• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.1875-1882
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• 1993

Variable thickness plates are commonly used as structural members in the majority of industrial sectors. Previous fracture mechanics researches on variable thickness plates were limited to mode I loading cases. In practice, however, cracks are usually located inclined to the loading direction. In this respect, combined mode(mode I/II) stress intensity factors $K_{I}$ and $K_{II}$ at the crack tip for a variable thickness plate were obtained by 3-dimensional finite element analysis. Variable thickness plates containing a slant edge crack were chosen. The parameters used in this study were dimensionless crack $length{\lambda}$, slant $angle{\alpha}$, thickness $ratio{\beta}$ and width ratio{\omega}$. Stress intensity factors were calculated by crack opening displacement(COD) and crack sliding displacement(CSD)method proposed by Ingraffea and Manu.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.479-482
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• 2004

The behavior of fatigue delamination in a GLARE(Glass Fiber Reinforced Metal Laminates) under fatigue loading conditions investigated. The behavior of fatigue delamination was examined basing on investigation of the crack and delamination using a SAM (Scanning Acoustic Microscope). The crack and delamination behavior on the relationship among a-N, SAM images and crack length-delamination length were considered. The test results indicated the features of different fatigue delamination and crack growth according to each fiber orientation angle and also obtained to more increase delamination than crack through the relationship between crack length and delamination length in GLARE.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.637-643
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• 2011

The bond-based peridynamic model is able to capture many of the essential characteristics of dynamic brittle fracture observed in experiments: crack branching, crack-path instability, asymmetries of crack paths, successive branching, secondary cracking at right angles from existing crack surfaces, etc. In this paper we investigate the influence of the stress waves on the crack branching angle and the velocity profile. We observe that crack branching in peridynamics evolves as the phenomenology proposed by the experimental evidence: when a crack reaches a critical stage(macroscopically identified by its stress intensity factor) it splits into two or more branches, each propagating with the same speed as the parent crack, but with a much reduced process zone.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2091-2099
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• 2001

Fatigue crack growth behavior of inclined cracked Al 6061-T6 thick aluminum plate(6mm) repaired with the bonded composite patch was studied. A 0°inclined crack bonded reinforced composite patch and 15°, 30°, 45°, 60°inclined crack plates were tested. The effect of patch and inclined angle were studied and compared to each other. Also we investigated to the crack propagation direction and debonding behavior during the fatigue crack growth test. In this paper. a study was con(ducted to get an fatigue life, fatigue crack growth ratio and crack growth direction. Finally, the effectiveness of composite patch on inclined cracked plate was investigated. The results demonstrated thats there was a definite variation in fatigue life and fatigue crack growth behavior depending on the inclined crack angle.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.6
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• pp.993-1000
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• 2002

The objective of this work is to develop the capability to analyze accurately the mixed-mode propagation of a crack in composite structures with elastic orthotropic material stiffness properties and anisotropic material strength characteristics. In order to develop the capability to fully analyze fracture growth and failure in anisotropic structures, we examined the fundamental problem of mixed mode fracture by carrying out the analysis on orthotropic materials with an inclined crack subject to biaxial loading. Our goal here is to include an additional term in the asymptotic expansion of the crack tip stress field and to show that the direction of crack initiation can be significantly affected by that term. We employ the normal stress ratio theory to predict the direction of crack extension. It is shown that the angle of crack extension can be altered by horizontal loads and the use of second order term in the series expansion is important f3r the accurate determination of crack growth direction.

• Journal of the Korean Society of Safety
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• v.20 no.2 s.70
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• pp.38-43
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• 2005

Several nuclear power plants reported that they often found the combination cracks, which consist of longitudinal and circumferential cracks in the tubes. For the burst pressure of a tube with a single longitudinal or circumferential crack several experimental equations have been proposed in published literatures. But for the combination crack appropriate fracture criterion has not been proposed yet. In this study the burst pressures of a tube with a longitudinal crack or a T-type combination crack consisting of longitudinal and circumferential cracks were obtained experimentally and analytically. Fracture parameters such as crack opening angle (COA) were investigated by using elastic plastic analysis. Also the burst pressure far a T-type combination crack located near a tubesheet was considered to develop a length-based criterion. Because most of the axial, circumferential or combination cracks initiate in roll transition zone near the tubesheet.

• Geomechanics and Engineering
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• v.24 no.3
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• pp.215-226
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• 2021

To study the evolution mechanism of cracks in rocks with multiple defects, rock-like samples with multiple defects, such as strip-shaped through-going cracks and cavity groups, are used, and the crack propagation law and changes in AE (acoustic emission) and strain of cavity groups under different inclination angles are studied. According to the test results, an increase in the cavity group inclination angle can facilitate the initial damage degree of the rock and weaken the crack initiation stress; the initial crack initiation direction is approximately 90°, and the extension angle is approximately 75~90° from the strip-shaped through-going cracks; thus, the relationship between crack development and cavity group initiation strengthens. The specific performance is as follows: when the initiation angle is 30°, the cracks between the cavities in the cavity group develop relatively independently along the parallel direction of the external load; when the angle is 75°, the cracks between the cavities in the cavity group can interpenetrate, and slip can occur along the inclination of the cavity group under the action of the shear mechanism rupture. With the increase in the inclination angle of the cavity group, the AE energy fluctuation frequency at the peak stress increases, and the stress drop is obvious. The larger the cavity group inclination angle is, the more obvious the energy accumulation and the more severe the rock damage; when the cavity group angle is 30° or 75°, the peak strain of the local area below the strip-shaped through-going fracture plane is approximately three times that when the cavity group angle is 45° and 60°, indicating that cracks are easily generated in the local area monitored by the strain gauge at this angle, and the further development of the cracks weakens the strength of the rock, thereby increasing the probability of major engineering quality damage. The research results will have important reference value for hazard prevention in underground engineering projects through rock with natural and artificial defects, including tunnels and air-raid shelters.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.2158-2166
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• 1994

In order to understand the package crack emanating from the edge of leadframe after the delamination between leadframe and epoxy molding compound in an electronic packaging of surface mounting type, the M-integral and J-integral in fracture mechanics are obtained. The effects of geometry, material properties and molding process temperature on the package crack are investigated taking into account the temperature dependence of the material properties, which simulates a more realistic condition. If the temperature dependence of the material properties is considered the result of analysis conforms with observations that the crack is kinked at between 50 and 65 degree. However, in case of constant material properties at the room temperature it is found that the J-integral is underestimated and the kink crack angle is different form the observation. The effects of the material properties and molding process temperature on J-integral and crack angle are less significant that the chip size for the cases considered here. It is suggested that the geometric factors such as ship size, leadframe size are to be well designed in order to prevent(or control) the occurrence and propagation of the package crack.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.2
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• pp.112-120
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• 1993

Variable thickness plates are commonly encountered in the majority of mechanical/structural components of industrial applications. And, as a result of the unsymmetry of the structure or the load and the anisoptropy of the materials, the cracks in engineering structures are generally subjected to combined stresses. In spite of considerable practical interest, however, a few fracture mechanics study on combined mode crack in a variable thickness plate have carried out. In this respect, combined mode 1/3 stress intensity factors $K_{1}$ and $K_{3}$ at the crack tip for a variable thickness plate were obtained by 3-dimensional finite element analysis. Variable thickness plates containing a central slant crack were chosen. the parameters used in this study were dimensionless crack length .lambda. crack slant angle .alpha, thickness ratio .betha. and width ratio .omega. Stress intensity factors were calculated by crack opening displacement(COD) and crack tearing displacement(CTD) method proposed by Ingraffea and Manu. The effect of thickness ratio .betha. on $K_{1}$ is relatively great in comparison to $K_{3}$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.2
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• pp.158-164
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• 2004

Steam generator tubes experience widespread degradations such as stress corrosion cracking, wear, tube rupture, denting, fatigue and so on. The resulting damages can cause tube bursting or leak of the primary water which contains radioactivity Therefore the allowable size of the damage is required to be determined on the maintenance purpose. The burst pressure of a tube with a T-type combination crack consisting of longitudinal and circumferential cracks is obtained experimentally and analytically. Fracture parameters such as stress intensity factor and crack opening angle are investigated. Also the burst pressure for a T-type combination crack is compared with that of a single longitudinal crack to develop a length-based criteria.