• Proceedings of the KWS Conference
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• 2000.04a
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• pp.260-263
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• 2000

In this study, constant amplitude fatigue tests on load-carrying fillet welded specimen carried out, and fatigue strengths were evaluated. Also, an attempt is made to develop a new analytical model with more accuracy to predict the fatigue crack propagation life of fillet welded cruciform joints of SWS 490B steels containing lack of penetration defects. from the result of this study, fatigue crack growth characteristics of load-carrying fillet welded cruciform joints, containing lack of penetration defacts are found to be affected by the weld geometry and the number of weld pass.

• Structural Engineering and Mechanics
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• v.20 no.3
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• pp.335-346
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• 2005

The T-stress of cracks in elastic sheets is solved by using the fractal finite element method (FFEM). The FFEM, which had been developed to determine the stress intensity factors of cracks, is re-applied to evaluate the T-stress which is one of the important fracture parameters. The FFEM combines an exterior finite element model with a localized inner model near the crack tip. The mesh geometry of the latter is self-similar in radial layers around the tip. The higher order Williams series is used to condense the large numbers of nodal displacements at the inner model near the crack tip to a small set of unknown coefficients. Numerical examples revealed that the present approach is simple and accurate for calculating the T-stresses and the stress intensity factors. Some errors of the T-stress solutions shown in the previous literature are identified and the new solutions for the T-stress calculations are presented.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.301-304
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• 2003

Nowadays, hydration heat analysis using FEM is common in thermal crack control of concrete structure. Many kinds of general FEM programs for hydration heat analysis are used in practice. But there are some problems in this using. In this study hydration heat analysis of wall according to placement length are performed. In this results we could get two conclusions. First, general structures like wall having general geometry and construction condition have similar behavior. So it is not necessary to analysis thermal crack in every case. Second, the results of 2D analysis is possible to be applied instead of those of 3D analysis because the results of 2D analysis is similar to 3D analysis in long wall having about 15~18m or over length at 3m height.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.9
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• pp.967-974
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• 2007

A general form solution is considered for a piezoelectric material containing impermeable cracks subjected to a combined mechanical and in-plane electrical loading. The analysis is based upon the Hilbert problem formulation. Using this solution, typically for a central crack in transverse isotropic piezoelectric material, a closed form solution is obtained, where one concentrated mechanical and electrical load is subjected to the crack surface. This problem could be used as a Green's function to generate the solutions of other problems with the same geometry but of different loading conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.4
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• pp.662-670
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• 2001

We evaluate the effectiveness and validity of J(sub)e, which comprehensively describes the effects of specimen geometry and loading type, in predicting the fatigue life of auto seat belt anchor panel. We first simplify the heat affected zone model to reduce the number of finite elements. We then establish finite element models reflecting the actual overload behavior of 3 types of seat belt anchor specimens. Using finite element models elaborately established, we obtain the effective crack driving parameter J(sub)e composed of its ductility-dependent modal components. It is confirmed that the J(sub)e concept successfully predicts the fatigue life of multi-spot welded panel structures represented by auto seat belt anchors here.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.304-308
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• 2000

In this work, an equation of J-integral for a penny-shaped crack at the end of the cord embedded in rubber matrix is proposed. The dimensional analysis is applied to derived to the equation of J-integral. We assume that the energy Parameter J is separated into the deformation and the geometry function, and which is proved using by separation parameter.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.4
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• pp.133-141
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• 1996

The mode of fatigue failure is depended on the characteristics of the fatigue crack initiated and propagated from the weld toe and the weld root in the load-carrying fillet welded joints. The characteristics of fatigue crack are deeply affected by the geometry of fillet and the stress range. The purpose of this study is to investigate critical weld size and stress range in order to occur toe failure under pulsating tension loading in the load-carrying fillet welded cruciform joints.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.11 s.242
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• pp.1488-1493
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• 2005

In this study, fatigue tests to obtain S-N curves and FE analyses to obtain structural stress concentration factors were conducted for the two types of cruciform fillet welded joints, that is, load-carrying and non load-carrying types. Then we changed the obtained S-N curve of load carrying joint to that based on hot spot stress. As a result, the S-N curve of load carrying joint based on hot-spot stress was almost exactly coincided with that of non load-carrying joint based on nominal stress. So we have conducted that the fatigue strength of a welded joint with different geometry from the non stress distribution along the expected crack path.

• Structural Engineering and Mechanics
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• v.5 no.6
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• pp.743-754
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• 1997

A three-dimensional constitutive modeling for reinforced concrete is presented for finite element nonlinear analysis of reinforced concrete. The targets of interest to the authors are columns confined by lateral steel hoops, RC thin shells subjected to combined in-plane and out-of-plane actions and massive structures of three-dimensional (3D) extent in shear. The elasto-plastic and continuum fracture law is applied to pre-cracked solid concrete. For post cracking formulation, fixed multi-directional smeared crack model is adopted for RC domains of 3D geometry subjected to monotonic and reversed cyclic actions. The authors propose a new scheme of decomposing stress strain fields into sub-planes on which 2D constitutive laws can be applied. The proposed model for 3D reinforced concrete is experimentally verified in both member and structural levels under cyclic actions.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.173-180
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• 2002

The specimens with three discontinuities have been tested in uniaxial compression. The geometry of discontinuities is changed by three different parameters: flaw inclination angle, continuity, and spacing. From the tips of the discontinuities wing and secondary cracks are observed. Wing cracks initially propagate curvilinear direction and follow loading direction after some distance from the tip of the discontinuities. Two different types of secondary cracks have been observed from the study: quasi-coplanar secondary cracks and oblique secondary cracks. From the test nine different types of coalescence are observed and they show a correlation with flaw angle and ligament angle. It is attempted to simulate the observed results by using FROCK(Fractured ROCK). FROCK is a code based on the hybridized DDM(Displacement Discontinuities Method) . It is shown that FROCK has quite potential of modeling of rock fracture processes.