• Title/Summary/Keyword: Striker

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An Experimental Study on the Absorbed Energy of Polymeric Foam According to Different Mass and Impact Velocity Based on the Constant Impact Energy (동일 에너지 조건하에 충격체 질량과 속도변화에 따른 발포 고분자의 흡수 에너지에 관한 실험적 연구)

  • Kim, Byeong-Jun;Kim, Han-Kook;Cheon, Seong S.
    • Composites Research
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    • v.27 no.2
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    • pp.42-46
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    • 2014
  • In the present study, impact tests were carried out to investigate the crashworthy behaviour of the expanded polypropylene under the constant incident energy (100 J and 200 J) with five different combinations of striker mass and velocity. Also, preliminary quasi-static test was performed to obtain basic characteristics of the expanded polypropylene. MTS 858 and Instron dynatup 9250 HV were used for the quasi-static test and impact tests, respectively. In consequence, it was found that the impact energy absorption characteristics of the expanded polypropylene was more influenced by the striker mass instead of the velocity of the striker.

A Study on Improving the Impact Force of Impact Hammer Drill (충격햄머드릴의 타격력 향상을 위한 연구)

  • 김재환;정재천;박병규;백복현
    • Journal of KSNVE
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    • v.7 no.4
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    • pp.669-679
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    • 1997
  • This paper deals with a study of striker type impact hammer drill for improving the drilling performance. The study was performed through a numerical simulation of the impact hammer mechanism and an experimental comparison of the numerical simulation results was followed. Optimization of the impact mechanism was also performed. The numerical model of the impact hammer drill takes into account the striker motion and the effects of the pressure in the cylinder as well as the friction acting on the striker. The equation of motion is solved with the pressure equation in the cylinder including the friction force. The friction is considered as a combination of Coulomb friction and viscous damping friction. At the moment of impact, an ideal impact model that uses restitution coefficient is used to calculate the sudden change of the striker motion. The numerically simulated impact force shows a good agreement with the experimental result and thus, the validity of the numerical model is proven. Based upon the proposed model, an optimization was performed to improve the impact force of the hammer drill. The objective function is to maximize the impact force and the used design variables are striker mass, frequency of piston, bit guide mass, cylindrical diameter and dimensions of the mechanism components. Each design variable and some other conditions that are essential to manitain normal operation of the hammer drill are considered as constraints. The optimized result show a remarkable improvement in impact force and an experimental proof was investigated.

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Modeling and Design of Impact Hammer Drill (충격햄머드릴의 기구해석 및 설계)

  • 박병규;김재환;백복현;정재천
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1997.04a
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    • pp.146-152
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    • 1997
  • This paper deals with a study of striker type impact hammer drill for improving the drilling performance. The study was performed through a numerical simulation of the impact hammer mechanism, an experimental comparison of the numerical simulation results and an optimization of the impact mechanism. The numerical model of the impact hammer drill takes into account the striker motion and the effects of the pressure in the cylinder as well as the friction acting on the striker. The equation of motion is solved with the pressure equation in the cylinder and the friction force. At the moment of impact, an ideal impact model that uses restitutiion codfficient is used to calculate the sudden change of the striker motion. The impact force numerically simulated shows a good agreement with the experimental results and thus, the validity of the numerical model is proven. Based upon the proposed model, an optimization was performed to improve the impact force of the hammer drill. The objective function is to maximize the impact force and the design variables are striker mass, frequency of piston, bit guide mass, cylindrical diameter and dimensions of the mechanism components. Each design variable and some other conditions that are essential to maintain normal operation of the hammer drill are considered as constraints. The optimized result shows remarkable improvement in impact force and an experimental proof was investigated.

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Adaptation of impactor for the split Hopkinson pressure bar in characterizing concrete at medium strain rate

  • Zhao, Pengjun;Lok, Tat-Seng
    • Structural Engineering and Mechanics
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    • v.19 no.6
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    • pp.603-618
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    • 2005
  • The split Hopkinson pressure bar (SHPB) technique is widely used to characterize the dynamic mechanical response of engineering materials at high strain rates. In this paper, attendant problems associated with testing 70 mm diameter concrete specimens are considered, analysed and resolved. An adaptation of a conventional solid circular striker bar, as a means of achieving reliable and repeatable SHPB tests, is then proposed. In the analysis, a pseudo one-dimensional model is used to analyse wave propagation in a non-uniform striker bar. The stress history of the incident wave is then obtained by using the finite difference method. Comparison was made between incident waves determined from the simplified model, finite element solution and experimental data. The results show that the simplified method is adequate for designing striker bar shapes to overcome difficulties commonly encountered in SHPB tests. Using two specifically designed striker bars, tests were conducted on 70 mm diameter steel fibre reinforced concrete specimens. The results are presented in the paper.

A Study on the Development of Progressive Die and Forming Process for Asymmetric Automotive Door Striker (자동차용 비대칭 스트라이커의 순차이송금형 및 공정 개발에 관한 연구)

  • Youn, Jae-Woong;Kim, Hong-Seok
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.21 no.1
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    • pp.167-174
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    • 2012
  • For high production rate of parts requiring multiple operations such as punching, blanking, or other operations are generally done with progressive dies. However, progressive die is generally limited to use for sheet metal forming due to the technical difficulties in rod or bulk material. This study proposes a new technique of progressive die and forming process for asymmetric automotive door striker, which is conventionally manufactured with separate tandem processes using solid rod. In order to design forming process and die, FEM simulation was performed to divide proper intermediate processes and analyze its formability. As a result, Forming processes were divided into 3 stages with upper and side punches and also, workpiece feeding and location mechanism was designed and manufactured in this study. Finally, forming tryouts were carried out by using the manufactured progressive die to verify the forming quality and productivity.

Analysis of acceleration and deceleration of female hockey players using GPS (GPS를 활용한 여자 하키 선수들의 가속과 감속 분석)

  • Park, Jong-Chul;Kim, Ji-Eung;Choi, Eun-Young
    • Journal of Digital Convergence
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    • v.18 no.6
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    • pp.495-500
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    • 2020
  • This study was intended to quantify the acceleration and deceleration information measured in the competition by using GPS device for the national women's field hockey players and to identify the difference in movement by classifying them by position. For this study, 308 acceleration and deceleration data were collected from 16 women's field hockey players measured at international competitions. According to research results, the frequency of acceleration was in the order of midfield > defender > striker, acceleration distance was midfield > striker > defender. The frequency of deceleration appeared in the order of midfield > defender > striker, deceleration distance was defender > striker > defender. Based on the results of this study, can be used as basic data when setting the strength and amount of training for field hockey players.

Species Identification and Weathering of Wooden Striker on the Divine Bell of King Songdok (성덕대왕신종(聖德大王神鍾) 당목(撞木)의 수종(樹種)과 열화(劣化))

  • Kang, Aekyung
    • Conservation Science in Museum
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    • v.4
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    • pp.71-78
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    • 2003
  • The wooden striker on the Divine Bell of King Seongdeok was examined to identify the species of the wood and the outdoor wood weathering caused by solar light, moisture, temperature and air. The species of the wooden striker was identified to Zelkova serrata. When observed the striker with naked eyes, the results were surface discoloration (graying), cracking and roughness. In order to examine the morphological changes according to deterioration type, the specimen were separated to three part(I, II,III-spot). The I-spot was discolored to gray and at the same time entirely covered with dust. So the observation was impossible. The II-spot was also discolored but its texture could be observed. On it could observe numerous fungal hypae and dirts like dust flown into the cell lumens. The cell wall has been so weakened by weathering that it lost the physical intensity. This have made microchecks and splits on the cell wall. Although fungal hypae covered the cell, they did not result in wood decay. The III-spot, located just 0.5 mm below the surface, was maintaining the natural red-brown color of the wood. Its cell wall was similar to that of sound wood. These changes are different from wood decay, and limited only to the surface of the striker-less than or equal to 0.5 mm below.

Experimental Investigations on the Plastic Damage of Plates due to Lateral Collisions

  • Cho, Sang-Rai;Kim, Il-Woong;Lee, Sang-Bock
    • Journal of Ship and Ocean Technology
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    • v.6 no.3
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    • pp.1-12
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    • 2002
  • In this paper the results are reported of sixty-nine lateral collision tests, which were performed to investigate the collision resistance of plates. For the tests a collision testing machine of spring-roller conveyer type was designed and fabricated. Using this machine, various plates were tested with different masses and velocities and various headers of the striker. A simple analytical method has also been developed to predict the extent of damage of struck plates due to lateral collision. In the method, it is assumed that the kinetic energy of the striker can be dissipated by the formation of yield lines and membrane tensions in the impacted plate. The calculated predictions of extent of damage using the developed method have been substantiated with the test results, which shows reasonably acceptable correlations.

Analysis on the Impact of Composite by Using FEM (유한요소법을 이용한 복합재료의 충격에 관한 해석)

  • Kim, Sung-Soo;Kim, Young-Chun;Hong, Soon-Jik;Kook, Jeong-Han;Kim, Sei-Hwan;Cho, Jae-Ung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.2
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    • pp.542-547
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    • 2013
  • In this study, mechanical property on the composite material of aluminum foam core is investigated by simulation analysis. Impact energies such as 50J, 70J, and 100J are applied to the specimen model. The maximum load occurs at 3.4ms for 50J, 3.2ms for 70J, and 3.2ms for 100J respectively. The striker penetrates the upper face sheet, causing the core to be damaged at 50J test but the lower face sheet remains intact with no damage. It results in occurring with the energy of 52 J. At 70J test, it penetrates the upper face sheet and penetrated the core. And the striker causes the lower face sheet with damage. And it results in occurring with the energy of 65 J. Finally at 100J test, the striker penetrated both the upper face sheet and core and even the lower face sheet. The load becomes maximum at the time when striker penetrates through the upper plate and it rapidly reduced. And then the load increases rapidly when reaching the lower face sheet. And it decreases again. It results in occurring with the energy of 95 J.

SHPB Tests for Rock Dynamic Behavior by Shock Loading (충격하중에 의한 암석의 동적거동 측정시험장치)

  • Park, Chul-Whan;Park, Eui-Seob
    • Tunnel and Underground Space
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    • v.20 no.5
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    • pp.318-324
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    • 2010
  • Dynamic properties of materials by shock loads such as rock blasting and earthquake are recently attracted in the design of aboveground and underground structures. The advance of measuring devices enables to obtain the whole histories of stress and strain in rock specimen of which the failure is completed in several hundred microseconds. The SHPB has been a popular and promising technique to study the dynamic behavior of rock. And the dynamic compressive, tensile and other test with this experiment system are planned to be Suggested Methods of ISRM. This technical paper is to introduced one study article which focuses the design of 3S (special shaped striker) to produce the half-sine wave to eliminate the problems of the rectangular wave. This article is also describing the advantage of half-sine incident wave and size effect of rock dynamic strength.