• Journal of Mechanical Science and Technology
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• v.17 no.2
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• pp.269-279
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• 2003

The anti-plane shear problem of bonded elastic materials containing a crack at an arbitrary angle to the graded interfacial zone is investigated in this paper The interfacial zone is modeled as a nonhomogeneous interlayer of finite thickness with the continuously varying shear modulus between the two dissimilar, homogeneous half-planes. Formulation of the crack problem is based upon the use of the Fourier integral transform method and the coordinate transformations of basic field variables. The resulting Cauchy-type singular integral equation is solved numerically to provide the values of mode 111 stress intensity factors. A comprehensive parametric study is then presented of the influence of crack obliquity on the stress intensity factors for different crack size and locations and for different material combinations, in conjunction with the material nonhomogeneity within the graded interfacial zone.

• Structural Engineering and Mechanics
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• v.18 no.6
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• pp.759-768
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• 2004

The torsion of a penny-shaped crack in a transversely isotropic strip is investigated in this paper. The shear moduli are functionally graded in such a way that the mathematics is tractable. Hankel transform is used to reduce the problem to solving a Fredholm integral equation. The crack tip stress field is obtained by taking the asymptotic behavior of Bessel function into account. The effects of material property parameters and geometry criterion on the stress intensity factor are investigated. Numerical results show that increasing the shear moduli's gradient and/or increasing the shear modulus in a direction perpendicular to the crack surface can suppress crack initiation and growth, and that the stress intensity factor varies little with the increasing of the strip's height.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.7 s.94
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• pp.1710-1718
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• 1993

This paper investigates the problem of a crack approaching two circular holes in an orthotropic infinite plate. The stress intensity factors were obtained by using the modified mapping-collocation method. The present results show excellent agreement with existing solutions for a crack approaching two circular holes in an isotropic infinite plate. In the numerical examples, various types of cross-ply laminated composites were considered. To investigate the effect of orthotropy and geometry(d/R and a/(d-R)) on crack tip singularity, stress intensity factors were considered as functions of the normalized crack length. It is expected that the modified mapping-collocation method can be applied to the analysis of various kinds of cracks existing around the stress-concentration region of composite laminate.

• Journal of Mechanical Science and Technology
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• v.18 no.1
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• pp.114-121
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• 2004

In order to investigate the corrosion fatigue characteristics in the weld of multi-pass welded A 106 Gr B steel pipe, corrosion fatigue tests were performed under the various stress ratios and 3.5 wt% NaCl solution at room temperature. The corrosion fatigue characteristic curves were represented using crack closure concept. The obtained results are as follows : when the load frequency is 1.0 Hz, the crack opening point is transited in the region of $K_{max}$=20∼32 MPaㆍ $m^{1}$2/. In the low stress intensity factor range, the crack opening point is higher than that in air. However, in the high stress intensity factor range, it is lower than that in air. In the cases of 0.1 Hz and 0.01 Hz, the crack opening point gradually decreases to $K_{min}$ with $K_{max}$ increase.rease.

• Journal of the Korean Society of Safety
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• v.15 no.3
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• pp.1-6
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• 2000

In fatigue crack growth test, it is important not only to analyze characteristics of fatigue crack growth but also to determine the threshold stress intensity factor, ${\Delta}K_{th}$. which is the threshold value of fatigue crack growth. Linear regression analysis using fatigue test data near the threshold is suggested to determine the ${\Delta}K_{th}$ in the standard test method but the ${\Delta}K_{th}$ can be affected by a fitting method. And there are some limitations on the linear regression analysis in the case of small number of test data near the threshold. The objective of this study is to investigate differences of the ${\Delta}K_{th}$ due to regression analysis method and to evaluate the relative error range of the ${\Delta}K_{th}$ in same fatigue crack growth test data.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.178-183
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• 1998

This paper examines the crack growth behavior of 7075-T651 and 5052-H32 aluminum alloys for variable load within tensile load range condition. The cantilever beam type specimen with a chevron notch is used in this study. The crack growth and closure are investgated by compliance method. The applied initial stress ratio is R=0.3 and variable load are R=0.65, 0.46. Crack length, stress intensity factor range, ratio of effective stress intensity factor range and crack growth rate etc. are inspected with fracture mechanics estimate.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.5
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• pp.168-172
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• 2000

The stiffened panel is representative of a large portion of aircraft construction and therefore has much practical importance. In this paper, the influence of various shape parameters on the stress intensity factors and the fatigue crack growth in the panels with bonded composite stiffeners are studied experimentally. Results are presented as crack growth rates for various values of crack lengths, stiffness ratios, and stiffening Materials.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.1
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• pp.17-26
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• 2011

CANDU reactor core is composed a few hundreds pressure tubes, which support and locate the nuclear fuels in the reactor. Each pressure tube provides pressure boundary and flow path of primary heat transport system in the core region. In order to guarantee the structural integrity of pressure tube flaws which can be found by in-service inspection, crack growth and fracture initiation assessment have to be performed. Stress intensity factors are important and basic information for structural integrity assessment of planar and laminar flaws (e. g. crack). This paper reviews and confirms the stress intensity factor of axial crack, proposed in CSA N285.8-05, which is an fitness-for-service evaluation code for pressure tubes in CANDU nuclear reactors. The stress intensity factors in CSA N285.8-05 were compared with stress intensity factors calculated by three methods (finite element results, API 579-1/ASME FFS-1 2007 Fitness-For-Service and ASME Boiler and Pressure Vessel Code Section XI). The effects of Poisson's ratio and anisotropic elastic modulus on stress intensity factors were also discussed.

• Journal of the Korean Society of Safety
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• v.9 no.1
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• pp.3-8
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• 1994

This paper has described the analysis of the Stress Intensity Factor behaviour of a short crack Initiated from notch tip. The model for finite element analysis is a double edge notched specimen. The parameters used in this study are crack length and notch root curvature radius.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.8
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• pp.137-145
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• 1997

A two-dimensional program for the analysis of bimaterial inclusion has been developed using the bound- ary element method. In order to study the effects of circular inclusion on the stress field of the crack tip, numerical analysis was performed for the straight crack of finite length around the symmetric circular inclusion whose modulus of elasticity was different from that of the matrix material. In the case of inclusion whose stiffness was smaller than that of the matrix material, the stress intensity factor was found to increase as the crack enamated. The stress intensity factor was uninfluenced from the radial change in inclusion and remained constant for the stiffness equivalent to the matrix materials, where as it decreased for the inclusion with larger stiffness. For the vareation in the distance of the inclusion, a small increase in the stress intensity factor was observed for the case with small or equal stiffness compared with the matrix materials. The inclusion with larger stiffness showed a gradual decrease in the strss intensity factor as the crack emanated.