• Title, Summary, Keyword: crack resistance property

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Behavior of optimized prestressed concrete composite box-girders with corrugated steel webs

  • Lu, Yanqiu;Ji, Lun
    • Steel and Composite Structures
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    • v.26 no.2
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    • pp.183-196
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    • 2018
  • The traditional prestressed concrete composite box-girders with corrugated steel webs have several drawbacks such as large deflection and potential local buckling. In this study, two methods were investigated to optimize and improve the prestressed concrete composite box-girders with corrugated steel webs. The first method was to replace the concrete bottom slab with a steel plate and the second method was to support the concrete bottom slab on the steel flanges. The behavior of the prestressed concrete composite box-girders with corrugated steel webs with either method was studied by experiments on three specimens. The test results showed that behavior of the optimized and upgraded prestressed concrete composite box-girders with corrugated steel webs, including ultimate bearing capacity, flexural stiffness, and crack resistance, is greatly improved. In addition, the influence of different shear connectors, including perfobond leisten (PBL) and stud shear connectors, on the behavior of prestressed concrete composite box-girders with corrugated steel webs was studied. The results showed that PBL shear connectors can greatly improve the ultimate bearing capacity, flexural stiffness and crack resistance property of the prestressed concrete composite box-girders with corrugated steel webs. However, for the efficiency of prestressing introduced into the girder, the PBL shear connectors do not perform as well as the stud shear connectors.

Effects of Cr Content and Volume Fraction of δ-Ferrite on Thermal Cycling Fatigue Properties of Overlay Welded Heat-Resistant 12%Cr Stainless Steels (내열용 오버레이 12%Cr계 스테인레스강의 열피로 특성에 미치는 Cr 함량과 델타-페라이트의 영향)

  • Jung, J.Y.
    • Transactions of Materials Processing
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    • v.26 no.6
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    • pp.356-364
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    • 2017
  • In this study, submerged arc cladded Fe-Cr-Ni-Mo-CuWNbV-C stainless steels containing various Cr contents between 11.2 wt.% and 16.7 wt.% were prepared with fixed C content at about 0.14 wt.%. Using these alloys, changes in microstructure, tensile property, and thermal fatigue property were investigated. Phase fraction of delta-ferrite was increased gradually with increasing Cr content. However, tensile strength, hardness, and thermal fatigue resistance appeared to be decreased. When the microstructure of delta-ferrite was observed, it was revealed that the mesh structure retained up to about 15% Cr content. Although thermal fatigue resistance was almost the same for Cr contents between 11.0 and 14.5 wt.%, it was significantly decreased at higher Cr contents. This was evident from mean value of crack lengths of 10 largest ones. Evaluation of thermal fatigue resistance on alloys with various Cr contents revealed the following important results. First, the reproducibility of ranking test was excellent regardless of the number of cycles. Second, thermal fatigue resistance was increased in proportion to true tensile fracture strength values of overlay materials. Finally, the number of thermal fatigue cracks per unit length was increased with increasing true tensile fracture strength.

A Study on Mechanical Property and Fatigue Crack Growth Behavior of Surface-Hardened SM53C Steel (표면 경화된 SM53C의 기계적 특성 및 피로균열진전 거동해석에 관한 연구)

  • Kim, Hwang-Soo;Kim, Jung-Hyun;Jeon, Hyun-Bae
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.9 no.4
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    • pp.44-52
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    • 2010
  • Recently, with the high performance and efficiency of machine, there have been required the multi-functions in various machine parts, such as the heat resistance, the abrasion resistance and the stress resistance as well as the strength. Fatigue crack growth tests were carried out to investigate the fatigue characteristics of high carbon steel (SM53C) experienced by high-frequency induction treatment. The influence of high-frequency induction treatment on fatigue limit was experimentally examined with the specialfocus on the variation of surface microstructure and the fatigue crack initiation and propagation through fractography. Also, the shape of hardening depth, hardened structure, hardness, and fatigue-fracture characteristics of SM53C composed by carbon steel are also investigated.

Effect of Corrosion on Fatigue Life of Piping material under Repeating Load (반복하중을 받는 배관용 강재의 피로수명에 미치는 부식의 영향)

  • Park, Keyung-Dong;An, Jae-Pil
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • pp.228-229
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    • 2005
  • The compressive residual stress, which is induced by shot peening process, has the effect of increasing the intrinsic fatigue strength of surface and therefore would be beneficial in reducing the probability of fatigue damage. However, it was not known that the effect of shot peening in corrosion environment. In this study, the effect of shot peening on corrosion fatigue crack growth of sping steel immersed in 6% $FeCl_3$ solution and corrosion characteristics with considering fracture mechanics. The results of the experimental study corrosion fatigue characteristics of spring steel are as follows; the fatigue crack growth rate of the shot peening material was lower than of the un peening material. And fatigue life shows more improvement in the shot peening material than un peening material. This is because the compressive residual stress of surface operate resistance of corrosion fatigue crack propagation. It is assumed that the shot peening process improve corrosive resistance and mechanical property.

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A Study on the Bottom Design of Petaloid Carbonated PET Bottle to Prevent Bottom Crack (탄산음료용 PET병의 바닥면 크랙방지를 위한 Petaloid 디자인)

  • Shin H. C.;Lyu M. Y.;Kim Y. H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.154-157
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    • 2001
  • Through this study we investigated the causes of bottom crack. We then redesigned petaloid bottom to prevent bottom crack. We examined the material property variations according to the stretch ratio of PET and analyzed stretches of bottom in blowing processes. We also performed crack test to observe a crack phenomena. The effective stress and maximum principal stress were examined by computer simulation. We concluded that the bottom crack occurs because of not only insufficient strength of material due to the insufficient stretch of PET but also coarse design of petaloid shape. The highest maximum principal stress occurred at valley in petaloid bottom of bottle and this strongly affected the crack in bottom. We redesigned petaloid shape to minimize maximum principal stress, and this result in increasing the crack resistance.

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A study on the Relation between Strain & Conductivity of the Printed Pattern in Post-Printing Section of Roll to Roll process (롤투롤 공정의 인쇄 후 구간에서 변형률과 인쇄한 패턴의 전기 전도도와의 관계에 대한 연구)

  • Choi, Jae-Ho;Lee, Chang-Woo;Shin, Kee-Hyun
    • Journal of Institute of Control, Robotics and Systems
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    • v.15 no.9
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    • pp.877-880
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    • 2009
  • A curing process in post-printing section of R2R process is required for an electrical property of the printed pattern when devices such as RFID, Solar cell are printed. PEN as well as heat-stabilized PET which is used as a plastic substrate would be deformed at high temperature due to change of its elastic modulus. And crack in the printed pattern, which is on the plastic substrate is occurred due to the deformation of the substrate. The occurrence of crack causes electrical resistance to increase and the quality of the device to deteriorate. In case of RFID antenna, the range of reading distance is shortened as the electrical resistance of the antenna is increased. Therefore, the deformation of the plastic substrate, which causes the occurrence of crack, should be minimized by setting up low operating tension in R2R process. In low tension, slippage between a moving substrate and a roller would be generated when the operating speed is increased. And scratch would be occurred when slippage is generated due to an air entrainment, which is related to the thickness of the air film. The thickness of the air film is increased when operating speed is increased as shown by simulation based on mathematical model. The occurrence of scratch in conductive pattern printed by roll to roll process is a critical damage because it causes degradation or failure of electrical property of it.

High Strength Low Alloy Steel for Sour Service

  • Jung, Hwan Gyo;Kim, Sang Hyun;Yang, Boo Young;Kang, Ki Bong
    • Corrosion Science and Technology
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    • v.7 no.5
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    • pp.288-295
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    • 2008
  • The increase use of natural gas as an energy source has been continuous demand for ever-increasing strength in gas transmission pipeline materials in order to achieve safe and economic transportation of natural gas. In particular, linepipe material for sour gas service primarily needs to have crack resistant property. However, applications of sour linepipes are expanding toward deep water or cold region, which require higher toughness and/or heavier wall thickness as well as higher strength. To improve the crack resistance of linepipe steel in sour environment, low alloy steel are produced by controlled rolling subsequently followed by the accelerated cooling process. This paper summarizes the design concepts for controlling crack resistant property low alloy linepipe steels for sour gas service.

The Effect of Temperature, Frequency and Microstructure on Fatigue Crack Propagation in Ti-6A1-4V Alloy (Ti-6A1-4V 합금의 피로거동에 미치는 온도, 주파수 및 미세조직의 영향)

  • 김현철;김승한;임병수;김두현;이용태
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.1
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    • pp.198-207
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    • 1996
  • The effect of temperature, frequency and microstructure on fatigue crack propagation property of Ti-6A1-4V alloy has been investigated. The temperatures employed were room temperature, 20$0^{\circ}C$ and 40$0^{\circ}C$. The frequencies were 20Hz and 8 Hz. The microstructures tested were equiaxed and bimodal microstructures. Mechanical properties and fatigue crack growth rates were measured in different test conditions. From the experimental results, following conclusions were obtained. Bimodal microstructure showed superior fatigue crack growth resistance to equiaxed microstructure. Under all test conditions, fatigue crack growth rate increased with test temperature. Wine the frequency decreasing from 20Hz to 8Hz, fatigue crack growth rate increased.

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An Effect of Shot Peening on Corrosion Fatigue Crack Growth of Suspension Material (현가장치재의 부식피로균열진전에 미치는 쇼트피닝의 영향)

  • Park, Keyung-Dong;An, Jae-Pil
    • Transactions of the Korean Society of Automotive Engineers
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    • v.14 no.3
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    • pp.88-94
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    • 2006
  • The compressive residual stress, which is induced by shot peening process, has the effect of increasing the intrinsic fatigue strength of surface and therefore would be beneficial in reducing the probability of fatigue damage. However, the effect of shot peening in corrosion environment was not known. In this study, investigated is the effect of shot peening on corrosion fatigue crack growth of SAE 5155 steel immersed in 6% $FeCl_3$ solution and corrosion characteristics with considering fracture mechanics. The results of the experimental study corrosion fatigue characteristics of SAE 5155 are as follows; the fatigue crack growth rate of the shot peening material was lower than that of the non-peening material. And fatigue life shows more improvement in the shot peening material than in non-peening material. This is due to the compressive residual stress of surface increases resistance of corrosion fatigue crack propagation. It is assumed that the shot peening process improve corrosive resistance and mechanical property.

An Experimental Study on the Shrinkage Properties and Resistance for Chloride Attack of Seaside Construction Concrete added Durability Improvement Agent (내구성개선제가 첨가된 해안 구조물용 콘크리트의 수축특성과 내염해성에 관한 실험적 연구)

  • Kim, Do-Su;Kim, Woo-Jae;Kim, Hyun-Bae;Jung, Sang-Jin
    • Proceedings of the Korean Institute of Building Construction Conference
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    • pp.151-154
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    • 2006
  • It is generally referred that life cycle of concrete construction is depend on whether durability of concrete is obtained or not. Nevertheless, it has not been yet applied that new material and technology to improve durability of concrete such as seaside concrete construction. In this study, chemical agent which is capable of improving durability added to 2 types seaside concrete mixs and evaluated engineering properties such as slump, air content, setting time and compressive strength. Besides shrinkage crack with an restraint condition and chloride ion penetration tests were executed to measure resistance of concrete added chemical agent and then compared non-added. It was appeared that engineering properties and resistant for chlorides was possible to improved. But resistant for shrinkage crack was not noticeable improvement than non-added. Therefore it is necessary that more consideration and following study to improve durability aspect to shrinkage crack and chlorides resistant.

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