• Proceedings of the KWS Conference
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• 2002.10a
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• pp.396-401
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• 2002

A practical method for evaluating the possibility of the occurrence of cracking in actual thick-plate T-joint weldments is presented in this study. Systematic experiments based on the method of the design of experiment are conducted in order to investigate the crack tendency in relation to typical welding parameters such as diffusible hydrogen, restraint intensity, preheating temperature and so on. The elastic analysis using the [mite element techniques is employed to quantify the restraint intensities of the specimens. The defined restraint intensities are treated in numerical way for the sake of considering the most uncertain factor among some major factors that govern the cracking phenomena due to welding. The critical plane for judgment of the crack occurrence or crack density is presented as a function of typical welding parameters including determined restraint intensities. The results of numerical estimation by the proposed method for the experimental specimens show the usefulness as a practical tool in welding induced crack problem having extensive uncertainties.

• Journal of the Korea Concrete Institute
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• v.12 no.6
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• pp.109-117
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• 2000

CFRD(Concrete Faced Rockfill Dam) face slab concrete has a much capability to occur crack due to drying shrinkage, plastic shrinkage and bad compaction etc. Because of these cracks of concrete induce structural problem and decrease durability of dam, it is need to reduce crack of face slab concrete. This is an experimental study to analyze the influence factors on crack properties of CFRD face slab concrete. For this purpose, various mix proportion of CFRD face slab concrete and concrete using PPF(polypropylene fiber0 and fly ash was selected. And tests for drying shrinkage, bonding strength, water permeability and plastic shrinkage were performed, and then CFRD D and PPC of those mix proportion were placed in CFRD field. According to test results, it was found that the bonding strength of C1(compact sufficiently) was higher about 10~20% than that of C2(compact insufficiently). And the engineering properties of PPC(concrete using PPF) and FAC(concrete using fly ash) were better than those of the others ; the permeability of PPC and FAC after 8 weeks curing was little lower than that of CFRD D, and plastic shrinkage crack of PPC and FAC was lower 40~60% than crack of CFRD D.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.5
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• pp.823-833
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• 2001

In recent years, the subject of remaining life assessment has drawn considerable attention in chemical plants, where various structural components typically operate at high temperature an pressure. Thus a life prediction methodology accounting for high temperature creep fracture is increasingly needed for the components. Critical defects in such structures are generally found in the form of semi-elliptical surface crack, and the analysis of which is consequently an important problem in engineering fracture mechanics. On this background, we first develop an auto mesh generation program for detailed 3-D finite element analyses of axial and circumferential semi-elliptical surface cracks in a piping system. A high temperature creep fracture parameter C-integral is obtained from the finite element analyses of generated 3-D models. Post crack growth module is further appended here to calculate the amount of crack growth. Finally the remaining lives of surface cracked pipes for various analytical parameters are assessed using the developed life assessment program.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.487-492
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• 2007

The enhancement of the service life of damaged or cracked structures is a major issue for researchers and engineers. The hierarchical void element with the integrals of Legend polynomials is used to characterize the fracture behavior of unpatched crack as well as repaired crack with bonded composite patches by computing the stress intensity factors and stress contours at the crack tip. The numerical approach is based on the v-version degenerate shell element including the theory of anisotropic laminated composites. Since the equivalent single layer approach is adopted in this study, the proposed element is necessary to represent a discontinuous crack part as a continuum body with zero stiffness of materials. Thus the aspect ratio of this element to represent the crack should be extremely slender. The sensitivity of numerical solution with respect to energy release rate, displacement and stress has been tested to show the robustness of hierarchical void element as the aspect ratio is increased up to 2000. The stiffness derivative method and displacement extrapolation method have been applied to calculate the stress intensity factors of Mode I problem.

• Journal of the Korea Institute of Building Construction
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• v.6 no.2 s.20
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• pp.91-98
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• 2006

The purpose of this study is to investigate the problem of crack repair materials and methods in existing concrete structure and to propose the effective injection method on crack repair by packer type. The result of this study is as follows. It is investigated that the crack width in the inner matrix of concrete structure is decreased about 30-40% than that in the sulfate of the concrete structure. Also it is showed that the possibility which could be monolithic with injection part became higher if the injection part if installed near to surface of concrete on the punching method to vertical direction against crack area. The injection of repair material can be poured smoothly under about $10N/mm^2$ pressure on the condition that cracks are monolithic with injection part without dust by drill. The effective method to pour the injection repair material is the punching method by coredrill but several research to minimize injection pressure should be continually.

• International Journal of Korean Welding Society
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• v.4 no.1
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• pp.38-45
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• 2004

A practical method for evaluating the possibility of the occurrence of cracking in actual thick-plate T-joint weldments is presented in this study. Systematic experitrients based on the method of the design of experiment are conducted in order to investigate the crack tendency in relation to typical welding parameters such as diffusible hydrogen, restraint intensity, preheating temperature and so on. The elastic analysis using the fmite element techniques is employed to quantify the restraint intensities of the specimens. The defined restraint intensities are treated in numerical way for the sake of considering the most uncertain factor among some major factors that govern the cracking phenomena due to welding. The critical plane for judgment of the crack occurrence or crack density is presented as a function of typical welding parameters including determined restraint intensities. The results of numerical estimation by the proposed method for the experimental specimens show the usefulness as a practical tool in welding induced crack problem having extensive uncertainties.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.5
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• pp.828-834
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• 2002

In this paper, for the mixed mode fatigue problem, the method of determining testing load was proposed. It is based on the plastic zone size and the limited maximum stress intensity factor by ASTM STANDARD E 647-00. The application method of maximum tangential stress criterion and the stress intensity factor for the finite width specimen was proposed. In the result of applying the method to mixed mode fat gut test for A5052 H34, it obtained the satisfactory experimental results on the stable crack growth.

• Steel and Composite Structures
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• v.16 no.2
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• pp.203-220
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• 2014

Stress intensity factors are numerically investigated for interfacial edge crack between two dissimilar composite plates jointed with single side composite patch. Variation of stress intensity factor under Mode I loading condition is examined for different material models and fiber orientation angles of composite plates and patch. ANSYS 12.1 finite element analysis software is used to obtain displacements of crack surfaces in the numerical solution and repaired plates are modeled in three dimensions. Obtained results are presented in the form of graphs. It is found that fiber orientation angle of composites is an effective parameter on interfacial stress intensity factor.

• Journal of applied mathematics & informatics
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• v.8 no.1
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• pp.59-69
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• 2001

The paper deals with the interaction between three Griffith cracks propagating under antiplane shear stress at the interface of two dissimilar infinite elastic half-spaces. The Fourier transform technique is used to reduce the elastodynamic problem to the solution of a set of integral equations which has been solved by using the finite Hilbert transform technique and Cooke’s result. The analytical expressions for the stress intensity factors at the crack tips are obtained. Numerical values of the interaction efect have been computed for and results show that interaction effects are either shielding or amplification depending on the location of each crack with respect to other and crack tip spacing. AMS Mathematics Subject Classification : 73M25.

• Journal of Mechanical Science and Technology
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• v.18 no.9
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• pp.1582-1589
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• 2004

The dynamic response of an eccentric Griffith crack in functionally graded piezoelectric ceramic strip under anti-plane shear impact loading is ana lysed using integral transform method. Laplace transform and Fourier transform are used to reduce the problem to two pairs of dual integral equations, which are then expressed to Fredholm integral equations of the second kind. We assume that the properties of the functionally graded piezoelectric material vary continuously along the thickness. The impermeable crack boundary condition is adopted. Numerical values on the dynamic stress intensity factors are presented for the functionally graded piezoelectric material to show the dependence of the gradient of material properties and electric loadings.