• Title/Summary/Keyword: steel specimen

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True Stress-True Strain Curves Obtained by Simulating Tensile Tests Using Finite Element Program (인장시험을 유한요소해석 시뮬레이션하여 진응력-진변형도 곡선을 결정하는 방법)

  • Chu, Seok-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.1
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    • pp.25-31
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    • 2011
  • In the tensile test necking occurs at the maximum load point and non-uniform stress state is generated in this section. The equivalent stress becomes quite different from the axial stress as necking proceeds. Methods for obtaining the true stress-true strain curves, by overcoming difficulties due to the necking phenomena, have been developed by many authors. One of the methods based on the finite element analysis simulation is a very promising method. In this paper, general-purpose finite element program is used to simulate the tensile test. A round specimen and a flat specimen prepared from the same steel block are tested and simulated. The true stress-true strain curves are determined without assuming that the material follows Hollomon's law.

Fire Resistance Performance for Fiber Reinforced High Strength Concrete Column Member (폴리프로필렌 및 강섬유 보강 고강도 콘크리트 기둥부재의 내화성능)

  • Jang, Chang-Il;Lee, Sang-Woo;Choi, Min-Jung;Kim, Joon-Mo;Kim, Heung-Youl;Won, Jong-Pil
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.457-460
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    • 2008
  • This study evaluated fire resistance performance for polypropylene/steel fiber reinforced high strength concrete column. Full-size columns were constructed and tested with or without fibers using ISO-834 fire curve. As the result of test, non-fiber high strength concrete column specimen occurred serious spalling and indicated rapidly internal temperature increase. Specimen with polypropylene fiber occurred not spalling. Specimen with hybrid fiber occurred not spalling as well as does not propagated temperature propagation. Therefore, hybrid fiber reinforced column specimen indicated a good fire resistance performance than other cases.

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Fatigue Crack Propagation Behavior of Steel Plate of Laser Welded Tailored Blank (테일러드 블랭크 레이저 용접 강판의 피로균열 전파 거동)

  • Han, Moon-Sik;Lee, Yang-Sub
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.15 no.3
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    • pp.120-126
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    • 2006
  • In this paper, we investigated the characteristics of fatigue fracture on TB(Tailored Blank) weldment by comparing the fatigue crack propagation characteristics of base metal with those of TB welded sheet used for vehicle body panels. We also investigated the influence of center crack on the fatigue characteristic of laser weld sheet of same thickness. We conducted an experiment on fatigue crack propagation on the base metal specimen of 1.2mm thickness of cold-rolled metal sheet(SPCSD) and 2.0mm thickness of hot-rolled metal sheet(SAPH440) and 1.2+2.0mm TB specimen. We also made an experiment on fatigue crack propagation on 2.0+2.0mm and 1.2+1.2mm thickness TB specimen which had center crack. The characteristics of fatigue crack growth on the base metal were different from those on 1.2+2.0mm thickness TB specimen. The fatigue crack growth rate of the TB welded specimens is slower in low stress intensity factor range$({\Delta}K)$ region and faster in high ${\Delta}K$ region than that of the base metal specimens.

Structural Behavior of Two-Seam Cold Formed Square CFT Column to Beam Connections (2심 냉간성형 각형 CFT기둥-보 접합부의 구조거동)

  • Oh, Heon-Keun;Kim, Sun-Hee;Park, Chan-Myun;Choi, Sung-Mo
    • Journal of Korean Association for Spatial Structures
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    • v.12 no.4
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    • pp.81-90
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    • 2012
  • The concrete-filled tube (CFT) column has the excellent structural performance. But it is difficult to connect with column and beam because of closed section. Its Solution, 2 members of ㄷchennel in which Internal diaphragm is installed were welded beforehand and the method of making Rectangular Steel Tube was proposed. According to upside and downside junction shape, Internal diaphragm suggested as symmetric specimen and asymmetric specimen. The upper and lower diaphragm of the Symmetric specimen used the same horizontal and The upper diaphragm of the Asymmetric specimen used the horizontal plate and the lower diaphragm used the vertically plate. In this research, 4 T-shape column to beam steps connections were tested with cyclic loading experiment in order to evaluate the structural capability of the offered connection. Symmetric specimens be a failure in 0.03rad from beam flange. And Asymmetric specimens be a failure in 0.05rad from column interface. The comparison results of All specimens shown similar to energy absorption capacity in 0.02rad.

Interface treatment in shotcrete jacketing of reinforced concrete columns to improve seismic performance

  • Vandoros, Konstantinos G.;Dritsos, Stephanos E.
    • Structural Engineering and Mechanics
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    • v.23 no.1
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    • pp.43-61
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    • 2006
  • An investigation of the effectiveness of the interface treatment when column concrete jacketing is performed is presented. Alternative methods of interface connection were used in order to investigate the performance of strengthened concrete columns. These connecting techniques involved roughening the surface of the original column, embedding steel dowels into the original column and a combination of these two techniques. The experimental program included three strengthened specimens, one original specimen (unstrengthened) and one as-built specimen (monolithic). The specimens represented half height full-scale old Greek Code (1950's) designed ground floor columns of a typical concrete frame building. The jackets of the strengthened specimens were constructed with shotcrete. All specimens were subjected to displacement controlled earthquake simulation loading. The seismic performance of the strengthened specimens is compared to both the original and the monolithic specimens. The comparison was performed in terms of strength, stiffness and hysteretic response. The results demonstrate the effectiveness of the strengthening methods and indicate that the proper construction of a jacket can improve the behaviour of the specimens up to a level comparable to monolithic behaviour. It was found that different methods of interface treatment could influence the failure mechanism and the crack patterns of the specimens. It was also found that the specimen that combined roughening with dowel placement performed the best and all strengthened columns were better at dissipating energy than the monolithic specimen.

Hysteretic Behavior of Precast Concrete Large Panel Structures Subjected to Horizontal Cyclic Loading (반복 횡하중을 받는 프리캐스트 대형 콘크리트 판구조의 이력특성에 관한 실험적 연구)

  • Seo, Soo-Yeon;Yi, Waon-Ho;Lee, Li-Hyung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.3 no.3
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    • pp.253-260
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    • 1999
  • Main objective of this study is to examine the hysteretic behaviors and to evaluate the capacity of precast concrete (PC) large panel structures simulated from the prototype of 15-story building, Two 1/2 scaled precast concrete wall specimens and one monolithic reinforced concrete specimen were designed and tested under the cyclic loading conditions. The main parameter of test specimens in PC large panel structure is the type of details for vertical continuity of vertical steel in horizontal joint. Also the behaviors of PC large panel structures are compared with that of monolithic reinforcement concrete wall structure. From the results, the stiffness and energy dissipation ratio of the precast concrete specimens are shown little bit lower than those of monolithic reinforced concrete specimen. In the PC large panel structures, the specimen connected vertically by welding (strong connection) showed higher strength than that of the specimen connected vertically by joint box. However the failure pattern of the former showed more brittle than that of the latter due to the diagonal compressive failure of wall panels.

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Fatigue Behavior of Prestressed Concrete Beams Using FRP Tendons (FRP 긴장재를 이용한 프리스트레스트 콘크리트 보의 피로 거동)

  • Kim, Kyoung-Nam;Park, Sang-Yeol;Kim, Chang-Hoon
    • Journal of the Korea Concrete Institute
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    • v.23 no.2
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    • pp.135-144
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    • 2011
  • Recently, researches about fiber reinforced polymer (FRP) which has excellent durability, corrosion resistance, and tensile strength as a substitution material to steel tendon have been actively pursued. This study is performed to examine FRP tendon used prestressed beam's safety under service load. The specimen was a prestressed concrete beam with internal bonded FRP tendon. In order to compare the member fatigue capacity, a control specimen of a prestressed concrete beam with ordinary steel tendon was tested. A fatigue load was applied at a load range of 60%, 70%, and 80% of the 40% ultimate load, which was obtained though a static test. The fatigue load was applied as a 1~3 Hz sine wave with 4 point loading setup. Fatigue load with maximum 1 million cycles was applied. The specimen applied with a load ranging between 40~60% did not show a fatigue failure until 1 million cycles. However, it was found that horizontal cracks in the direction of tendons were found and bond force between the tendon and concrete was degraded as the load cycles increased. This fatigue study showed that the prestressed concrete beam using FRP tendon was safe under a fatigue load within a service load range. Fatigue strength of the specimen with FRP and steel tendon after 1 million cycles was 69.2% and 59.8% of the prestressed concrete beam's static strength, respectively.

The Effect of Atmospheric Plasma Parameters on Cleansing the Electronic-Industrial Parts (상압 플라즈마 매개변수들이 산업용 전자부품의 세척공정(cleansing)에 미치는 효과)

  • Ri, Eui-Jae
    • Journal of Surface Science and Engineering
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    • v.42 no.5
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    • pp.208-215
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    • 2009
  • We employed atmospheric plasma to reactively remove the lubricant sprayed onto such industrial electronic parts as LCD chassis during sheet-metal forming processes and investigated basically the effect of plasma parameters on cleansing the surfaces of zinc-electroplated steel plates (EGI). Specimen prepared with some controlled amount of lubricant sprayed on their surfaces beforehand were subjected to two different kinds of atmospheric plasma, one being generated by using air and the other generated by using nitrogen (99.9% purity). Locating the plasma beams at the height range between 3.5 and 13.5 mm from the surface of each specimen and radiating for 5 to 30 seconds resulted out that the cases with a position of 3.5 mm and a duration of 5 seconds or longer showed the surfaces completely cleansed without a trace of lubricant. Furthermore we found out that the plasma generated by using simple air depicted higher cleansing ability than the other one generated by using expensive nitrogen, interestingly useful very much for industrial purposes. On another aspect, we confirmed that the drilled or cut surfaces of Zn-plated steel substrate would not be oxidized even under the influence of plasma during its cleansing process. Therefore, we could probably conclude from this fore-survey that a dry process adopting atmospheric plasma for cleansing industrial parts might be determined to become successful in terms of commercialization, cautiously.

Evaluation on fracture toughness of high frequency electric resistance welded steel pipe by unloading compliance method (고주파 전기저항 용접강관의 제하 컴플라이언스법에 의한 파괴인성 평가)

  • 오세욱;윤한기;안광주
    • Journal of Welding and Joining
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    • v.5 no.2
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    • pp.44-52
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    • 1987
  • The fracture toughness, $J_{IC}$ of high frequency electric resistance welded steel pipe for smooth and side-grooved CT specimen was evaluated by unloading compliance method. The crack growth, .${\delta}a$ was obtained from the equation of Donald and Saxena & Hudak, and $J_{IC}$ was determined from the curve of J-${\delta}a$ relations. The crack growth on the experiment using unloading compliance method is underestimated as compared with ${\delta}a$ measured directly by the SEM, so the reliability of $J_{IC}$ from saxena & Hudak equation is large than that from Donald. The $J_{IC}$ value of side-grooved CT Specimen is estimated less than that of smooth, and this is the effect of the side-groove, the shear-lip of crack tip and the reduction of crack tunnelling phenomena.

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A Study on Corrosive Behavior of Spring Steel by Shot-Peening Process (쇼트피닝 가공을 통한 스프링강의 부식거동에 관한 연구)

  • An, Jae-Pil;Park, Keyung-Dong
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.325-330
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    • 2004
  • Recently, the request for the high strength of material is more and more increased in the area of industrial environment and machinery. To accomplish the high strength of materials, carbonizing treatment, nitrifying treatment, shot-peening method are representatively applied, however, shot-peening method is generally used among the surface processes. Shot peening is a cold working process used to impact Compressive residual stressed in the exposed surface layers. Benefits due to shot peening are increase in resistance to fatigue, stress corrosion cracking, fretting, galling, erosion and closing of pores. In this study, the influence of shot peening on the corrosion was investigated on spring steel immersed in 3.5% NaCl. The immersion test as performed on the two kinds of specimens. Corrsion potential, polarization curve, residual stress and etc, were investigated from experiment results. From test result the effect of shot peening on the corrosion was evaluated. The important results of the experimental study on the effects of shot peened on the environment corrosion of spring steels are as follows; In case of corrosion potential, shot peened specimen shows more activated negative direction as compared with parent mental. Surface of specimen, which is treated with the shot peened is placed as more activated state against inner base metal. It can cause t도 anti-corrosion effect on the base metal.

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