhibiting the maximum amplitude of vibration were most influential in the increase of $\eta_s$ and the decrease of $\omega_r$. Specific system loss factor( $\eta_s$ divided by total mass of system) was also evaluated in the analysis.

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Study on Resonant PWM Switching Technique for $3{\phi}$ Boost AC/DC Converter with High Power Factor and Less Switching Loss (3상 승압형 AC/DC 컨버터의 고역율과 스위칭 손실 저감을 위한 공진 PWM 스위칭 기법에 관한 연구)

  • Yi, Eun-Gyu;Noh, Yung-Nam;Kim, Beung-Jin;Jeon, Hee-Jong
    • Proceedings of the KIEE Conference
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    • 1997.11a
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    • pp.541-543
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    • 1997
  • In this paper, a proposed resonant PWM switching technique makes the boost AC/DC converter to high input power factor and less switching loss. Also, the switching control scheme is used which minimize harmonic components employing novel PWM technique. In addition, an employment of resonant circuit for switching makes zero current switching(ZCS) and zero voltage switching(ZVS) for control switches without switching losses. The result shows that high power factor is still for varying load and switching loss is very low.

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Test method comparison for vibration-damping of materials (물질의 진동감쇠 시험법 비교)

  • 신수현;이용봉;정성수;조승일
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.11a
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    • pp.700-703
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    • 2003
  • The test method of ASTM E 756 and KS D 0076 to estimate vibration-damping properties is compared. Comparison method depending on specimen support, exciting method and calculation method for loss factor is used. Half-power bandwidth method and vibration decay method is used in the calculation method for loss factor, and Young's modulus is decided by geometric character and density for specimen and resonance frequency. Vibration measurement sensor is compared by using non-contact displacement detector, velocity detector and accelerometer. This paper is also presented the matter which is able to cause error in the measurement

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A Study on the Optimum Design of Constrained layer for the Damping of Flexural Vibration (굽힘진동 감쇠를 위한 구속층의 최적설계에 관한 연구)

  • 김사수;이민우
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1997.04a
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    • pp.95-101
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    • 1997
  • A general method is presented for the analysis of the damping effectiveness of viscoelastic layer applied to elastic beam. The damping is attributed to the shear deformations of the treatment. Specific results are then given for sandwich beams with dissipative cores. The calculated results by this method are validated by comparison with the experimental results. Optimum design of a viscoelastic damping layer which is constrainedly cohered on a steel beam is discussed from the viewpoint of the modal loss factor. An object function is a loss factor of 3-layered beam and design variable is the thickness of constraining layer and viscoelastic layer. Optimum thickness can be obtained when 3-layered beam has a maximum loss factor.

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A Study on the Evaluation of the Loss Factor and Young′s Modulus of Damping Materials on Temperature Condition (2층형 제진 강판을 이용한 오도 조건에 따른 제진재의 손실계수 및 탄성계수 측정)

  • Lee, Chang-Myung;Lee, Jun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.11 no.9
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    • pp.391-397
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    • 2001
  • The characteristic values of damping materials are variant on frequency and temperature. We measure the characteristic values(loss factor, young\\\\`s modulus) of damping materials in vibration test. We can not measure characteristic values of damping materials by themselves. So, we proposed a method, sticking damping material to thin steel beam and measuring of characteristic values of damping material on frequency and temperature. We didn\\\\`t use constraining layer but we measured characteristic values on conditioning temperature.

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Dielectric Properties of Fresh Ginseng Determined by an Open-Ended Coaxial Probe Technique (수삼의 마이크로파 유전특성)

  • Hong, Seok-In;Lee, Boo-Yong;Park, Dong-June;Oh, Seung-Yong
    • Korean Journal of Food Science and Technology
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    • v.28 no.3
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    • pp.470-474
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    • 1996
  • The dielectric properties, dielectric constant (${\varepsilon}‘$) and loss factor (${\varepsilon}’$), of skin and pulp of fresh ginseng were measured from $25^{\circ}C$ to $67^{\circ}C$ using an open-ended coaxial probe technique for 915 MHz and 2450 MHz. Pulp and skin had dielectric constant of $30{\sim}64$ and loss factor between 10 and 20, each variable having a respective frequency dependence typical of materials with high water content. Although the loss factor was nearly constant, the dielectric constant increased as moisture content increased. The dielectric constant of ginseng pulp increased as temperature increased (temperature ${\leq}56^{\circ}C$), but any significant differences were not found in skin dielectric properties. Penetration depth for fresh ginseng were about 2 cm at 91.5 MHz and 1cm at 2450 MHz.

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Sound Radiation due to Tire Tread Vibration (타이어 트레드의 진동에 의한 음향방사)

  • Kim, Byoung-Sam;Hong, Dong-Pyo;Chung, Tae-Jin
    • The Journal of the Acoustical Society of Korea
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    • v.13 no.2
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    • pp.13-22
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    • 1994
  • A theoretical model is studied to describe the sound radiation by the surface vibration of in-service tires. The tire is modeled as a circular ring model. The effects of normalized frequency and structrual loss factor are included. Through numerical integration of the sound pressure, the radiated sound power is calculated as a fuction of normalized frequency and structural loss factor. The basic sound radiation mechanism is shown to be the damped progressive wave field on the structure in the vicinity of the applied force. The results indicate that the potential sound reduction might be obtained if values of normalized frequency and structural loss factor are investigated.

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Estimation of Vibration-damping Properties for Steel Beam (Steel beam의 진동감쇠 특성평가)

  • Shin, Su-Hyun;Nam, Hyo-Duk;Jung, Sung-Soo;Lee, Young-Bong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.11a
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    • pp.439-442
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    • 2003
  • The test method of ASTM E 756 and JIS G 0602 to estimate vibration-damping properties is presented. Measurement method depending on specimen support, exciting method and calculation method for loss factor is used. Half-power bandwidth method and vibration decay method is used in the calculation method for loss factor, and Young's modulus is decided by geometric character and density for specimen and resonance frequency. Vibration measurement sensor is compared by using non-contact displacement detector, velocity detector and accelerometer. The cause of measurement error is also presented.

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A study of the method of computing Transmission cost in competitive market (경쟁적 전력시장에서 적용 가능한 송전선이용료 산정기법에 관한 연구)

  • Kim, Kyung-Min;Kim, Kang-Wan;Kim, Jong-Man;Han, Seok-Man;Kim, Bal-Ho H.
    • Proceedings of the KIEE Conference
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    • 2004.11b
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    • pp.284-286
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    • 2004
  • When Power market is restructured, we have an argument with selecting Transmission loss factors. First, we determine the method of calculating Transmission loss factor using OPF (Optimal Power Flow) or PF (Power Flow Equation). Then, we decide that we applicate the factor which are identical value all the year or which are floating Transmission loss factor every each hour. In this study, we accomplish the method of computing Transmission cost in competitive market.

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A Study on the Dynamic Properties by Loading Time of Floor Impact Noise Insulation Materials (바닥충격음 완충재의 재하시간에 따른 동적 특성 연구)

  • Kim, Heung-Sik;Jin, Pil-Hwa;Joo, Si-Woong;Jung, Sung-Won
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11a
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    • pp.942-945
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    • 2005
  • The purpose of this study is to suggest a fundamental data for change of dynamic properties according to the loading time of resilient materials. 18 kinds of resilient materials included 4 representative types were measured at the load time of 24hours and 2hours by the method of Korea standard (KS F 2868) measuring the dynamic stiffness and the loss factor of materials under floating floors. As a result, the dynamic stiffness was increased rapidly in case of expandable polystyrene and rubber materials according to the load time, especially before 2 hours. The loss factor was represented that rubber materials with high elasticity are high, and expandable polystyrene, polyester, poly ethylene materials with low elasticity are low.

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