• Title/Summary/Keyword: Crack direction

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An Analysis of Flat-Crack in Homogeneous Anisotropic Solids Considering Non-Singular Term (비특이항을 고려한 균질이방성체내 수평균열의 해석)

  • Im, Won-Gyun;Choe, Seung-Ryong;An, Hyeon-Su
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.1 s.173
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    • pp.69-78
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    • 2000
  • The one-parameter singular expression for stresses and displacements near a crack tip has been widely thought to be sufficiently accurate over a reasonable re ion for any geometry and loading conditions. In many cases, however subsequent terms of the series expansion are quantitatively significant, and so we now consider the evaluation of such terms and their effect on the predicted crack growth direction. For this purpose the problem of a cracked orthotropic plate subjected to a biaxial load is analysed. It is assumed that the material is ideal homogeneous anisotropic. BY considering the effect of the load applied parallel to the plane of the crack, the distribution of stresses and displacements at the crack tip is reanalyzed. In order to determine values for the angle of initial crack extension we employ the normal stress ratio criterion.

Effects of $K_{II}$ on fatigue crack propagation behavior of wedzone in generally rolled steel for marine structure (박용 구조물용 일반압연강 용접부의 피로균열 전파거동에 미치는 $K_{II}$의 영향)

  • 한문식;김상철
    • Journal of Welding and Joining
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    • v.6 no.3
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    • pp.43-55
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    • 1988
  • An experimental study was carried out to identify the fatigue fractue behavior of weld zone in generally rolled steel for marine structure. The bending an shear loads were applied simultaneously on the specimens to simulate real load condition for marine structure. The effect of the stress intensity factor under mode I with II loading condition on the initiation and the propagation of a crack were investigated, with particular emphaiss on mode II. When the $K_{II}$ stress intensiy factor in mode II was applied under mode I load condition, the growth behavior of a crack seems to be affected mainly by the anisotropic characteristic of materials. Especially, when the crack was located in and near the weld zone and parallel to th weld line, the propagation behaviour was turned out to be quite different from that of the base metal along the direction transverse to the weld line. In general, the propagation veiocity of the cracks in and near the weld zone was found to be slower that the velocity in base metal.

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Finite Element Analysis of Subsurface Crack Propagation in Half-space Due to Sliding Contact (유한요소법을 이용한 미끄럼 접촉시의 반무한체 내의 수평균열 전파해석)

  • 이상윤;김석삼
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1999.06a
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    • pp.297-302
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    • 1999
  • Finite element analysis is peformed about the crack propagation in half-space due to sliding contact. The analysis is based on linear elastic fracture mechanics and stress intensity factor concept. The crack location is fixed and the friction coefficient between asperity and half-space is varied to analyze the effect of surface friction on stress Intensity factor for horizontal crack. The crack propagation direction is predicted based on the maximum range of shear and tensile stress intensity factor.

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A Fracture Mechanics Analysis of Bonded Repaired Skin/Stiffener Structures with Inclined Central Crack (경사균열을 갖는 Skin/Stiffener 구조물의 보수에 의한 균열의 파괴역학적 거동)

  • Chung, Ki-Hyun;Yang, Won-Ho;Kim, Cheol;Heo, Sung-Pil;Ko, Myung-Hoon
    • Proceedings of the KSME Conference
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    • 2001.06a
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    • pp.292-297
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    • 2001
  • Composite patch repair of cracked aircraft structures has been accepted as one of improving fatigue life and attaining better structural integrity. Analysis for the stress intensity factor at the skin/stiffener structure with inclined central crack repaired by composite stiffened panels are developed. A numerical investigation was conducted to characterize the fracture behavior and crack growth behavior. In order to investigate the crack growth direction, maximum tangential stress(MTS) criteria is used. The main objective of this research is the validation of the inclined crack patching design. In this paper, the reduction of stress intensity factors at the crack-tip and prediction of crack growth direction are determined to evaluate the effects of various non-dimensional design parameter including; composite patch thickness and stiffener distance. The research on cracked structure subjected to mixed mode loading is accomplished and it is evident that more work using different approaches is necessary.

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이중하중을 받는 S45C의 피로거동에 관한 연구

  • 윤두연;이원석;이현우
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1992.04a
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    • pp.268-273
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    • 1992
  • Thin walled tubular specimens of 0.45% structural carbon steel were used in the bizxial tests. Biaxial fatigue tosts were conducted on strain control including fully reversed tension-compression and in phase tension torsion loadings. The predictions of the biaxial fatigue life were based upon the uniaxial low cycle fatigue test results. Fatigue lives were ranged from 10$\^$2/to 10$\^$5/cycles. Four multiaxial strain based theories have been developed to correlate biaxial fatigue experimdntal results. These theories showed good correlatins except for maximum shear strain theory. In uniaxial tests, crack behavior was observed that crack initiated in the maximum shear strain direction and propagated in the direction perpendicular to principal stross. But, in biaxial tests, both crack initiation and growth occured on the maximum shear strain direction only.

Influence of Electric Poling an Fracture Toughness of Ferroelectric-Ferroelastic PZT Ceramics

  • Zuokai Ke;Sunggi Baik
    • The Korean Journal of Ceramics
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    • v.1 no.4
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    • pp.197-203
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    • 1995
  • Nearly fully dense PZT samples both with tetragonal and with morphotropic phase boundary compositions were prepared by the conventional powder processing and sintering. A micro-indentation technique was used to evaluate the dependence of fracture toughness on remanent polarization, crack length and the direction of crack propagation. The result shows that the toughness increases with the remanent polarization along the poling direction and decreases in the transverse direction. The dependence of toughness on the remanent polarization is neither symmetric nor linear but rather shown to be saturated quickly with the increase in remanent polariztion. R-curve behaviors are observed in both poled and unpoled samples. Sequential SEM and XRD studies on annealed, poled, ground, fractured and etched samples show that domain switching is evident as a viable toughening mechanism but might depend upon the rate of crack propagation. Grain bridging is also observed as one of the active toughening mechanisms.

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A Study on the Dynamic Stress Intensity Factor of Orthotropic Materials(II) A Study on the Stress Field, Displacement Field and Energy Release Rate in the Dynamic Mode III under Constant Crack Propagation Velocity (직교 이방성체의 동적 응력확대계수에 관한 연구 (II) 등속균열전파 속도하에서 동적모드 III 상태의 응력장, 변위장, 에너지해방률에 관한 연구)

  • 이광호;황재석;최선호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.2
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    • pp.331-341
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    • 1993
  • The propagating crack problems under dynamic antiplane mode in orthotropic material is studied in this paper. To analyze the dynamic fracture problems by theoretical method or experimental method in orthotropic material, it is important to know the dynamic stress intensity factor in the vicinity of crack tip. Therefore the dynamic stress field and dynamic displacement field with dynamic stress intensity factor of orthotropic material in mode III were derived. When the crack propagation speed approachs to zero, the dynamic stress components and dynamic displacement components derived in this paper are identical to the those of static state. In addition, the relationships between dynamic stress intensity factor and dynamic energy release rate are determined by using the concept of crack closure energy with the dynamic stresses and dynamic displacements derived in this paper. Finally, the characteristics of crack propagation are studied with the properties of orthotropic material and crack speed. The variation of angle .alpha. between fiber direction and crack propagating direction and crack propagation speed fairly effect on stress component and displacement component in crack tip. The influence of crack propagation speed on the speed on the stress and displacement is greater in the case of .alpha.=90.deg. than in the case of .alpha.=0.deg. and the faster the crack propagation speed, the greater the stress value and displacement value.

A Study on the Fatigue Crack Growth of Cracks in Mechanical Joints (기계적 체결부 균열의 피로균열성장에 관한 연구)

  • 허성필;양원호;정기현
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.1
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    • pp.187-194
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    • 2002
  • It has been reported that cracks in mechanical joints is generally under mixed-mode and there is critical inclined angle at which mode I stress intensity factor becomes maximum. The crack propagates in arbitrary direction and thus the prediction of crack growth path is needed to provide against crack propagation or examine safety. In order to evaluate the fatigue life of cracks in mechanical joints, horizontal crack normal to the applied load and located on minimum cross section is major concern but critical inclined crack must also be considered. In this paper mixed-mode fatigue crack growth test is performed far horizontal crack and critical inclined crack in mechanical joints. Fatigue crack growth path is predicted by maximum tangential stress criterion using stress intensity factor obtained from weight function method, and fatigue crack growth rates of horizontal and inclined crack are compared.

Characteristics for a Mode III Crack Propagating along Interface between Isotropic and Functionally Gradient Material with Linear Property Gradation along X Direction (등방성과 X방향 선형함수구배 재료의 접합계면을 따라 전파하는 모드 III 균열의 특성)

  • Lee Kwang Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.10
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    • pp.1500-1508
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    • 2004
  • Stress and displacement fields for a crack propagating along interface between isotropic material and functionally gradient one with linear property gradation along X direction are developed. The stress and displacement fields are obtained from the complex function of steady plane motion for isotropic and functionally gradient material (FGM). The stresses and displacement in isotropic material of bimaterial are not influenced by nonhomogeneity, however, the fields in FCM are influenced by nonhomogeneity in the terms of higher order, n$\geq$3. When the nonhomogeneous parameter in FGM is zero, or in area close to crack tip, the fields are identical to those of isotropic-isotropic bimaterial. Using these stress components, the effects of nonhomogeneity on stresses are discussed.

Development of Crack Examination Algorithm Using the Linearly Integrated Hall Sensor Array (선형 홀 센서 배열을 사용한 결함 검사 알고리즘 개발)

  • Kim, Jae-Jun;Kim, Byoung-Soo;Lee, Jin-Yi;Lee, Soon-Geul
    • Journal of the Korean Society for Precision Engineering
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    • v.27 no.11
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    • pp.30-36
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    • 2010
  • Previous researches show that linearly integrated Hall sensor arrays (LIHaS) can detect cracks in the steel structure fast and effectively This paper proposes an algorithm that estimates the size and shape of cracks for the developed LIHaS. In most nondestructive testing (NDT), just crack existence and location are obtained by processing 1-dimensional data from the sensor that scans the object with relative speed in single direction. The proposed method is composed with two steps. The first step is constructing 2-dimensionally mapped data space by combining the converted position data from the time-based scan data with the position information of sensor arrays those are placed in the vertical direction to the scan direction. The second step is applying designed Laplacian filter and smoothing filter to estimate the size and shape of cracks. The experimental results of express train wheels show that the proposed algorithm is not only more reliable and accurate to detecting cracks but also effective to estimate the size and shape of cracks.