• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.6 s.177
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• pp.1557-1564
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• 2000

When the half infinite crack in the orthotropic material strip with a large anisotropic ratio(E11>>E22) propagates with constant velocity, dynamic stress component $\sigma$y occurre d along the $\chi$ axis is derived by using the Fourier transformation and Wiener-Hopf technique, and the dynamic stress intensity factor is derived. The dynamic stress intensity factor depends on a crack velocity, mechanical properties and specimen hight. The normalized dynamic stress intensity factors approach the maximum values when normalized time(=Cs/a) is about 2. They have the constant values when the normalized time is greater than or equal to about 2, and decrease with increasing a/h(h: specimen hight, a: crack length) and the normalized crack propagation velocity( = c/Cs, Cs: shear wave velocity, c: crack propagation velocity).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.5
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• pp.513-523
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• 2016

The stress concentration factors and stress intensity factors for a simple beam and a cantilever are analyzed by using finite element method and phtoelasticity. Using the analyzed results, the estimated graphs on stress concentration factors and stress intensity factors are obtained. To analyze stress concentration factors of notch, the dimensionless notch length H(height of specimen)/h=1.1~2 and dimensionless gap space r(radius at the notch tip)/h=0.1~0.5 are used. where h=H-c and c is the notch length. As the notch gap length increases and the gap decreases, the stress concentration factors increase. Stress concentration factors of a simple beam are greater than those of a cantilever beam. However, actually, the maximum stress values under a load, a notch length and a gap occur more greatly in the cantilever beam than in the simple beam. To analyze stress intensity factors, the normalized crack length a(crack length)/H=0.2~0.5 is used. As the length of the crack increases, the normalized stress intensity factors increase. The stress intensity factors under a constant load and a crack length occur more greatly in the cantilever beam than in the simple beam.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.569-578
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• 1998

The mode I and II stress intensity factors have been calculated theoretically for the cracked plate reinforced with a plate by symmetric spot welding under remote mixed mode loading. This is the extension of authors' previous work for the reinforced cracked plate under remote normal stress. Regardless of loading types, the reinforcement effect gets better as one joining spot is closer to the crack tip and the others are closer to the crack surface, and optimum number of the joining spots can be existed. For the present model, the remote loading parallel to crack surface produces the mode I stress intensity factor.

• Journal of the Korean Society for Nondestructive Testing
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• v.8 no.1
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• pp.22-29
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• 1988

The optical method of reflected and transmitted caustics has been utilized in mechanics investigations. This relatively new experimental technique has been successfully applied on various fracture analysis such as static and dynamic c rack propagation studies, some elasticity problems and contact stress, etc, In this study, the stress intensity factors in thin polycarbonate specimens, a kind of optically anisotropic material, under Mode I loading condition are estimated by the method of caustics. The values of stress intensity factors obtained from theoretical caustics shape are compared by the experiment. It is confirmed that the two stress intensity factors agree well with Srawley's solution.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.648-653
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• 2003

In order to predict stress intensity limit of high-temperature creep structures, creep work-time equation, defined as $W_ct^P=B$, was used, and the results of the equation were compared with isochronous stress-strain curve (ISSC) ones of ASME BPV NH Code. For this purpose, the creep strain tests with. time variations for commercial type 316 stainless steel were conducted with different stresses; 160 MPa, 150 MPa, 145 MPa, 140 MPa and 135 MPa at $593^{\circ}C$. The results of log $W_c$ and log t plots showed a good linear relation up to $10^5$ hr. The constants p, B and stress intensity limit values showed comparatively good agreement to those of ASME NH ISSC. It is believed that the relation can be simply obtained with only several short-term 1% strain data without ISSC which can be obtained by long-term creep data.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.560-566
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• 2000

Many researchers have dealt with the problems of fracture mechanics. Generally, these researches are concerned with crack in isotropic material without other micro defects. Actual structure, however, may contain micro defects as well as crack in manufacture processing or operation. If it contains mi defects near a crack, some different characteristics will be appear in fracture behaviors of the crack. This study examines the effect of the micro defect on stress intensity factor of center slant crack rectangular plate subjected to uniform uniaxial tensile stress. In this study, boundary element method(BEM) is used for analysis in stress intensity factor(SIF).

• Journal of the Korean Society for Precision Engineering
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• v.17 no.5
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• pp.180-185
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• 2000

An interface V-notched crack problem can be formulated as a eigenvalue problem. there are the eigenvalues which give stress singularities at the V-notched crack tip. The RWCIM is a method of calculating the eigenvector coefficients associated with eigenvalues for a V-notched crack problem. Obtaining the stress intensity factors for an interface crack in dissimilar materials is examined by the RWCIM. The results of stress intensity factors for an interface crack are compared with those of the displacement extrapolation method by the BEM

• International Journal of Korean Welding Society
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• v.1 no.2
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• pp.18-22
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• 2001

The stress intensity factor has been calculated theoretically for the cracked plate subjected to remote normal stress and reinforced with a plate by symmetric seam welding. The singular integral equation was derived based on displacement compatibility condition between the cracked plate and the reinforcement plate, and solved by means of Erdogan and Gupta's method. The results from the derived equation for stress intensity factor were compared with FEM solutions and seems to be reasonable. The reinforcement effect gets better as welding line is closer to the crack and the stiffness ratio of the cracked plate and the reinforcement plate becomes larger.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2344-2352
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• 2000

Mechanical joints such as bolted or riveted joints are widely used in mechanical components. The reliable determination of the stress intensity factors for cracks in bolted joints is needed to evaluate the safety and fatigue life of them. The weight function method is an efficient technique to calculate the stress intensity factors for various loading conditions because only the stress analysis of an uncracked model is required. In this paper the mixed-mode stress intensity factors for cracks in bolted joints are obtained by weight function method, in which the coefficients of weight function are determined by finite element analyses for reference loadings. Critical inclined angle that mode I stress intensity factor becomes maximum is determined and the effects of crack length and the magnitude of clearance on critical inclined angle are investigated.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.111-116
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• 2000

A semi-infinite interfacial crack propagated with constant velocity in two bonded anisotropic strip under out-of-plane clamped displacements is analyzed. The asymptotic stress and displacement fields near the crack tip are obtained, where the results get more general expressions applicable not only to isotropic/orthotropic materials but also to the extent of the anisotropic material having one plane of elastic symmetry for the interfacial crack. The dynamic stress intensity factor is obtained as a closed form, which is decreased as the velocity of crack propagation increases. The critical velocity where the stress intensity factor comes to zero is obtained, which agrees with the lower value between the critical values of parallel crack merged in the material 1 and 2 adjacent to the interface. The dynamic energy release rate is also obtained as a form related to the stress intensity factor.