• Title/Summary/Keyword: fracture load

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Studies on the effect of thermal shock on crack resistance of 20MnMoNi55 steel using compact tension specimens

  • Thamaraiselvi, K.;Vishnuvardhan, S.
    • Nuclear Engineering and Technology
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    • v.53 no.9
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    • pp.3112-3121
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    • 2021
  • One of the major factors affecting the life span of a Reactor Pressure Vessel (RPV) is the Pressurised Thermal Shock (PTS). PTS is a thermo-mechanical load on the RPV wall due to steep temperature gradients and structural load created by internal pressure of the fluid within the RPV. Safe operating life of a nuclear power plant is ensured by carrying out fracture analysis of the RPV against thermal shock. Carrying out fracture tests on RPV/large scale components is not always feasible. Hence, studies on laboratory level specimens are necessary to validate and supplement the prototype results. This paper aims to study the fracture behaviour of standard Compact Tension [C(T)] specimens, made of RPV steel 20MnMoNi55, subjected to thermal shock through experimental and numerical investigations. Fracture tests have been carried out on the C(T) specimens subjected to thermal transient load and tensile load to quantify the effect of thermal shock. Crack resistance curves are obtained from the fracture tests as per ASTM E1820 and compared with those obtained numerically using XFEM and a good agreement was found. A quantitative study on the crack tip plastic zone, computed using cohesive segment approach, from the numerical analyses justified the experimental crack initiation toughness.

A Study on Deformation and Strength of High-Strength Polymer Composites Using Automobiles (자동차용 고강도 폴리머 복합재료의 변형과 강도에 관한 연구)

  • Im, Jae-Gyu;Sin, Jae-Hun;Park, Han-Ju;Shoji, T.;Takeda, H.
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.7
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    • pp.1082-1088
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    • 2001
  • Nowadays study on recycling disused plastics for automobiles was lively progressed. Rubber and talcum powder was added to retrieve degradation of physical properties caused by recycling disused polypropylene. The effect of the temperature, the fatigue load and the loading speed on DEN(double edged notch) specimen which was made by the pp-rubber composites during fracture was studied by. DEN specimen was made on PP-rubber composites through the injection molding. With increasing temperature the fracture strength was linearly decreased and the fracture energy was increased by $0^{\circ}C$ and after that decreased. In the same temperature the fracture strength during increasing the notch radius was hardly increased. The fracture behaviour at low and high loading speed was different entirely. At high loading speed plastic region was small and fracture behaviour was seen to brittle fracture tendency. With increasing fatigue load fracture energy was first rapidly decreased and subsequently steady when radius of notch tip was 2mm, but Maximum load during fracture scarcely varied. The deformation mechanism of polypropylene-rubber composites during fracture was studied by SEM fractography. A strong plastic deformation of the matrix ahead of the notch/crack occurred. The deformation seem to be enhanced by a thermal blunting of the notch/crack.

Measurement of load history of Kyoung-Bu line by using the diesel locomotive (디젤기관차를 이용한 경부선의 하중이력 측정)

  • 함영삼;서정원;오택열
    • Proceedings of the KSR Conference
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    • 2000.05a
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    • pp.652-659
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    • 2000
  • The machine structure or parts has been arrive at a fracture, depend on crack by repeated load. Machine designer is estimate of fatigue strength in early stages the design for prevent fatigue fracture, then necessary its load history. This research study is using diesel locomotive in measurement of load history for fatigue design of rolling stock. The relation between velocity and amplitude of load history was found. We confirmed that the increase of velocity make to increase the magnitude of amplitude.

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A Study of Fiber Content Effect on the Fracture Behavior of Glass/Polypropylene Composites (유리섬유/폴리프로필렌 복합재에서 섬유 함유비가 파괴특성에 미치는 영향에 대한 연구)

  • 이경엽;신동혁;이중희
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.5
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    • pp.173-178
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    • 2001
  • This study investigates the effect of fiber content on the fracture behavior of thermoplastic composites (glass fiber/polypropylene). The fiber contents used were 20%, 30%, and 40% by weight. Fracture tests were performed using compact tension (CT) specimens made of composite sheets of three fiber contents (20%, 30%, 40%). The results showed that compliance, fracture load, and fracture toughness were affected by the fiber content. The compliance decreased with fiber content while the fracture load increased as the fiber content increased. The fracture toughness also increased as fiber content increased. Specifically, the fracture toughness increased 14% as the fiber content increased from 20% to 40%.

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The Effect of residual stress for fracture behavior in the laser weldment (레이저용접부의 파괴에 미치는 잔류응력의 영향)

  • Jo, Seong-Gyu;Yang, Yeong-Su
    • Proceedings of the Korean Society of Laser Processing Conference
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    • 2006.06a
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    • pp.3-8
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    • 2006
  • The integrity of laser welded structures is decided with fracture strength and fatigue strength. This study presents fracture behavior considering residual stress in the laser welding. Experiments are conducted and analyses are performed to explore the influence of residual stress on fracture behavior of bead-on laser welded compact specimen. Fracture experiments are performed using ASTM 1820. The performed analyses included thermo-elasto-plastic analyses for residual stress and subsequent J-integral calculation. A modified J integral is calculated in the presence of residual stresses. The J-integral is path-independent for combination of residual stress field and stress due to mechanical loading. The results indicates that the tensile residual stress near crack front bring the low fracture load while the compressive residual stress bring the high fracture load compared to no residual stress specimen. These results quantitatively understand the influence of residual stress on fracture behavior.

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The Effect of residual stress on fracture behavior in the laser weldment (레이저용접부의 파괴에 미치는 잔류응력의 영향)

  • Cho, Sung-Kyu;Yang, Young-Soo;Noh, Young-Jin
    • Laser Solutions
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    • v.11 no.2
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    • pp.1-7
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    • 2008
  • The integrity of laser welded structures is decided in fracture strength and fatigue strength. This study made an effort to understand the fracture behavior considering residual stress. Experiments are conducted and analyses are performed to explore the influence of residual stress on fracture behavior of bead-on laser welded compact specimen. Fracture experiments are performed using ASTM 1820. The performed analyses included thermo-elasto-plastic analyses for residual stress and subsequent J-integral calculation. A modified J integral is calculated in the presence of residual stresses. The J-integral is path-independent for combination of residual stress field and stress due to mechanical loading. The results indicates that the tensile residual stress near crack front bring the low fracture load while the compressive residual stress bring the high fracture load compared to no residual stress specimen. These results quantitatively understand the influence of residual stress on fracture behavior.

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Estimation of the Fracture Resistance Curve for the Nuclear Piping Using the Standard Compact Tension Specimen (표준 CT시험편을 이용한 실배관 파괴저항 곡선 예측)

  • Park, Hong-Sun;Heo, Yong;Koo, Jae-Mean;Seok, Chang-Sung;Park, Jae-Sil;Cho, Sung-Keun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.9
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    • pp.930-937
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    • 2009
  • The estimation method of the fracture resistance curve for the pipe specimen was proposed using the load ratio method for the standard specimen. For this, the calculation method of the load - CMOD curve for the pipe specimen with the common format equation(CFE) was proposed by using data of the CT specimen. The proposed method agreed well with experimental data. The J-integral value and the crack extension were calculated from the estimated load - CMOD data. The fracture resistance curve was estimated from the calculated J-integral and the crack extension. From these results, it have been seen that the proposed method is reliable to estimate the J-R curve of the pipe specimen.

A Study on the Measurement of the Crack Length for the Real Scale Pipe Specimen (실배관 시험편의 균열 길이 측정에 관한 연구)

  • Park, Jae-Sil;Seok, Chang-Sung
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.397-402
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    • 2003
  • Fracture resistance curves for concerned materials are required in order to perform elastic-plastic fracture mechanical analyses. Fracture resistance curve is built with J-integral values and crack extension values. The objective of this paper is to apply the load ratio method to the measurement of the crack length for the real scale pipe specimen. For these, the fracture test using the real scale pipe specimen and finite element analyses were performed. A 4-point bending jig was manufactured for the pipe test and the direct current potential drop method and the load ratio method was used to measure the crack extension and the length for the real scale pipe test. Finite element analyses about the compliance of the pipe specimen were executed for applying the load ratio method according to the crack length.

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Optimization of Kiln Process Parameters of Low-Temperature Sintering Lightweight Aggregate by Response Surface Analysis (반응표면분석법에 따른 저온소성 경량골재의 킬른공정변수 최적화)

  • Lee, Han-Baek;Seo, Chee-Ho
    • Journal of the Korean Ceramic Society
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    • v.47 no.5
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    • pp.365-372
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    • 2010
  • This paper was to evaluate the influence of kiln process parameter(kiln angle, kiln rotating speed) of lightweight aggregate using waste glass and bottom ash with industrial by-products on thermal conductivity, density, water absorption, fracture load and porosity by response surface analysis. In the results of surface plot and contour plot, it has verified that kiln residence time of lightweight aggregate increase as kiln angle and rotating speed decreases. For this reason, pore size and quantity tend to increase by active reaction of forming agent. It seems to be that increase in pore size and quantity have caused decreasing density, fracture load and thermal conductivity, and increasing water absorption. In conclusion, optimization of kiln process parameter on thermal conductivity, density, water absorption, fracture load and porosity by response surface analysis are kiln angle 2.4646%, kiln rotating speed 40.7089 rpm.

Evaluation of Fracture Behavior and Formation of Microcrack of Alumina Ceramics by Acoustic Emission (AE에 의한 알루미나 세라믹스의 Microcrack 생성과 파괴거동의 평가)

  • 장병국;우상국
    • Journal of the Korean Ceramic Society
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    • v.35 no.6
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    • pp.551-558
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    • 1998
  • Detection of microcrack in {{{{ {Al }_{2 } {O }_{3 } }} ceramics were studided by AE(acoustic emission) technique with 4-point bending test in order to evaluate the fracture process and formation of microcrack. Fully-dense alu-mina ceramics having a different grain size were fabricated by varing the hot-pressing temperature. The grain size of alumina increased with increasing the hot-pressing temperature whereas the bending strength decreasd. The microcracks were observed by SEM and TEM. The generation of AE event increased with increasing the applied load and many AE event was generated at maximum applied load. Alumina with smaller grain size shows the generation of many AE event resulting in an increase of microcrack formation. An intergranular fracture is predominantly observed in fine-grained alumina whereas intragranular fracture occurs predominantly in coarse-grained alumina,. Analysis of micorstructure and AE prove that primary mi-crocracks occur within grain-boundaries of alumina. The larger microcracking were formed by the growth and/or coalesence of primary microcracks. Then the materials become to fracuture by main crack gen-eration at the maximum applied load.

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