• Title/Summary/Keyword: Peak vibration value

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Measurement of Loss Factor and Young's Modulus of ABS and PP Specimens by Using a Speaker (스피커를 이용한 ABS와 PP의 손실계수 및 영률 측정)

  • Jeon, Byeong Su;Jung, Sung Soo;Lee, Jong Kyu
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.9
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    • pp.724-730
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    • 2014
  • It is essential to control noise and vibration in various industrial fields. In the automobile industry, various plastics have been developed and replaced metallic materials in order to reduce mass and vibration effectively. In this study, we measured and analyzed the Young's moduli and the loss factors of Acrylonitrile butadiene styrene(ABS) and Polypropylene(PP). In order to solve the fundamental error to determine the two quantities, a loudspeaker was used instead of conventional electromagnetic devices to generate bending motion to the specimens and a laser vibrometer was also used in detection of vibration signal of the specimen. The measured Young's moduli and loss factors of the ABS specimen were nearly constant as the temperature($-10{\sim}60^{\circ}C$) was increased. The loss factor of PP specimen showed peak value at $20^{\circ}C$ and it means that there is glass transition for the PP specimen. Young's modulus of PP specimen was linearly decreased as the temperature was increased.

Seismic response control of irregular asymmetric structure with voided slabs by distributed tuned rotary mass damper devices

  • Shujin Li;Irakoze Jean Paula;Ling Mao
    • Earthquakes and Structures
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    • v.25 no.6
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    • pp.455-467
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    • 2023
  • This study focuses on demonstrating the effectiveness of vibration control of tuned rotary mass damper (TRMD) for reducing the bidirectional and torsional response of the irregular asymmetric structure with voided slabs under earthquake excitations. The TRMD arranged in plane of one-story eccentric structure is proposed as a distributed tuned rotary mass damper (DTRMD) system. Lagrange's equation is used to derive the equations of motion of the controlled system. The optimum position and number of TRMD are numerically investigated under harmonic excitation and the control effects of different distributions are discussed. Furthermore, a shaking table test is conducted under different excitation cases, including free vibration, forced vibration and seismic wave to investigate the absorption performance of the device. The numerical simulations of different distributions of the TRMDs show that the DTRMDs are more effective in reduction of the displacement response of the asymmetric structure under the same mass ratio, even when the degree of eccentricity becomes large. However, with small degree of eccentricity, the unreasonable asymmetrical arrangement may cause the increase of the peak value of the rotational angular displacement. Finally, the experimental investigations exhibit similar results of translational displacement of the structure. It is concluded that the vibration of the irregular asymmetric structure can be controlled more economically and effectively by reducing the mass ratio through reducing the quantity of TRMDs at the high stiffness end.

Prediction of Non-cavitation Noise from Large Scale Marine Propeller (수치해석을 통한 대형 선박용 프로펠러의 비공동소음 예측)

  • Ryu, Ki-Wahn;Lee, Jong-Yeol;Kim, Bong-Ki;Byun, Jeong-Woo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.25 no.2
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    • pp.75-82
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    • 2015
  • Noises from the large scale marine propeller are calculated numerically on non-cavitation condition. The hydrodynamic analysis is carried out by potential based panel method with time marching free wake approach. The distribution of hydrodynamic loads on the propeller surface and noise signals are obtained using the unsteady Bernoulli's equation and the Farasssat's formula respectively. It turns out that the noise signal at the narrow band shows strong peak at the blade passage frequency, and the peak value at the 1/3 octave band also shows the same trend. Noise signals and directivity patterns for both the thickness and the loading noise are compared with each other. The directivity pattern for the loading noise shows minor lobe at the backward side of the rotating disc plane.

Comparison of Vibration Characteristics of Cargo Bikes on General Roads and Bicycle Roads (일반도로와 자전거도로에서의 카고바이크 화물 적재함 진동 특성 비교)

  • Dong Yul Kim;Myenog Guk Yu;Heng Suk Lee;Sang Min Kim
    • KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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    • v.29 no.3
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    • pp.175-179
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    • 2023
  • This paper analyzes the vibration characteristics within the cargo compartment of a three-wheeled cargo bike when used on both regular roads and dedicated bicycle lanes. When cargo is loaded into the cargo compartment of a cargo bike and driven on the road, the shocks and vibrations transmitted from the ground can potentially affect the transported goods and even lead to product damage. As the vibration characteristics applied to the cargo compartment may vary depending on the condition of the road, vibration sensors were attached to the cargo bike's cargo compartment for data collection during operation on different road types. According to KS T ISO 13355 standards, the cargo bike can withstand vibrations within the range of 10 Hz to 60 Hz when operating on both bicycle lanes and regular roads. However, it is observed that there are peaks exceeding the profile in the frequency range of 3-6 Hz. In the 70-200 Hz range, the profile is exceeded on both regular roads and bicycle lanes, with a tendency for higher exceedance on bicycle lanes. The Grms value within the frequency range of KS T ISO 13355 is 5.926 m/s2 (0.604 Grms). When operating on bicycle lanes with cargo, the Peak envelope optimization PSD value is 6.553 Grms, while on bicycle lanes, it is 7.708 Grms, indicating a difference of at least tenfold.

Ultra-precision Cutting of Polycarbonate for Optical Components by Using Elliptical Vibration Cutting Method (타원진동절삭가공법에 의한 광학부품용 폴리카보네이트 수지의 초정밀가공)

  • Song, Young-Chan;Park, Chun-Hong
    • Journal of the Korean Society for Precision Engineering
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    • v.26 no.6
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    • pp.42-49
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    • 2009
  • The optical elements made of plastics are normally produced by mass production such as injection molding with use of precision dies and molds. It costs to prepare the dies and molds, and it is only justified to prepare such expensive dies and molds when the parts are massively produced. On the other hand, it is too expensive and inefficient when precision plastic parts are needed only in small quantities, such as a case of trial manufacturing of new products. An ultra-precision diamond cutting is one of promising processes to produce the precision plastic parts in such cases. But it is commonly believed that an ultra-precision cutting of plastics for optical components is very difficult, because they are thermo-plastic material. In the present research, an ultra-precision diamond cutting of polycarbonate (PC), that is one of typical optical materials, was tried by using elliptical vibration cutting method. It is experimentally proved that good optical surfaces were obtained by using elliptical vibration cutting in cases of grooving and flat surfaces. The maximum surface roughness of less than 60 nm in peak to valley value is acquired.

Study on Vibration Characteristics in terms of Airfoil Cross-Sectional Shape by Using Co-rotational Plane Beam-Transient analysis (Co-rotational Plane beam-Transient analysis를 이용한 에어포일 단면 형상 변화에 따른 진동특성 연구)

  • Kim, Se-Ill;Kim, Yong-Se;Park, Chul-Woo;Shin, SangJoon
    • Proceeding of EDISON Challenge
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    • 2016.03a
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    • pp.203-208
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    • 2016
  • In this paper, vibration characteristics in terms of the airfoil cross-sectional shape was examined by using the EDISON co-rotational plane beam-transient analysis. Assuming aircraft wing as a cantilevered beam with a constant cross-sectional shape, natural frequencies of each airfoil shape was compared while varying airfoil maximum thickness and maximum camber length, using Fast Fourier Transformation(FFT). When the airfoil maximum thickness was varied, natural frequency showed peak value at 18% chord, and decreased afterwards. When the airfoil maximum camber length was varied, natural frequency either increased or decreased at 6% chord, while at 8% the natural frequency showed its maximum. Applying such trends to B-737 wing airfoil, an improved B-737_mod airfoil shape was obtained with regard to the vibration characteristics.

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Frequency Characteristics of a Membrane-Cavity System and its Applications (박막-공동계의 주파수 특성과 응용)

  • 김양한;임종민
    • Journal of KSNVE
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    • v.9 no.6
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    • pp.1123-1130
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    • 1999
  • A system which is composed of a membrane and an air cavity is studied. To analyze the low frequency characteristics of a single membrane-cavity system, a plane wave model is derived. The relations among system variables, such as tension, density and stiffness, are investigated. Absorption coefficient has a maximum value at a peak frequency. In addition, a membrane-cavity system absorbs the low frequency noise with a band around peak frequency. This band is primarily determined by damping effect of the system. Furthermore, a multiple membrane-cavity system is investigated by using the transfer matrix method. To show the practical applicability of the proposed model, extensive experiments were conducted. Results show that a multiple membrane-cavity system can have broader noise reduction in the low frequency range than single.

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Portable Piezoelectric Film-based Glove Sensor System for Detecting Internal Defects of Watermelon (수박 내부결함판정을 위한 휴대형 압전형 장갑 센서시스템)

  • Choi, Dong-Soo;Lee, Young-Hee;Choi, Seung-Ryul;Kim, Hak-Jin;Park, Jong-Min;Kato, Koro
    • Journal of Biosystems Engineering
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    • v.33 no.1
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    • pp.30-37
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    • 2008
  • Dynamic excitation and response analysis is an acceptable method to determine some of physical properties of agricultural product for quality evaluation. There is a difference in the internal viscoelasticity between sound and defective fruits due to the difference of geometric structures, thereby showing different vibration characteristics. This study was carried out to develop a portable piezoelectric film-based glove sensor system that can separate internally damaged watermelons from sound ones using an acoustic impulse response technique. Two piezoelectric sensors based on polyvinylidene fluoride (PVDF) films to measure an impact force and vibration response were separately mounted on each glove. Various signal parameters including number of peaks, energy ratio, standard deviation of peak to peak distance, zero-crossing rate, and integral value of peaks were examined to develop a regression-estimated model. When using SMLR (Stepwise Multiple Linear Regression) analysis in SAS, three parameters, i.e., zeros value, number of peaks, and standard deviation of peaks were selected as usable factors with a coefficient of determination ($r^2$) of 0.92 and a standard error of calibration (SEC) of 0.15. In the validation tests using twenty watermelon samples (sound 9, defective 11), the developed model provided good capability showing a classification accuracy of 95%.

Shock Resistance Analysis of a Propulsion Motor for Naval Vessels (함정용 추진전동기의 내충격성 해석)

  • Bae, Sung-Wook;Hong, Chin-Suk;Jeong, Weui-Bong;Park, Young-Su;Bin, Jae-Goo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.12
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    • pp.1183-1189
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    • 2010
  • Shock-resistance test for a real equipment for a normal vessel is one of the difficult problem in many cases because of terrible cost and weight. An analysis technique to evaluate the shock resistance in a design stage is necessary, instead In this paper, the process to evaluate the shock resistance of a propulsion motor for naval vessels was presented based on German navy's BV043 regulation. The shock signal to impose the equipment under the test was first evaluated, and was then applied to the structural FE model of the equipment. From the transient FEA, the time history of von-Mises stress was obtained by the mode superposition method. The shock resistance was evaluated using the peak value of the von-Mises stress.

A Comparative Study on the Temporomandibular Joint Sounds before and after Occlusal Splint Therapy Using Electrovibratography (두개하악장애환자의 교합안정장치에 의한 치료후 Sonopak을 이용한 악관절음 변화)

  • Hye-Sook Park;Jong-Hoon Choi;Chang-Seo Park
    • Journal of Oral Medicine and Pain
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    • v.21 no.1
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    • pp.67-78
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    • 1996
  • This study was performed to compare the TMJ sounds by means of vibration-related items by Sonopak such as integral, high integral, above 300/(0-300) ratio, peak amplitude, peak frequency and median frequency before and after occlusa1 splint therapy as well as counselling, physical modalities. For this study 22 patients with craniomandibular disorders (CMDs) were selected and examined by routine diagnostic procedure for CMDs including Transcranial and Panoramic radiographs and were classified into 3 CMDs subgroups : disc displacement with reduction, disc displacement without reduction, and degenerative joint disease. Visual analogue scale (VAS) about joint sound was recorded during treatment period and VAS treatment index (VAS Ti) was calculated from the VAS data and treatment duration. The author evaluated and compared treatment results by several parmeters such as symptom duration, timing of joint sound, parafunctional habits, trauma, and diagnostic classification. The obtained results were as follows : 1. Before the treatment, the highest value of peak amplitude was observed in disc displacement with reduction group and value of median frequency was highest in degenerative joint disease group. In addition the highest values of peak frequency and ratio ware observed in degenerative joint disease group, though they were not significant. Furthermore the lowest value of high integral was observed in disc displacement without reduction group and though it was not significant, value of integral was lowest in that group. 2. Among 3CMDs subgroups disc displacement with reduction group showed the significantly decreased value of high integral and degenerative joint disease group had the significantly decreased value of integral after conservative treatment including occlusal splint therapy. Conclusively conservative treatment including occlusal splint therapy vay be effective in the treatment of CMDs including TMJ sound. 3. Fair prognosis for conservative treatment was observed in acute group under 6 months than chronic group, 6 months over in symptom duration but there was no statistical difference. The result for conservative treatment was observed slightly poor in subjects with bruxism, clenching, unilateral chewing habit and trauma history but there were no statistical differences.

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