• Title/Summary/Keyword: Hammering test

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A Basic Experimental Study on the Squeak Noise Using the Pin-on-disk (Pin-on-disk를 이용한 기초 마찰소음 실험 연구)

  • Nam, Jae-Hyun;Kang, Jae-Young
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.8
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    • pp.736-741
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    • 2012
  • Squeak noise is studied by using the pin-on-disk system with aluminum pin and steel disk. Noise induced by friction is measured with respect to the normal loads and sliding speeds. The negative slope of friction-velocity curve is seen when the squeak noise occurs. It is found that the normal load influences on the sound level of squeak noise. From the hammering test, the major frequency of the squeak noise is shown to correspond to one of system modes, which implies that squeak phenomenon arises from the unstable system modes. The result of FE analysis shows that the major squeak mode is the bending mode of the pin.

Analysis of Noise Source for Mold Transformer (몰드변압기의 소음 원인 분석)

  • Choi, W.H.;Kim, W.C.
    • Journal of Power System Engineering
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    • v.4 no.4
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    • pp.59-64
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    • 2000
  • Especially, demands for the noise reduction of mold transformer has been becoming an common issue because it has been used mainly at the residence area such as building and ship. So, this paper investigates the noise source and countermeasure of mold transformer radiated high noise abnormally. The result of impact hammering test for core of transformer ascertains the core resonance by harmonics of line frequency and high noise can be reduced to avoid core resonance by changing torque strength of tie rod. Magnetic field analysis is performed to identify the reason that noise of V-phase is higher than U and W-phase in the normal condition. It is the cause that flux density and magnetic force of V-phase is higher than the other phase respectively.

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Analysis of the change in appearance according to the hardening method of leather (가죽의 경화방법에 따른 외형변화 분석)

  • Youshin, Park
    • Journal of Fashion Business
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    • v.26 no.5
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    • pp.122-134
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    • 2022
  • This study is conducted on hardening leather with improved firmness and stability of shape, based on research on types and thickness of leather. The purpose of this study is to test the physical properties of the leather for molding to prepare the foundation for leather molding based on the test results using four methods by thickness of Vegetable and Split. The tests were conducted using a total of five leather types, including three types of vegetable leathers and two types of split, by thickness. Based on the testing method for leathers in KS M 6882, the tests were performed at 27℃ with relative humidity of 65±20%. The samples were prepared with cowhide, size 9cm× 2cm. The measurement parameters are length and width. thickness, volume, mass, density. Regarding the hardening treatment method, changes in appearance and major physical characteristics of leather were reviewed by soaking in hot water, dry heating, hammering, waxing, and olive oil coating. The study results are as follows. In planar works, it is judged that hardening work using a hammer is more suitable for stiffness or density in order to prevent easy breakage with adult muscle density, rather than boiling water or baking. In conclusion, there is no curling, soot, or breaking phenomenon, and the densest curing method is 50℃ for 20 sec of V2 and 75℃ for 60 sec of V2 in boiling water. The combination of paraffin treatment improve waterproof and quality.

Earthquake Analysis of Dam Floodgate Using Calibrated Added Mass (보정된 부가질량을 이용한 댐 수문의 지진해석)

  • Bea, Jung-Ju;Kim, Ho-Seung;Kim, Yong-Gon;Lee, Jee-Ho
    • Journal of the Earthquake Engineering Society of Korea
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    • v.13 no.5
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    • pp.31-40
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    • 2009
  • In this paper, a trial-error based method is presented to calibrate added mass models through numerical iterations minimizing the difference between the measured frequency data and its numerical simulation result for a dam floodgate. Earthquake analysis of the real floodgate for which the on-site hammering vibration test is performed show that the classical Westergaard added mass model gives relatively larger values in the maximum earthquake force and the maximum total displacement than the present added mass model, based on the calibration of on-site measurement data.

Seismic Noise Reduction Using Micro-Site Array Stacking (미소-위치 배열 중합을 이용한 지진파의 잡음제거)

  • Choi, Hun;Sohn, Sang-Wook;Bae, Hyeon-Deok
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.63 no.3
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    • pp.395-403
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    • 2014
  • This paper presents a new approach to improve the signal to noise ratio (SNR) for local seismic disaster preventing system in densely populated area. The seismic data measured in the local site includes various sensing noises (offset or measurement noise) and man-made/natural noises (road and rail traffic noise, rotating or hammering machinery noise, human activity noise such as walking and running, wind/atmospheric pressure-generated noise, etc.). These additive noises are different in time and frequency characters. The proposed method uses 3-stages processing to reduce these different additive noises. In the first stage, misalignment offset noise are diminished by time average processing, and then the second and third stages, coherent/incoherent noises such as man-made/natural noises are suppressed by array stacking. In addition, we derived the theoretical equation of the SNR gain improved by the proposed method. To evaluate the performance of the proposed method, computer simulations were performed with real seismic data and test equipment generated data as the input.

A Study on the Propeller Blade Singing Place of an 86,000 Ton Deadweight Crude Oil Tanker (86,000톤 원유운반선 프로펠러 날개의 singing(명음) 발생위치 조사)

  • Dong-Hae Kim;Kyoon-Yang Chung
    • Journal of the Society of Naval Architects of Korea
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    • v.31 no.3
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    • pp.59-64
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    • 1994
  • A study was conducted to investigate the propeller singing place of an 86, 000 ton Deadweight Crude Oil Tanker. In preliminary study, proper use of finite element analysis was verified by comparing with the result of hammering test in the air. Then the finite element analysis was carried out for the blade in the water and compared with the noise measurement during sea trial, which enabled to confirm the local resonances of blade structure. Result of the study showed that the singing occurred most probably at trailing edges on the blade tip over 95% of propeller diameter. Owing to edge cutting of a successfoul remdial action, the singing excitation forces seemed to be reduced whereas the vibration characteristics of the blade was not changed.

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Torsional Damping Estimation of a Segmented Hull Model with Modal Coupling (모드 연성을 수반하는 분할 모형의 비틀림 감쇠비 추정)

  • Kim, Yooil;Park, Sung-Gun
    • Journal of the Society of Naval Architects of Korea
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    • v.53 no.6
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    • pp.482-493
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    • 2016
  • The identification of modal damping of a segmented hull model with torsional response is difficult task due to the coupling of modal response. This is because the 1st and 2nd torsional vibration modes are closely spaced in frequency domain leading to the situation that the modal decomposition is difficult to achieve by simple band-pass filter. Present study applied several different modal decomposition methods to derive the damping ratio of different modes. The modal decomposition methods considered in this study are simple band-pass filter, Hilbert vibration decomposition, Wavelet transform and proper orthogonal decomposition. Coupled free decay signal obtained from the torsional hammering test on a segmented hull model was processed with four different methods and the derived damping ratios were compared with each other. Discussions also have been made on the pros and cons of the different methodologies.

CPVC Valve Tightening Torque Impact Sockets on the Leaks (CPVC 밸브소켓 체결토크가 누수발생에 미치는 영향)

  • Lim, Chun-Ki;Baek, Eun-Sun
    • Fire Science and Engineering
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    • v.30 no.4
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    • pp.46-58
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    • 2016
  • In this study, the stress applied to screw section, strain, displacement, von Mises stress, and the compression stress applied to the rubber packing for watertightness are estimated with computer simulation when the tightening torque of valve socket is in the range of $10{\sim}130N{\cdot}m$ in order to analyze the influence of valve socket screw section in accordance with the excessive tightening which is supposed to be the cause of water leakage from the synthetic resin piping for fire fighting application of sprinkler equipment, and for the sake of verifying this, adequate value of tightening torque and the value of the compression stress of rubber packing are investigated by examining the number of connected thread for each tightening torque, the deformation state of valve socket and rubber packing and conducting the water hammering test. The result of this test is expected to be utilized as the data required for revising the standard or technical criteria to prevent the water leakage of the synthetic resin piping for fire fighting application.

Fabrication of semiconductor optical switch module using laser welding technique (반도체 광스위치 모듈의 제작 및 특성연구)

  • 강승구
    • Korean Journal of Optics and Photonics
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    • v.10 no.1
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    • pp.73-79
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    • 1999
  • Semiconductor optical switch modules of 1$\times$2, 1$\times$4, and 4$\times$4 types for 1550 nm optical communication systems were fabricated by using laser welding technique, embodying in 30-pin butterfly package. For better coupling efficiency between switch chip and optical fiber, tapered fibers of 10~15mm lens radii were used, which provided up to 60% optical coupling efficiency. With the help of new laser hammering process, we could recover the lost optical power almost completely up to average 82% of initially obtained power. The fabricated optical switch modules showed good thermal stability of less than 5% degradation even after 200 times thermal cycling test. The 2.5 Gbps optical transmission characteristics of the 4$\times$4 switch module showed low sensitivities of less than -30dB for all possible switching paths. The transmission penalties of 1$\times$2 switch module at $10^{-10}$ BER were 0.6dB and 0.7dB for 50Xm and 90 Km optical fibers, respectively.

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Characteristic of Friction on Texturing Bearing Steel with Ultrasonic Hole Machine

  • Shin, Mijung;H., Angga Senoaji;Kwon, SoonHong;Chung, SungWon;Kwon, SoonGoo;Park, JongMin;Kim, JongSoon;Choi, WonSik
    • Tribology and Lubricants
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    • v.31 no.1
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    • pp.21-27
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    • 2015
  • We carry out experiments to characterize textured bearing steel with varying hole density and depth. Textured surface is believed to reduce the friction coefficient, and improve performance and wearing caused by third-body contact. We employ three lubrication regime conditions based on the Stribeck curve: boundary lubrication, mixed lubrication, and hydrodynamic lubrication. Ultrasonic machining is an untraditional machining method wherein abrasive grit particles are used. The hammering process on the work piece surface by abrasive provides the desired form. In this study, we create multi-holes on the bearing steel surface for texturing purposes. Holes are formed by an ultrasonic machine with a diameter of 0.534 mm and a depth of about 2-4 mm, and they are distributed on the contact surface with a density between 1.37-2.23%. The hole density over the surface area is an important factor affecting the friction. We test nine types of textured specimens using four times replication and compare them with the untextured specimen using graphs, as well as photographs taken using a scanning electron microscope. We use Analyzes variant in this experiment to find the correlation between each pair of treatments. Finally, we report the effect of hole density and depth on the friction coefficient.