• Title/Summary/Keyword: Crack Width

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Flexural Behavior of Composite Ring Stiffened by GFRP and Steel Pipe (GFRP와 강관으로 구성된 합성형 보강링의 휨거동)

  • Yoon, A Reum;Kim, Su Eun;Kim, Sung Bo
    • Journal of Korean Society of Steel Construction
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    • v.29 no.1
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    • pp.61-71
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    • 2017
  • The flexural behavior of composite ring stiffened by GFRP and steel pipe is presented in this paper. The effective width is required to construct FEM beam element model to verify the composite flexural behavior of stiffened ring of cylindrical shell structure. The experimental results are compared with the theoretical and FEM results by commercial program ABAQUS to verify the effective width coefficient. The yield, crack and ultimate loads is calculated using theoretical strains that varies depending on yield state and compared with experiment result and FEM results by ABAQUS solid model.

A Study on Structural Analysis of Reinforced Longitudinal Rib in Orthotropic Steel Deck Bridge (보강된 세로리브에 의한 강바닥판교의 응력변화 연구)

  • Kong, Byung-Seung;Kim, Min-Ho
    • Proceedings of the KSR Conference
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    • 2007.11a
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    • pp.468-475
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    • 2007
  • The Steel deck a structural analysis in head plate form change the objective bridge which it sells it accomplished a detailed structural analysis from the research which it sees and Bulk-head plate it accomplished. The length rib where the fatigue crack which is considerable generally occurs, width rib connection department and the length rib side, the width rib side it compares principal stress in the object and it does to sleep. It applied the grudge element model which it describes consequently after words and a load and a boundary condition and it executed it compared a static test and principal stress. It grasped the stress conduct of the The Steel deck petal which it follows in hand weaving rib affix location and the affix location to sleep in order to analyze a same location Bulk-head the head and comparison considered. From the detailed section which is reinforced with the stress investigation result hand weaving rib of the location which is weak in structural analysis result fatigue crack of form star reinforcement details basic form and Bulk-head the form which is reinforced with the head plate compared to principal stress investigation hour it is judged at the section which separates most.

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A Study on the Fatigue Crack Growth Characteristics of the Welded Part According to the Welding Method of Ship Structural Steel (선체구조용강의 용접방법에 따른 용접부의 피로균열전파특성 연구)

  • Park, Kyeong-Dong;Ki, Woo-Tae;Lee, Ju-Yeong
    • Journal of Advanced Marine Engineering and Technology
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    • v.31 no.4
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    • pp.385-393
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    • 2007
  • The strength evaluation of the most weakest junction part is required for the safety design of all structures. Most of all. in order to enhance the reliability and safety of the welding part. whose use is the highest, it is very important to establish the efficient structure manufacturing technology by studying and investigating the evaluation of fatigue strength in various environments. This study analyzed the relations of da/dN, and th according to the welding methods of SMAW, FCAW, and SAW. In the stage II. the value of stress intensity factor range was the highest in SMAW welding method of stress ration R=0.1, and appeared under the sequence of FCAW and SAW and as the completion section of stress intensity factor was low, threshold stress intensity factor was lowly formed in da/dN - The fatigue life of each welding method is sensitively worked in high stress ratio. judging from the fact that the width of life reduction increases in the high stress ratio zone compared to the width of life reduction in the low stress ratio zone. In the fatigue limit of welding methods before corrosion. the welding of SMAW and FCAW shows the same fatigue limit compared to Base metal, and SAW holds the lowest fatigue limit value.

Effects of Specimen Size in Evaluation of Elastic-Plastic Fracture Toughness by Ultrasonic Method (초음파법을 이용한 탄소성 파괴인성치 평가에 있어서 시험편 크기의 영향)

  • 강동명;함경춘;우창기
    • Journal of the Korean Society of Safety
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    • v.13 no.4
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    • pp.19-24
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    • 1998
  • Elastic-plastic fracture toughness($J_{IC}$) by ultrasonic method is evaluated in terms of width and thickness. Widths of specimen in 6061-T6 aluminum alloy are 50mm and 100mm, thicknesses of those are 20mm and 25mm, respectively. Elastic-plastic fracture toughness by ultrasonic method is independent of specimen thickness and side groove. Angle beam probe which are placed on the end of the compact specimen detect the maximum crack extension effectively. Comparing with elastic-plastic fracture toughness by ultrasonic method and that of unloading compliance method, $J_{IC}$ of ultrasonic method are underestimated to that of unloading compliance method. Elastic-plastic fracture toughness of width 100mm specimen are underestimated to that of width 50mm specimen about 20%.

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Study on the Crack Generation Patterns with Change in the Geometry of Notches and Charge Conditions (노치 형상 및 장약조건의 변화에 따른 균열발생양상에 관한 연구)

  • Park, Seung-Hwan;Cho, Sang-Ho;Kim, Seung-Kon;Kim, Kwang-Yeom;Kim, Dong-Gyou
    • Tunnel and Underground Space
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    • v.20 no.1
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    • pp.65-72
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    • 2010
  • Crack-controlled blasting method which utilizes notched charge hole has been proposed in order to achieve smooth fracture plane and minimize the excavation damage zone. In this study, the blast models, which have a notched charge hole, were analyzed using dynamic fracture process analysis software to investigate the effect of the geometry of a notched charge hole and decoupling indexes of the charge hole on crack growth control in blasting. As a result, crack extension increased and damage crack decreased with the notch length. Ultimately, stress increment factors and resultant fracture patterns with different notch length and width were analyzed in order to examine the effect factors on the crack growth controlling in rock blasts using a notched charge hole.

Improved ILDC Formulation for Very Thin Gap/Crack (아주 가는 균열의 산란 해석을 위한 향상된 ILDC 공식)

  • Lee, Hyunsoo;Koh, Il-Suek
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.25 no.9
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    • pp.938-943
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    • 2014
  • The scattered field by a gap/crack on the PEC surface of a large object having low-observable RCS cannot be negligible, but may not be analyzed by the known high-frequency technique. If the electrical width of the crack is very small, the crack can be modeled by an impedance strip, whose scattering formulation can be analytically obtained based on a low-frequency approximation. The scattering solution is formulated for the 2D strip and TE(Transverse Electric) or TM(Transverse Magnetic) wave incidence, from which a 3D ILDC(Incremental Length Diffraction Coefficients) can be extracted. Using the ILDC formulation, the scattering by any arbitrary shaped crack can be estimated. In this paper, an improved ILDC equations are proposed, which combine the known TE and TM solutions. The improved accuracy of the proposed solution is numerically verified.

Reliability Improvement of Offshore Structural Steel F690 Using Surface Crack Nondamaging Technology

  • Lee, Weon-Gu;Gu, Kyoung-Hee;Kim, Cheol-Su;Nam, Ki-Woo
    • Journal of Ocean Engineering and Technology
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    • v.35 no.5
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    • pp.327-335
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    • 2021
  • Microcracks can rapidly grow and develop in high-strength steels used in offshore structures. It is important to render these microcracks harmless to ensure the safety and reliability of offshore structures. Here, the dependence of the aspect ratio (As) of the maximum depth of harmless crack (ahlm) was evaluated under three different conditions considering the threshold stress intensity factor (Δkth) and residual stress of offshore structural steel F690. The threshold stress intensity factor and fatigue limit of fatigue crack propagation, dependent on crack dimensions, were evaluated using Ando's equation, which considers the plastic behavior of fatigue and the stress ratio. ahlm by peening was analyzed using the relationship between Δkth obtained by Ando's equation and Δkth obtained by the sum of applied stress and residual stress. The plate specimen had a width 2W = 12 mm and thickness t = 20 mm, and four value of As were considered: 1.0, 0.6, 0.3, and 0.1. The ahlm was larger as the compressive residual stress distribution increased. Additionally, an increase in the values of As and Δkth(l) led to a larger ahlm. With a safety factor (N) of 2.0, the long-term safety and reliability of structures constructed using F690 can be secured with needle peening. It is necessary to apply a more sensitive non-destructive inspection technique as a non-destructive inspection method for crack detection could not be used to observe fatigue cracks that reduced the fatigue limit of smooth specimens by 50% in the three types of residual stresses considered. The usefulness of non-destructive inspection and non-damaging techniques was reviewed based on the relationship between ahlm, aNDI (minimum crack depth detectable in non-destructive inspection), acr N (crack depth that reduces the fatigue limit to 1/N), and As.

Evaluation of the Bending Behavior of RC beam by Using Color-based Image Processing Method (색상에 기반한 영상분석기법을 이용한 콘크리트 거더의 휨 거동 분석)

  • Woo, Tae-Ryeon;Jung, Chi-Young;Kim, In-Tae;Lee, Jong-Han;Cheung, Jin-Hwan
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.24 no.4
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    • pp.48-54
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    • 2020
  • Cracks in reinforced concrete structures are the most common type of damage and are used as important analytical data to understand the fracture behavior characteristics of structures. Currently, there is a problem that most of the crack investigation relies on visual inspection, therefore many researchers have proposed image analysis techniques to improve the problem. In this study, we proposed a crack evaluation method to be applied at an indoor experimental level using image analysis method. The image analysis technique using color is for distinguishing a boundary surface between objects existing in an image, and is a method for separating similar colors into one region based on a predefined color. In this study, to improve the accuracy of image analysis, blue paint was applied to the concrete surface and bending experiments were performed. The image analysis method was able to measure the crack width with superior accuracy compared to the crack diameter, and at the same time, it was also possible to analyze the deflection of the beam. Both the crack and deformation were able to confirm the accuracy similar to the existing measurement method, and it was found that the image analysis method was very excellent in terms of applicability.

Ductile crack initiation evaluation in stiffened steel bridge piers under cyclic loading

  • Fujie, Wataru;Taguchi, Miki;Kang, Lan;Ge, Hanbin;Xu, Bin
    • Steel and Composite Structures
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    • v.36 no.4
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    • pp.463-480
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    • 2020
  • Although detailed shell analysis is suitable to predict the ductile crack initiation life of steel members, such detailed method adds time expense and complexity. In order to simply predict the ductile crack initiation life of stiffened steel bridge piers, a total of 33 cases are simulated to carry out the parametric analyses. In the analysis, the effects of the width-to-thickness ratio, slenderness ratio, plate thickness and so on are considered. Both shell analyses and beam analyses about these 33 cases are conducted. The plastic strain and damage index obtained from shell and beam analyses are compared. The modified factor βs is determined based on the predicted results obtained from both shell and beam analyses in order to simulate the strain concentration at the base corner of the steel bridge piers. Finally, three experimental results are employed to verify the validity of the proposed method in this study.