• Title/Summary/Keyword: Effective Toughness

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Analysis of Failure Criterion for Combustion Pipe with Notch using Effective Distance (유효거리를 이용한 연소기관 노치부의 파손기준 해석)

  • Kim, Duck-Hoi;Kim, Jae-Hoon;Moon, Soon-Il
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1-6
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    • 2004
  • In this study, the intrinsic static/dynamic fracture toughness of Al 7175=T74 is evaluated from the apparent static/ dynamic toughness of notched specimen, The critical average stress fracture model is suggested to establish the relationship to predict the intrinsic fracture toughness from the apparent fracture toughness of a notched specimen. The critical average stress fracture model is established using the relation between the notch root radius and the effective distance calculated by finite element analysis. Also, effective distance is applied to estimate the failure criterion for the combustion pipe with notch. It is conclude that the true fracture toughness can be estimated from test results of apparent fracture toughness measured by using a notched specimen. Also, the effective In this study, the intrinsic static/dynamic fracture toughness of Al 7175=T74 is evaluated from the apparent static/ dynamic toughness of notched specimen, The critical average stress fracture model is suggested to establish the relationship to predict the intrinsic fracture toughness from the apparent fracture toughness of a notched specimen. The critical average stress fracture model is established using the relation between the notch root radius and the effective distance calculated by finite element analysis. Also, effective distance is applied to estimate the failure criterion for the combustion pipe with notch. It is conclude that the true fracture toughness can be estimated from test results of apparent fracture toughness measured by using a notched specimen. Also, the effective distance can be used to evaluate the failure criterion of structure with notch.

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Effects of Cu and B on Effective Grain Size and Low-Temperature Toughness of Thermo-Mechanically Processed High-Strength Bainitic Steels (TMCP로 제조된 고강도 베이나이트강의 유효결정립도와 저온인성에 미치는 Cu와 B의 영향)

  • Lee, Seung-Yong;Hwang, Byoungchul
    • Korean Journal of Materials Research
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    • v.24 no.10
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    • pp.520-525
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    • 2014
  • Effects of Cu and B on effective grain size and low-temperature toughness of thermo-mechanically processed high-strength bainitic steels were investigated in this study. The microstructure of the steel specimens was analyzed using optical, scanning, and transmission electron microscopy; their effective grain size was also characterized by electron back-scattered diffraction. To evaluate the strength and low-temperature toughness, tensile and Charpy impact tests were carried out. The specimens were composed of various low-temperature transformation products such as granular bainite (GB), degenerated upper bainite (DUB), lower bainite (LB), and lath marteniste (LM), dependent on the addition of Cu and B. The addition of Cu slightly increased the yield and tensile strength, but substantially deteriorated the low-temperature toughness because of the higher volume fraction of DUB with a large effective grain size. The specimen containing both Cu and B had the highest strength, but showed worse low-temperature toughness of higher ductile-brittle transition temperature (DBTT) and lower absorbed energy because it mostly consisted of LB and LM. In the B-added specimen, on the other hand, it was possible to obtain the best combination of high strength and good low-temperature toughness by decreasing the overall effective grain size via the appropriate formation of different low-temperature transformation products containing GB, DUB, and LB/LM.

Evaluation of Effective Toughness of Steel Fiber Reinforced Concrete (강섬유 보강 콘크리트의 유효인성 평가)

  • 구봉근;정경섭
    • Magazine of the Korea Concrete Institute
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    • v.4 no.2
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    • pp.103-110
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    • 1992
  • 본 연구는 인성지수에 의하여 섬유보강 콘크리트의 인성을 평가하는 기존의 여러 가지 방법을 검토하는, 하중-처짐곡선에서 초기균열시까지의 여러 가지 다른 곱으로 나타내어지는 방법의 불합리성을 지적하였다. 이를 위하여 본 연구에서는 유효인성이라고 부르는 새로운 방법을 강섬유 보강콘크리트의 인성을 평가하는데 제안하였다. 이는 초기균열을 가진 3점 휨강도 시험에 의한 하중-처짐곡선에서 지간의 1/150까지의 면적을 ligament면적으로 나눈값으로 나타낸다. 이 방법을 사용하여 강섬유 보강 고강도 콘크리트 인성특성을 검토한 결과 기존의 방법보다 더 효과적으로 인성을 평가할 수 있었다.

A Comparative Study on Flexural Toughness of Steel Fiber Reinforced Concrete (강섬유 보강 콘크리트의 휨파괴 인성지수의 결정에 관한 비교 연구)

  • 구봉근;정경섭;김태봉;박종인
    • Proceedings of the Korea Concrete Institute Conference
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    • 1991.04a
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    • pp.69-74
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    • 1991
  • This paper reviewed various methods of evaluating the toughness of fiber reinforced concrete materials by means of toughness indices and discussed the use of various multiples of first-crack deflection or first-crack secant compliance to define toughness indices. And a new method what is called effective toughness used to evaluate the toughness of steel fiber reinforced concrete. The proposed method determinded from the area below the load-deflection curve until deflection at the loading point becoms 1/150 of the span devided by the ligament area.

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Evaluation of Critical Notch radius using Notch/Crack Critical Average Stress Fracture Model (노치/균열 임계평균응력 파손모델을 이용한 임계노치반경 평가)

  • 김재훈;김덕회;김기수;안병욱
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.1358-1361
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    • 2003
  • In this study, intrinsic static/dynamic fracture toughness of Al 7175-T74 are evaluated from the apparent static/dynamic toughness of notched specimen. The notch/crack critical average stress fracture model is suggested to establish the relationship to predict the intrinsic fracture toughness from the apparent fracture toughness of a notched specimen. The notch/crack critical average stress fracture model is established using the relation between the notch root radius and the effective distance calculated by finite element analysis. It is conclude that the true fracture toughness can be estimated from test results of apparent fracture toughness measured by using a notched specimen. Also, critical notch root radius can be predicted by notch/crack critical average stress fracture model.

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Notch Radius Effect for Static Fracture Toughness of Al 7175 Alloys (Al 7175 합금의 정적 파괴인성에 미치는 노치반경 영향)

  • 김재훈;김덕회;박성욱;문순일
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2002.04a
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    • pp.84-87
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    • 2002
  • In this study, intrinsic fracture toughness of Al 7175-T74 is evaluated from the apparent toughness of notched specimen. Modified average stress model is used to establish the relationship to predict the intrinsic fracture toughness from the apparent fracture toughness of a notched-cracked specimen. The modified average stress model is established the relation between notch radius and effective distance calculated by FEM analysis. The results show that fracture toughness decreases with decreasing of notch root radius. The true fracture toughness can be predicted from test results of apparent fracture toughness measured by using notched specimen.

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Evaluation of Fracture Toughness and Microstructure on FCA Weldment According to Heat Input (입열량에 따른 FCAW용접부 파괴인성에 미치는 미세조직의 영향)

  • Shin, Yong-Taek;Kang, Sung-Won;Kim, Myung-Hyun
    • Journal of Welding and Joining
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    • v.26 no.3
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    • pp.51-60
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    • 2008
  • This paper is to evaluate fracture characteristics of API 2W Gr.50 TMCP steel weldment typically applied for offshore structures, with the focus on the influence of heat input arising from flux cored arc welding. Based on the results and insights developed from this study, it is found that the toughness for both CTOD and impact exhibits a tendency to decrease as the weld heat input increases. The reheated zone of weldmetal exhibit lower hardness than solidified zone and microstructure that are liable to affect the toughness are acicular ferrite and martensite-austenite constituents (M-A). In particular, M-A is a more effective micro-phase for CTOD toughness than impact toughness.

Numerical analysis on the welding residual stress and fracture toughness of the heavy thick steel welded joints by welding processes

  • Bang, HanSur;Bang, HeeSeon
    • Journal of Welding and Joining
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    • v.33 no.2
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    • pp.32-39
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    • 2015
  • This study examined the welding residual stress and fracture toughness of 78mm thick steel electro gas welding (EGW) and flux cored arc welding (FCAW) welded joints by numerical analyses of the thermal elasto-plastic behavior and fracture toughness(KIC). The residual stress, fracture toughness characteristics and production mechanism on the welded joints were clarified. Moreover, the effects of the welding process (EGW and FCAW) on the welding residual stresses and fracture toughness of welded joints were evaluated. The results showed that the new welding process (EGW) appears to be an effective substitute for the existing welding process (FCAW) in a thick steel plate with high strength.

A Study on Local Distribution of Fracture Toughness for Welded Joints of Steel Structure (구조강(構造鋼) 용접부(鎔接部)의 국부인성분포(局部靭性分布)에 관한 연구(研究))

  • Chang, Dong Il;Young, Hwan Sun;Kim, Dong Hee
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.4 no.3
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    • pp.19-25
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    • 1984
  • In the welded structure, the most dengerous section is welded parts and almost fractures of welded structure occur from welded parts. Accordingly, in other to prevents of fracture, it is important seeking the fracture behavior of welded parts. In this study as basic investigation of fracture behavior of welded parts, it is investigated that local distribution of fracture toughness and effect of multipass electrode welding, also effect of release of residual stress were investigated, as the subjected. material, the used steel having fatigue history and unused steel were selected. As the result of this study, it is dear that the base metal of unused steel and heat affected zone and weld metal are different each other in fracture toughness, and it seems clear that the weld metal may will become source of fracture because of it having the most low fracture toughness. Especially, in the case of crack occur in the used steel, it will be the most brittle section in the structure because of it having low fracture toughness then weld metal. It affirmation that, if welded parts has not flaw, the multi pass electrode welding effective to improve of fracture toughness, also release of residual stress is none effective to improve of fracture toughness in this study.

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A Study on the Compliance of a Compact Tension Test Specimen (소형인장시험편의 컴플라이언스에 관한 고찰)

  • Jeong, Gi-Hyeon;Seok, Chang-Seong;Yang, Won-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.12
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    • pp.3010-3017
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    • 2000
  • For integrity evaluation of cracked or damaged structures, fracture toughness test results in ASTM are widely used. The fracture toughness values of the structures are used as an effective design criterion in nuclear plants and aircraft structures. Sometimes the difference of P-$\delta$ curve trend during the unloading /reloading cycle in the fracture toughness test using partial unloading compliance was observed. The phenomenon as a possible source of error in determining fracture toughness may be caused by the residual stress during unloading work-hardening and bucking of a specimen. Therefore, we evaluate the effect of bucking and compressive residual stress during the K-R and J-R testing using a finite element method.