• Title/Summary/Keyword: Impact hammer

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Laboratory Tests for the Applicability of Various Testing Devices for Measuring Degree of Compaction (여러가지 다짐 평가장비의 적용성을 위한 실내시험)

  • Yoo, Wan-Kyu;Lim, Nam-Gyu;Kim, Byoung-Il;Kim, Ju-Hyong
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.03a
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    • pp.1178-1187
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    • 2008
  • Quality assurance for embankment compaction is one of very important procedures to guarantee high quality construction. However, only sand replacement method (KS F2312) and static plate load test (KS F2310) which are conventional and tiresome methods are used to evaluate degree of compaction at construction fields. Recently, new types of devices such as the geogauge and the light falling weight deflectometer (LFWD), the soil impact hammer (CASPFOL) and dynamic cone penetration test etc. which are able to substitute for the conventional methods are begun to use to evaluate soil stiffness. In this study, a laboratory model test was performed to evaluate correlations among test results obtained from the new devices and to assess the potential use of them. All test results have correlations with relative density and water content. Especially, the coefficients of correlation between $E_G$ from the geogauge and $K_{30'}$ from the soil impact hammer and between $E_G$ from the geogauge and $E_{LFWD}$ from LFWD are more than 0.7 but those between the results from DCP and others are less than those between $E_{G{\cdot}}$ and $K_{30'}$ and $E_G$ and $E_{LFWD}$.

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The Grinding Characteristics of the Metal Components in Printed Circuit Boards(PCBs) Scrap by the Swing-Hammer Type Impact Mill (충격형 분쇄기 에 의한 폐프린트배선기판(PCBs) 중 금속성분의 분쇄 특성)

  • 이재천;길대섭;남철우;최철준
    • Resources Recycling
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    • v.11 no.2
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    • pp.28-35
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    • 2002
  • A study on the grinding characteristics of metal components in printed circuit boards (PCBs) scrap by a swing-hammer typeimpact mill was conducted. The PCBs scrap crushed to sizes less than 3 mm were pulverized to liberate metal components by the impact mill. The effect of rotation speed of hammer on the grinding characteristics was investigated. The particle size distribution and degree of liberation of metals such as copper and solder were measured. The effect of rotation speed and particle size on the shape sorting of metal Particles from milled PCBs was investigated using an inclined vibrating Plate. At the hammer speed of 61.3 m/s about 80% of the copper particles became larger than 297 $\mu$m while 90% of solder particles was smaller than 297 $\mu$m. In the shape sorting method, the recovery location becomes shorter as the rotation speed of hammer increases. The recovery location for particles larger than 297$\mu$m was shorter than for particles sized between 149$\mu$m and 297$\mu$m. As the recovery location becomes shorter, KI value increases towards unity while $\phi_{c}$ value decreases towards unity indicating the more roundness of metal particles.

An Experimental Study on the Free Vibration of the Steel and Composite Cylindrical Shells with Simply Supported Edge Conditions (단순지지된 Steel 및 복합재료 원통셸의 진동에 대한 실험적 고찰)

  • 이영신;최명환;길기남;송근영
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1998.04a
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    • pp.334-339
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    • 1998
  • The free vibration analysis of the simply supported steel and composite cylindrical shells are investigated. The natural frequencies and mode shapes of the shell are experimentally obtained by impact testing using an impact hammer and an accelerometer. The effects of the material and geometry on the vibrational characteristics of the shell are examined. The experimental results are compared with the analytical and a finite element results. They showed good agreement with each other.

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Free Vibration Analysis of Circular Cylindrical Shells with Longitudinal, Interior Rectangular Plate (내부에 길이방향 사각판이 부착된 원통셸의 자유진동 해석)

  • 이영신;최명환;류충현
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1997.04a
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    • pp.205-210
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    • 1997
  • The analysis of the free vibrations of a circular cylindrical shell with a logitudinal, interior rectangular plate is performed. The natural frequencies and the mode shapes of the combined shells are experimentally obtained by impact testing using an impact hammer and an accelerometer. The effects of the position of the plate on the frequencies and mode shapes of the combined system are examined. The experimental results are compared with a finite element analysis and show good agreement.

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Small-size Specimen's Effectiveness That is Used to Mortar Layer of Slab (Heavy-weight Floor Impact Sound) (슬래브 상부 몰탈층에 사용된 작은시편의 유효성 검토(중량충격음을 중심으로))

  • Chung, Jin-Yun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.2
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    • pp.184-191
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    • 2009
  • This study examined small-size specimen's effectiveness that is used to evaluate floor impact sound performance. Floor impact sound level of small-size specimen is higher than full-size. This is due to excessive impact power of Bang machine. Impact hammer that has small impact power relatively can solve this problem. But, according to the size of specimen, mode shape and frequency that influence to structural borne sound is changed. Slab mode of full-size specimen was changed to frequency design of resilient materials. But in case of small-size specimen, there is no change of vibration mode by resilient materials change, Vibration mode of small-size specimen is the same. Therefore, it is not proper that use small-size specimen in floor impact sound estimation.

The Design of Parameters to Improve Actuating Performance in High Frequency Vibro-Hammer(HFVH) and the Study of Characteristic Propagation and Attenuation of Piling Vibration (초고주파 진동항타기의 구동 성능향상을 위한 파라미터 설계 및 항타진동의 전달과 감쇠특성에 관한 연구)

  • Jang, Tae-In;Park, Joon-Hyuk;Baek, Yoon-Su;Kim, Sung-Bae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.6
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    • pp.763-773
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    • 2004
  • This paper suggests the 2 D.O.F mathematical model of the High Frequency Vibro-Hammer (HFVH), introduces an experimental method for measuring of the attenuation of piling vibration and proves what experiments are coincident with the equation of wave propagation. As vibratory installation of piles and casings has many economic merits in the construction field, most of all contractors prefer to vibratory pile driving method than the other. Compared to impact pile driving, vibratory installation has the advantage of reducing vibration or noise pollution and can drive piles under high frequency. Experiments serve estimations of capabilities and limitations of the HFVH's excitation force and finding of sensitivity for important soil resistance parameters. Also, we discuss the HFVH that can drive with three kinds of input waves (triangular, sine and square wave) and propose the design of parameters to improve actuating performance in it.

Study on the Fractures Types of PHC Pile by Impact Load of Follower (보조말뚝의 충격하중에 의한 PHC말뚝의 파손유형 고찰)

  • Seo, Dong-Nam;Choi, Sang-Ho;Kim, Jin-Sik;Kim, Min-Kab;Lee, Dong-Hyeon;Cho, Seong-Jun
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2021.11a
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    • pp.144-145
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    • 2021
  • This study analyzed the cases of cracks in piles due to the use of followers under construction conditions where water exists inside the piles, and confirmed whether the piles were cracked through a field test simulating the construction conditions in which water pressure inside the piles was generated by a hammer. According to the construction case, under the construction condition where the pile length is 20% to 30% shorter than the drilled length, about 80% cracks occur, so there is a high possibility of cracking due to water inside the pile. A field test was conducted to confirm the type of pile failure due to hammer under the construction condition in which water exists inside the pile. The pile head was not destroyed by the compressive load, and one or more longitudinal cracks occurred along the PC steel wire. The closed end pile generates water pressure by hammer. the follower and cushion(compression plywood) must be drilled at least 0.4D. It is expected that improved quality control will be possible as the water pressure inside the pile is reduced.

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Development of Acoustic Resonance Evaluation System to Detect the Welding Defects (용접 불량 검사를 위한 음향공진 검사 장치 개발)

  • Yeom, Woo Jung;Kim, Jin Young;Hong, Yeon Chan;Kang, Joonhee
    • Journal of Sensor Science and Technology
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    • v.28 no.6
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    • pp.371-376
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    • 2019
  • We have developed an acoustic resonance inspection system to inspect the welding defects in the mechanical parts fabricated using friction stir welding method. The inspection system was consisted of a DAQ board, a microphone sensor, an impact hammer, and controlled by a PC software. The system was developed to collect and analyze the sound signal generated by hitting the sample with an impact hammer to determine whether it is defective. In this study, 100% welded good samples were compared with 95%, 90%, and 85% welded samples, respectively. The variation of the completeness in welding did not affect the visual appearance in the samples. As a result of analyzing the natural frequencies of the good samples, the five natural frequency peaks were identified. In the case of the defective samples, the frequency change was observed. The welding failure detection time was fast enough to be only 0.7 seconds. Employing our welding defect inspection system to the actual industrial field will maximize the efficiency of quality inspection and thus improve the productivity.

Study on Analysis Process for Slip Torque Design Control of Impact Hammer Drills (임팩트햄머 드릴의 슬립토크 설계 제어를 위한 분석 프로세스 고찰)

  • Kim, Seung Hyeon;Kwon, Sang Youp;Ko, Dong Shin;Hur, Deog Jae;Dong, Kwang Ho
    • Journal of the Korean Society for Precision Engineering
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    • v.33 no.5
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    • pp.401-407
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    • 2016
  • This paper describes the derivation methodology of the working torque predictive model that can be used in the initial design stages of the impact hammer tool. The working torque control mechanism is designed, taking into account various factors, such as the force of the spring and friction. Firstly, the analysis dynamic model for working environments was modeled as an additional bush and spring, and verified by comparing the test results of the working torque. Secondly, the main performance parameters of the working torque were theoretically defined by analyzing the operating mechanism. The equation to predict the working torque was derived using the dynamic analysis results according to the value changes of the parameters. The prediction equation of the working torque was validated by comparing the predicted results with the experimental data. The error difference between the experimental data and the predictive model results was found to be 8.62%.