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Ductile Fracture Behaviour of SA 533B Pressure Vessel Steel Under Mixed Mode (I/II) Loading (혼합 모드(I/II) 하중에 의한 SA533B 압력용기강의 연성파괴 특성에 관한 연구)

  • O, Dong-Jun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.11
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    • pp.1829-1834
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    • 2001
  • The aim of this study is to investigate the ductile fracture behavior under mixed mode (I/II) loading using SA533B pressure vessel steel. Anti-symmetric 4-point (AS4P) bonding tests were performed to obtain the J-R curves under two different mixed mode (I/II) loadings. In addition, the fractographic examination of fracture surfaces was carried out to compare with those of pure Mode I and Mode II. In conclusions, the J-R curves under Mixed Mode (I/II) loading were located between those of Mode I and Mode II loadings. When the mixture ratio of mixed mode (I/II) loading was high, the J-R currie of mixed mode (I/II) loading approached that of pure mode I loading after some amount of crack propagation. In contrast with the above fact, if the mixture ratio was low, the J-R curve looked after that of pure mode II loading. The fractographic evidences such as the shape of dimples under different loading conditions supported these conclusions.

Ductile Fracture Behavior of AS4P Under Mixed Mode (I/II) Loading

  • Oh, Dong-Joon
    • Journal of Mechanical Science and Technology
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    • v.16 no.4
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    • pp.476-484
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    • 2002
  • The aim of this study is to investigate the ductile fracture behavior under mixed mode (I/II) loading using SA533B pressure vessel steel. Anti-symmetric 4-point (AS4P) bending tests were performed to obtain the J-R curves under two different mixed mode (I/II) loadings. In addition, finite element analysis using Rousselier Ductile Damage Theory was carried out to predict the J-R curves under mixed mode (I/II) loadings. In conclusions, the J-R curves under. Mixed Mode (I/II) loading were located between those of Mode I and Mode II loading. When the mixity of mixed mode (I/II) loading was high, the J-R curve of mixed mode (I/II) loading approached that of pure mode I loading after some amount of crack propagation. In contrast with the above fact, if the mixity was low, the J-R curve took after that of pure mode II loading. Finally, it was found that the predicted J-R curves made a good agreement with the test data through the tuning procedures of $\beta$ values at the different mixed mode (I/II) loading.

Success Factor of m-commerce; A case of DoCoMo′s i-Mode Service (기술언어가 m-commerce의 성공에 미치는 영향에 관한 소고 - i-mode 서비스를 중심으로 -)

  • 김광희
    • Proceedings of the Korea Inteligent Information System Society Conference
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    • pp.305-314
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    • 2001
  • 본 논문해서는 m-커머스의 대표적인 성공 사례로 꼽히고 있는 NTT DoCOMo의 i-mode 서비스에 초점을 맞추어 성공요인과 그러한 성공을 이끌어 내는데 결정적인 역할을 담당한 웹 페이지 기술언어에 대해 살펴보았다. 분석 결과에 근거하면, i-mode 서비스의 대대적인 성공은 끊임없이 Positive Feedback의 계기를 만들어 냄으로써 가능하게 되었는데, 그것은 다름 아닌 C-HTML이라는 웹페이지 기술언어의 채용이 많은 역할을 하고 있다.

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Crack Growth Behavior by Fatigue Load under Mixed Mode(I+II) (혼합모드(I+II)에서 피로 하중에 의한 균열진전 거동)

  • Gong, B.C.;Choi, S.D.
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.21 no.2
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    • pp.276-282
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    • 2012
  • This study looked for Mode status of each for fatigue crack growth behavior about the repeat load of mode I and the static load of mode II. The experiment was performed in the state of the repetition frequency of the sine wave 10Hz, the stress ratio 0.1, maximum load 300kg.f, a static load 0, 100, 200, 300kg.f, As the experimental results, in mode of static load, while the load value increases, the crack growth rate is slower as the energy of a crack mixing grows. Mode I and the power mode II get an influence each other in the direction of crack propagation path, but as they eventually get closer to the breaking point of the crack growth, it is dominated by the mode I.

Effects of Fine Contents on the Fracture Characteristics of Frozen Sand (세립분 함유량이 동결 사질토의 파괴특성에 미치는 영향)

  • Hwang, Bumsik;Cho, Wanjei
    • Journal of the Korean Geotechnical Society
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    • v.36 no.3
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    • pp.25-36
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    • 2020
  • In this research, three-point bending tests were performed using a rectangular frozen specimen with various fine contents and notch offset distance from the center of the specimen to investigate the fracture characteristic of the frozen sand. Based on the test results, mode I fracture toughness was calculated, and mixed-mode (mode I + II) fracture characteristics were investigated using the fracture energy which was calculated until the maximum point of the load-displacement curve. As the fine contents increase, the peak load and mode I fracture toughness increase until 10% fine contents. Furthermore, as the notch offset distance increases, the fracture energy required for crack start also increases due to the increase in mode II load at the crack tip.

An Experimental Study on the Evaluaiton of Elastic-Plastic Fracture Toughness under Mixed Mode I-II-III Loading Using the Optical PSD (PSD를 이용한 혼합모드 하중하에서 탄소성 파괴인성평가에 관한 실험적인 연구)

  • Kim, Hei-Song;Lee, Choon-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.4
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    • pp.1263-1274
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    • 1996
  • In this paper, as elastic-plastic fracture toughness test under mixed mode loading was proposed using a single edge-cracked specimen subjected to bending moment(M), shearing force(F), and twisting moment(T). The J-integral of a crack in the specimen is expressed in the form J=$J_I$+ $J_II$$J_III$, where $J_I$, $J_II$ and $J_III$ are the components of mode I, mode II and mode III deformation, respectively. $J_I$, $J_II$ and $J_III$ can be estimated from M-$\theta$ ($\theta$;crack opening angle), F-U(U; crack shear displacement) and T-$\alpha$ ($\alpha$;crack twisting angle). In order to obtain the the M<-TEX>$\theta$, F-U and T-$\alpha$ diagram inreal time, a new deformaiton gage for mixed mode loading was proposed using the optical position sensing device(PSD). The elastic-plastic fracture toughness test was carried out with an aluminum alloy. The loading apparatus was designed and manufactured for this experiment. For the loading condition of the crack initatio in the mixed mode, the MMT -3(mode I+ mode II+ mode III) has the lowest values out of the all specimens. This implies that MMT-3 is possible of the crackinitation at lower load, if the specimen acts on together with the torque under the same loading condition. An elastic-plastic fracture toughness test using the PSD brings a successful experimentation in measuring the crack deformation(mode I+ mode II+ mode III).

Numerical studies of information about elastic parameter sets in non-linear elastic wavefield inversion schemes (비선형 탄성파 파동장 역산 방법에서 탄성파 변수 세트에 관한 정보의 수치적 연구)

  • Sakai, Akio
    • Geophysics and Geophysical Exploration
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    • v.10 no.1
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    • pp.1-18
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    • 2007
  • Non-linear elastic wavefield inversion is a powerful method for estimating elastic parameters for physical constraints that determine subsurface rock and properties. Here, I introduce six elastic-wave velocity models by reconstructing elastic-wave velocity variations from real data and a 2D elastic-wave velocity model. Reflection seismic data information is often decoupled into short and long wavelength components. The local search method has difficulty in estimating the longer wavelength velocity if the starting model is far from the true model, and source frequencies are then changed from lower to higher bands (as in the 'frequency-cascade scheme') to estimate model elastic parameters. Elastic parameters are inverted at each inversion step ('simultaneous mode') with a starting model of linear P- and S-wave velocity trends with depth. Elastic parameters are also derived by inversion in three other modes - using a P- and S-wave velocity basis $('V_P\;V_S\;mode')$; P-impedance and Poisson's ratio basis $('I_P\;Poisson\;mode')$; and P- and S-impedance $('I_P\;I_S\;mode')$. Density values are updated at each elastic inversion step under three assumptions in each mode. By evaluating the accuracy of the inversion for each parameter set for elastic models, it can be concluded that there is no specific difference between the inversion results for the $V_P\;V_S$ mode and the $I_P$ Poisson mode. The same conclusion is expected for the $I_P\;I_S$ mode, too. This gives us a sound basis for full wavelength elastic wavefield inversion.

Crack tip plastic zone under Mode I, Mode II and mixed mode (I+II) conditions

  • Ayatollahi, M.R.;Sedighiani, Karo
    • Structural Engineering and Mechanics
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    • v.36 no.5
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    • pp.575-598
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    • 2010
  • The shape and size of the plastic zone around the crack tip are analyzed under pure mode I, pure mode II and mixed mode (I+II) loading for small scale yielding and for both plane stress and plane strain conditions. A new analytical formulation is presented to determine the radius of the plastic zone in a non-dimensional form. In particular, the effect of T-stress on the plastic zone around the crack tip is studied. The results of this investigation indicate that the stress field with a T-stress always yields a larger plastic zone than the field without a T-stress. It is found that under predominantly mode I loading, the effect of a negative T-stress on the size of the plastic zone is more dramatic than a positive T-stress. However, when mode II portion of loading is dominating the effect of both positive and negative T-stresses on the size of the plastic zone is almost equal. For validating the analytical results, several finite element analyses were performed. It is shown that the results obtained by the proposed analytical formulation are in very good agreements with those obtained from the finite element analyses.

Metamaterial CRLH Structure-based Balun for Common-Mode Current Indicator

  • Kahng, Sungtek;Lee, Jinil;Kim, Koon-Tae;Kim, Hyeong-Seok
    • Journal of Electrical Engineering and Technology
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    • v.9 no.1
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    • pp.301-306
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    • 2014
  • We proposed a new PCB-type 'common-mode current($I_c$) and differential-mode current($I_d$) detector' working for fast detection of $I_c$ and $I_d$ from the differential-mode signaling, with miniaturization effect and possibility of cheaper fabrication. In order to realize this device, we suggest a branch-line-coupler balun having a composite right- and left-handed(CRLH) one-layer microstrip phase-shifting line as compact as roughly ${\lambda}_g/14$. The presented balun obviously is different from the conventional bent-&-folded delay lines or slits on the ground for coupling the lines on the top and bottom dielectrics. As we connect the suggested balun output ports of the differential-mode signal lines via the through-port named U and coupled-port named L, $I_c$ and $I_d$ will appear at port ${\Delta}$ and port ${\Sigma}$ of the present device, in order. The validity of the design scheme is verified by the circuit-and numerical electromagnetic analyses, and the dispersion curve proving the metamaterial characteristics of the geometry. Besides, the examples of the $I_c$ and $I_d$ indicator are observed as the even and odd modes in differential-mode signal feeding. Also, the proposed device is shown to be very compact, compared with the conventional structure.

Assessment for Propagation Behavior and Fracture Surface of Mixed-mode Fatigue Crack by Fracture Surface-Roughness Induced Crack Closure (파면거칠기 유도 균열닫힘에 의한 혼합모드 피로균열의 전파거동 및 파면에 대한 평가)

  • Seo, Ki-Jeong;Lee, Jeong-Moo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.4
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    • pp.432-440
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    • 2007
  • In this study, we have investigated the closure behavior of fatigue cracks in SAPH440 steel plates under a mixed-mode I+II loading. A crack image capturing system as a direct measuring method was used to measure the closure levels at a crack tip. The crack closure levels in the fluctuation and stable sections were increased with the increase of the mode mixture ratio. The mode mixture ratio independent fatigue crack propagation rates equation was calculated by considering mixed-mode crack closure levels. The equation was examined according to the application method of crack opening ratio. The fracture surface analysis by C-scan method was also performed in order to investigate the closure mechanism and propagation mode of crack under the mixed-mode I+II loading. The crack closure under the mixed mode I+II is confirmed as a surface roughness closure by the quantitative analysis of fracture surface using the proposed surface roughness parameter.