• Title, Summary, Keyword: Fracture behaviour

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Eccentrically compressive behaviour of RC square short columns reinforced with a new composite method

  • Zhang, Fan;Lu, Yiyan;Li, Shan;Zhang, Wenlong
    • Steel and Composite Structures
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    • v.27 no.1
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    • pp.95-108
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    • 2018
  • A new composite reinforced method, namely self-compacting concrete filled circular CFRP-steel jacketing, was proposed in this paper. Experimental tests on eight RC square short columns reinforced with the new composite reinforced method and four RC square short columns reinforced with CFS jackets were conducted to investigate their eccentrically compressive behaviour. Nine reinforced columns were subjected to eccentrically compressive loading, while three reinforced columns were subjected to axial compressive loading as reference. The parameters investigated herein were the eccentricity of the compressive loading and the layer of CFRP. Subsequently, the failure mode, ultimate load, deformation and strain of these reinforced columns were discussed. Their failure modes included the excessive bending deformation, serious buckling of steel jackets, crush of concrete and fracture of CFRP. Moreover, these reinforced columns exhibited a ductile failure globally. Both the eccentricity of the compressive loading and the layer of CFRP had a significant effect on the eccentrically compressive behaviour of reinforced columns. Finally, formulae for the evaluation of the ultimate load of reinforced columns were proposed. The theoretical formulae based on the ultimate equilibrium theory provided an effective, acceptable and safe method for designers to calculate the ultimate load of reinforced columns under eccentrically compressive loading.

Ductile Fracture Behaviour of SPS Specimen Under Pure Mode II Loading (순수 모드 II하중 하에서의 SPS 시험편의 연성파괴 특성에 관한 연구)

  • O, Dong-Jun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.2
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    • pp.289-295
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    • 2001
  • The aim of this study is to investigate the ductile fracture behaviour under pure Mode II loading using A533B pressure vessel steel. Single punch shear(SPS) test was performed to obtain the J-R curve under pure Mode II loading which was compared with that of the Model I loading. Simulation using Rousellier Ductile Damage Theory(RDDT) was carried out with 4-node quadrilateral element(L(sub)c=0.25mm). For the crack advance, the failed element removal technique was adopted with a $\beta$ criterion. Through the $\beta$ value tuning-up procedures, $\beta$(sub)crit(sup)II was determined as 1.5 in contrast with $\beta$(sub)crit(sup)I=5.5. In conclusion, it was found that the J-R curve under Mode II loading was located at lower part than that under Mode I loading obtained from the previous study and that the $\beta$ values strongly depended on the loading type. In addition, the predicted result using RDDT showed a good agreement with the SPS experimental one under pure Mode II loading.

Development of Analytical Simulation Model for Fatigue Crack Propagation : Crack Closure Behavior Modeling (균열개폐구 거동을 고려한 피로균열전파 해석 모델의 개발 : 균열 개폐구 거동의 모형화)

  • C.W. Kim;I.S. Nho;H.H. Van;B.C. Shin
    • Journal of the Society of Naval Architects of Korea
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    • v.38 no.3
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    • pp.74-83
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    • 2001
  • After the concept of fracture mechanics was applied to fatigue crack propagation by Paris. Paris' law is widely used to predict fatigue crack growth behavior. Since Elber proposed the effective stress intensity factor(SIF) and showed a good agreement with experimental results using the proposed SIF, emphasis in crack propagation studies has been placed on measuring the effective stress range ratio. This paper proposes a numerical model to simulate the crack closure and propagation behaviour under various loading spectrum. The validity of the proposed model is checked by comparing with the Toyosada numerical solutions on the crack propagation behaviour. Important insights developed are summarized.

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An Experimental Study on Shear Behaviour of Reinforced High Strength Concrete Beams (고강도 철근콘크리트 보의 전단거동에 관한 실험적 연구)

  • 곽계환;고갑수;곽경헌
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.38 no.3
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    • pp.58-69
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    • 1996
  • In recent years, the research and development about the new material proceeds rapidly and actively. In building industry, high strength concrete is of interest as a new material. Since the building structure becomes bigger, higher and more specialized, the demand of material and member with high strength expands greatly. Therefore in this experiment, cement complex with high strength was made using the condensed silica fume, a basic experiment was performed on strength property, and optimum-mixture-state was determined for manufacturing a high-strength concrete. Shear behaviour and fracture property of concrete beams with high strength were evaluated. On the whole, in spite of many researches, it is one of the difficult problems that shear fracture of concrete beams has not yet been clearly understood theoretically, and now the shear-design-standard forms in many countries are a formula based on experiment. In this study, the variable of shear behavior experiment was shear-reinforcement-ratio. By analyzing test results and comparing with computation value by ACI code, the basic data was offered on shear design of reinforced concrete beams with high strength. The effect of epoxy repair was also investigated for the beams with cracks due to flexural and shear loading.

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Study on Surface Crack Propagation Behaviour of Mild Steel Weldment in Synthetic Sea Water (인공해수중에서 연강 용접부의 표면구열 성장거동)

  • 이종기;정세희
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.2
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    • pp.492-501
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    • 1990
  • It was known that the fracture incidences of offshore structure were mostly originated from the surface defects. Especially, in the case of the welded structures, since the welded region has some defects and incomplete beads which are apt to behave like the surface cracks, it has been necessary to evaluate the environmental effects on crack growth at HAZ for the design crack growth behaviour at multi-pall HAZ for SWS41 steel under free corrosion and cathodic protection(-0.9V vs Ag/Agcl) conditions. The results are summarized as follows ; (1) Crack growth rate of the as weld in air was faster than that of the parent and PWHT specimens over all .DELTA.K rang. (2) In free corrosion test, surface crack growth rate of the as welded was decreased in comparison with that of the parents. (3) In fatigue test under cathodic protection, cathodic electric potential(-0.9V vs Ag/Agcl) for the SWS41 steel parent was effective, while for the as welded ineffective. (4) There was a tendency that the exponent(m) of the Paris' equation was decreased in order of microhardness magnititude in air and under cathodic protection conditions and vise versa in free corrosion. (5) Fracture surface has dimples and ductile striations in air test, but transgranular cracks and brittle striations under cathodic protection test.

The Effect of The Second Phase Morphology on the Micro And Macro Fracture Behaviour of Dual Phase Steel (鋼 의 微視 및 巨視的 破壞擧動 에 미치는 第二相形態 의 영향)

  • 김정규;송삼홍;이장현
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.6 no.3
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    • pp.239-246
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    • 1982
  • The effect of the second phase morphology on the fracture ductility of dual phase steel was studied by means of tensile tests carried out room temperature. In this case the second phase morphology is characterized by two kinds; one is the MEF microstructure in which martensite encapsulated islands of ferrite, the other is the FEM microstructure in which ferrite encapsulated islands of martensite. The fracture ductility is improved by variation of the second phase morphology, but is essentially uneffected in the range of high strength ratio (4.7). Also the variation of ductility is well understood according to the difficulty of cleavage crack formation of the ferrite grain and to the brittleness of the martensitic structure.

Effect of the grain size of temperature dependence on the creep behavior of SUS 316 (SUS 316 강의 온도의존성 결정입경이 크리이프 거동에 미치는 영향)

  • Oh, Sae-Wook;Kang, Oug
    • Journal of Welding and Joining
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    • v.1 no.2
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    • pp.61-68
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    • 1983
  • Austenitic stainless steel has been investigated widely for creep strength of heat resistant material and effects of grain sizes due to various solution treatment time under constant temperature. It was studied that effects of grain sizes subject to solution treatment temperature 1100.deg. C, 1125.deg. C, 1175.deg. C, 1250.deg C, and 1300.deg. C respectively on the creep strength, fracture behaviour and fractography of SUS 316 stainless steel. The experimental results obtained were as follows. 1. The optimum grain size for the maximum creep strength did not vary with creep testing temperatures and stress levels. 2. Among various grain sizes due to different solution treatment temperature, the optimum grain size for the creep strength was found 0.044mm. Also the size showed the minimum initial strain regardless creep temperature. 3. Garofalo's equation of creep rupture life was applied well to SUS 316 stainless steel. 4. The fractography of optimum size was ductile intergranular fracture of dimple type and showed along with the increase of grain size intergranular fracture of w type.

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A Study on Fatigue Fracture Behaviour of Surface Crack in Finite Plates and Fillet Weldment (유한평판 및 필렛 용접부에 있어서 표면균열의 피로 파괴거동에 관한 연구)

  • 한문식
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.4
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    • pp.65-73
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    • 2004
  • Fatigue crack growth from surface defects is one of the most important subjects for the evaluation and the assurance of safety in pressure vessels, piping systems, LPG/LNG fuel tank and other various structures. This paper attempts to analysis some practical or general problems such as the estimation of crack growth life to penetrate the plate thickness, based on fatigue crack growth a single surface flaw and the interaction of multiple flaws. An experiment on the coalescence of multiple undercuts was carried out under cyclic tension condition as a attempt to the analysis of multiple crack problems. It is noted that the fracture strength is characterized by the analogy to that in a single crack growth.

A Study on the Effect of Fiber Orientation on the Interlaminar Fracture Toughness (층간파괴인성치에 대한 섬유방향의 영향에 관한 연구)

  • Lee, Jung-Kyu;Um, Yoon-Sung;Kim, Hyung-Jin;Koh, Sung-Wi
    • Journal of Ocean Engineering and Technology
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    • v.9 no.2
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    • pp.89-97
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    • 1995
  • The investigate the effect of fiber orientation on the interlaminar fracture toughness of carbon fiber reinforced plastics three prepregs which are domestic products are used in this paper. Those are used for the unidirectional composites, but only one is used for the cross-ply laminate composites which is molded $[0/90]_{6s},\;[0/45]_{6s},\;and\;[0/45/90]_{4s}$. The specimens used for the mode I and mode II Tests are DCB and ENF samples are examined by scanning electron microscope(SEM). The value of $G_{IC}$ is almost same when modified three calculating methods are applied. The highest value of $G_{IC}$at crack initiation is obtained at the $[0/90]_{6s}$ interlaminar and the lowest one is at the $[0/45/90]_{4s}$ interlaminar. The highest value of $G_{IIC}$ at crack initiation, however, is obtained at the $[0/90]_{6s}$ interlaminar and the lowest one is at the $[0/45]_{6s}$. The photographs of SEM show a difference behaviour between mode I and mode II fracture surface.

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Evaluation of Elastic-Plastic Fracture Toughness of Aged AISI 316 Steel Using DC-electric Potential Method (직류전위차법을 이용한 AISI 316강 시효재의 탄소성 파괴인성 평가)

  • Lim, Jae-Kyoo;Chang, Jin-Sang;Lino, Y.
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.3
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    • pp.519-527
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    • 1997
  • AISI 316 steel has been used extensively for heater and boiler tube of the structural plants such as power, chemical and petroleum plants under severe operating conditions. Usually, material degradation due to microcrack or precipitation of carbides and segregation of impurity elements, is occured by damage accumulated for long-term service at high temperature in this material. In this study, the effect of aging time on fracture toughness was investigated to evaluate the measurement of material degradation. The elastic-plastic fracture toughness behaviour of AISI 316 steel pipe aged at $550^{\circ}C$for 1h-10000h (the aged material) was characterized using the single specimen J-R curve technique and eletric potential drop method at normal loading rate(load-line displacement speed of 0.2mm/min) in room temperature and air environment. The fracture toughness data from above experiments is compared with the $J_{in}$ obtained from predicted values of crack initiation point using potential drop method.