• Title/Summary/Keyword: Fracture toughness

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A Study on the Nondestructive Evaluation of Material Properties (비파괴적인 재료물성치 평가에 관한 연구)

  • Kim Hyung-Ick;Kim Jeong-Pyo;Seok Chang-Sung
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.3
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    • pp.130-136
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    • 2005
  • The nondestructive evaluation system consisted of a ball indentation tester and a ultrasonic tester was developed to evaluate material properties. The relations between the parameters from test results using the system and the results of tensile and fracture toughness tests were investigated. The fracture toughness and tensile properties could be determined using the system. Some metallic materials were experimented to predict the fracture toughness and tensile properties and verify the relations between them. The predicted fracture toughness and tensile properties show a good agreement with the results obtained by conventional tests. It is found that the material properties and the material degradation can be evaluated using the nondestructive evaluation system.

Effect of Volume Fraction of Chromium Carbide on Fracture Toughness of the Iron/Chromium Hardfacing Alloy (철/크롬 오버레이합금의 파괴인성에 미치는 크롬탄화물 양의 영향)

    • Journal of Welding and Joining
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    • v.16 no.2
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    • pp.64-72
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    • 1998
  • This study aims a investigating the effect of volume fraction of chromium carbide phase(VFC) of hardfaced iron/chromium alloys on fracture toughness. The alloys were deposited twice on a mild steel plate using self-shielding flux cored arc welding process. In order to examine VFC effect, different VFC (0.28∼0.62) were employed by changing the Cr and C content, while the ratio of Cr/C was fixed in the range of 5.7∼6.6. Fracture toughness was constant as increasing VFC because fracture surface was developed in the eutectic phase which was growing parallel with introduced sharp notch in the hypoeutectic alloys, but fracture toughness did not decreased in spite of increasing volume fraction of coarse primary chromium carbide phase which was easily craced at the low stress because the growth direction of chromium carbide phase were more irregular as increasing VFC in the hypereutectic alloys.

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An Evaluation Method of Fracture Toughness on Interface Crack in Friction Welded Dissimilar Materials (이종 마찰용접재의 계면균열에 대한 파괴인성의 평가방법)

  • Chung, Nam-Yong;Park, Cheol-Hee
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.4
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    • pp.171-177
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    • 2007
  • In this paper, an evaluation method of fracture toughness on interface cracks was investigated in friction welded dissimilar materials with interfacial edge cracks. To establish a reasonable strength evaluation method and fracture criterion, it is necessary to analyze stress intensity factor under the load and residual stress condition on friction welded interface between dissimilar materials. The friction welded specimens with an edged crack were prepared for analysis of stress intensity by using the boundary element method (BEM) and the fracture toughness. A quantitative fracture criterion for friction welded STS 304/SM 45C with interface crack is suggested by using stress intensity factor, F and the results of fracture toughness experiment.

Effect of Composition on the Hardness and Toughness in PZT-PYW Ceramics (PZT-PYW 세라믹스의 조성변화가 경도 및 인성에 미치는 영향)

  • 류소연;임대순;윤석진;김현재
    • Journal of the Korean Ceramic Society
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    • v.31 no.3
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    • pp.305-311
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    • 1994
  • In this paper, a change of fracture toughness and hardness in PZT-PYW ceramics system before and after poling treatment was measured to investigate the effect of composition on the mechanical properties in PZT-PYW ceramics. The hardness of the PZT-PYW ceramics increased with increasing mole fraction of PYW. The fracture toughness achieved maximum values for x=0.03. Both of the hardness and the fracture toughness also increased with poling treatment. The variation of both hardness and fracture toughness with increasing PYW mole fracture was explained by the change in microstructures such as grain size and second phase. The difference in hardness and fracture toughness in the electrically poled and unpoled specimens was also explained on the bases of internal stress.

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Statistical Evaluation of Fracture Characteristics of RPV Steels in the Ductile-Brittle Transition Temperature Region

  • Kang, Sung-Sik;Chi, Se-Hwan;Hong, Jun-Hwa
    • Nuclear Engineering and Technology
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    • v.30 no.4
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    • pp.364-376
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    • 1998
  • The statistical analysis method was applied to the evaluation of fracture toughness in the ductile-brittle transition temperature region. Because cleavage fracture in steel is of a statistical nature, fracture toughness data or values show a similar statistical trend. Using the three-parameter Weibull distribution, a fracture toughness vs. temperature curve (K-curve) was directly generated from a set of fracture toughness data at a selected temperature. Charpy V-notch impact energy was also used to obtain the K-curve by a $K_{IC}$ -CVN (Charpy V-notch energy) correlation. Furthermore, this method was applied to evaluate the neutron irradiation embrittlement of reactor pressure vessel (RPV) steel. Most of the fracture toughness data were within the 95% confidence limits. The prediction of a transition temperature shift by statistical analysis was compared with that from the experimental data.

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Dynamic Crack Initiation of 17-4PH Casting Steel for Various Notch Radius (다양한 노치 반경을 갖는 17-4PH강의 동적균열개시 특성)

  • 박성욱;김덕회;김재훈;문순일
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.160-163
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    • 2003
  • In this study, intrinsic dynamic fracture toughness of 17-4PH casting steel is evaluated from the apparent dynamic fracture toughness of notched specimen. Notch radius of notched specimen is manufactured from 0.1mm to 4mm. The results shows that dynamic fracture toughness decreases with decreasing of notch root radius above critical notch roof radius. The true dynamic fracture toughness can be predicted from test results of apparent dynamic fracture toughness measured by using notched specimen.

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Influence of MWCNTs on Fracture Toughness of MWCNTs/Nickel-Pitch Fiber/Epoxy Composites

  • Yim, Yoon-Ji;Park, Soo-Jin
    • Composites Research
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    • v.28 no.6
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    • pp.361-365
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    • 2015
  • The influence of MWCNTs on fracture toughness properties of MWCNTs/Nickel-Pitch Fibers/epoxy composites (MWCNTs/Ni-PFs/epoxy) was investigated according to MWCNTs content. Nickel-Pitch-based carbon fibers (Ni-PFs) were prepared by electroless nickel-plating. The surface properties of Ni-PFs were determined by scanning electron microscopy (SEM) and X-ray photoelectron spectrometry (XPS). The fracture toughness of MWCNTs/Ni-PFs/epoxy was assessed by critical stress intensity factor ($K_{IC}$) and critical strain energy release rate ($G_{IC}$). From the results, it was found that the fracture toughness properties of MWCNTs/Ni-PFs/epoxy were enhanced with increasing MWCNTs content, whereas the value decreased above 5 wt.%. MWCNTs content. This was probably considered that the MWCNTs entangled with each other in epoxy due to an excess of MWCNTs.

A Study on High Temperature Fracture Toughness Characterisitics of Spring Steel by Compressive Residual Stress (압축잔류응력이 스프링강(SUP-9)의 고온파괴인성에 미치는 영향에 관한 연구)

  • Jung, Jae-Wook;Park, Won-Jo;Lee, Kwang-Young;Huh, Sun-Chul
    • Proceedings of the KSME Conference
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    • pp.314-319
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    • 2004
  • High temperature fracture toughness characteristics of shot peened spring steel(SUP-9), which is used for automobile suspension system and railroad, was investigated in this paper. Fracture tougness test for room temperature, $100^{\circ}C$ , and $200^{\circ}C$ were evaluated by material test system(MTS). The experimental results show that the fracture toughness was improved by peened and unpeened. The fracture toughness for high temperature were also improved by peened and unpeened.

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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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The Size Effect in Measuring the Fracture Toughness of Rock using Chevron Bend Specimen (암석의 파괴인성 측정에서 나타나는 CB 시험편의 치수효과에 관하여)

  • 김재동;백승규
    • Tunnel and Underground Space
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    • v.2 no.2
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    • pp.251-264
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    • 1992
  • In this study, the size effect in measuring the fracture toughness of rock was investigated using the ISRM Suggested Method for Fracture toughness using Chevron Bend Specimens. Total 58 specimens were prepared with 4 different diameters, 29, 42, 54, 68mm and center cut-chevron notch. In addition to this, to evaluated the effect of anisotropy of Jecheon granite, which is the sample for this study, core drilling direction was adjusted perpendicular(short transverse) and parallel(arrester) to the rift plane in the sample and the measured fracture toughness for each direction were compared. Important results obtained from this study are as follows. Level ll test condition is more adequate than l, because of low data scattering and precision and corrected fracture toughness of Jechoen granite measured and 2.2MPa{{{{ SQRT { m} }}}} for arrester direction with minimum initial crack length 0.7cm. From the relationship between core diameter and initial crack length presented in the ISRM testing method, the specimen diameter should be bigger than 47mm. The fracture toughnesses measured for arrester and short transverse directon show 10% difference. This is to the anisotropy of Jecheon granite possessing rift plane.

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