• Structural Engineering and Mechanics
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• v.3 no.1
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• pp.35-48
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• 1995

This paper presents new frequency results for elliptical and semi-elliptical Mindlin plates of various aspect ratios, thicknesses and boundary conditions. The results were obtained using the recently developed computerized Rayleigh-Ritz method for thick plate analysis. For simply supported elliptical plates, it is proposed that the penalty function method be used to enforce the condition of zero rotation of the midplane normal in the tangent plane to the plate boundary.

• Steel and Composite Structures
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• v.34 no.2
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• pp.227-239
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• 2020

The aim of this study is to obtain the nonlinear and post-buckling responses of relatively thick functionally graded plates with oblique elliptical cutouts using a new semi-analytical approach. To model the oblique elliptical hole in a FGM plate, six plate-elements are used and the connection between these elements is provided by the well-known Penalty method. Therefore, the semi-analytical technique used in this paper is known as the plate assembly technique. In order to take into account for functionality of the material in a perforated plate, the volume fraction of the material constituents follows a simple power law distribution. Since the FGM perforated plates are relatively thick in this research, the structural model is assumed to be the first order shear deformation theory and Von-Karman's assumptions are used to incorporate geometric nonlinearity. The equilibrium equations for FGM plates containing elliptical holes are obtained by the principle of minimum of total potential energy. The obtained nonlinear equilibrium equations are solved numerically using the quadratic extrapolation technique. Various sets of boundary conditions for FGM plates and different cutout sizes and orientations are assumed here and their effects on nonlinear response of plates under compressive loads are examined.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.5
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• pp.1229-1242
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• 1995

The thermal shock stress intensity factors of semi-elliptical surface crack in finite plate and the stress intensity fractors of embedded elliptical crack in turbine rotor is determined by means of Vainshtok weight function method. In case of semi-elliptical surface crack, the solution is compared with previous solution. The stress intensity factor for embedded elliptical crack in turbine rotor loaded by centrifugal and thermal loading is also determined. In this case, the value of stress intensity factor is larger at crack contour near internal radius surface and is almost constant at the crack contour farther from internal radius surface.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.126-137
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• 2003

Many research works have been performed on the J-T approach for elastic-plastic crack-tip stress fields in a variety of plane strain specimens. To generalize the validity of J-T method, further investigations are however needed fur more practical 3D structures than the idealized plane strain specimens. The present study deals mainly with 3D finite element (FE) modeling of welded plate and straight pipe, and accompanying elastic, elastic-plastic FE analyses. Manual 3D modeling is almost prohibitive, since the models contain semi-elliptical interfacial cracks which require singular elements. To overcome this kind of barrier, we develop a program generating the meshes fur semi-elliptical interfacial cracks. We then compare the detailed 3D FE stress fields to those predicted with J-T two parameters. The validity of J-T approach is thereby extended to 3D yield-strength-mismatched weld joints, and useful information is inferred fur the design or assessment of pipe welds.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1250-1261
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• 2002

Many research works have validated the J-T approach to elastic-plastic crack-tip stress fields in a variety of plane strain specimens. To generalize the validity of J-T method, further investigations are however needed for more practical 3D structures than the idealized plane strain specimens. In this work, we perform 3D finite element (FE) modeling of welded plate and straight pipe, and accompanying elastic, elastic-plastic FE analyses. Manual 3D modeling is almost prohibitive, since the models contain semi-elliptical interfacial cracks which require singular elements. To overcome this kind of barrier, we develop a program generating the meshes for semi-elliptical interfacial cracks. We then compare the detailed 3D FE stress fields to those predicted with J-T two parameters. Thereby we extend the validity of J-T application to 3D structures and infer some useful informations for the design or assessment of pipe welds.

• Journal of Ocean Engineering and Technology
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• v.11 no.3
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• pp.20-28
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• 1997

The fatigue crack propagation properties and fatigue life of two kinds of Al body panel for automobile were examined experimentally by using the plate specimen and the single spot welding specimen. The fatigue limit of spot welding specimens was lower than that of a plate specimen. The fatigue limit was similar in two kinds of spot welding specimen. The shape and size of crack propagation were observed and measured on beach mark of fracture surface. The crack propagation of surface crack specimen showed almost same tendency to that of a thick plate as almost semi-elliptical. In spot welding specimen, the fatigue crack occurred in inside surface of nugget area was almost semi-elliptical. The crack growth rate can be explained using equation of stress intensity factors.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.2022-2032
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• 1999

In recent years, the subject of remaining life assessment has drawn considerable attention in the power generation industry. In power generation systems a variety of structural components, such as steam pipes, turbine rotors, and superheater headers, typically operate at high temperatures and high pressures. Thus a life prediction methodology accounting for fracture and rupture is increasingly needed for these components. For accurate failure assessment, in addition to the single parameter such as K or J-integral used in traditional fracture mechanics, the second parameter like T-stress describing the constraint is needed. The most critical defects in such structures are generally found in the form of semi-elliptical surface cracks in the welded piping-joints. In this work, selecting the structures of surface-cracked plate and straight pipe, we first perform line-spring finite element modeling, and accompanying elastic-plastic finite element analyses. We then present a framework for including constraint effects (T-stress effects) in the R6 failure assessment diagram approach for fracture assessment.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.649-659
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• 2002

For a variety of elastic-plastic stress fields of plane strain specimens, many research works verified the validity of J-T approach. To generalize the validity of J-T method, however, further investigations are needed for more practical 3D structures than the idealized geometries as plane strain specimens. In this work, selecting two main types of structures such as plate and straight pipe, we perform 3D finite element(FE) modeling, and accompanying elastic, elastic-plastic FE analyses. We then study the validity of J-T application to 3D structures, and present some useful informations for the design or assessment of pipe welds by comparing the stress fields from the detailed 3D FE analyses to those predicted with J-T two parameters.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3295-3300
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• 2012

Three Dimensional finite element method (FEM) was used to obtain the stress intensity factor for subsurface cracks and surface cracks existing in inhomogeneous materials. A geometry model, i.e. a solid containing one or several 3D cracks is defined. Several distributions of local node density are chosen, and then automatically superposed on one another over the geometry model. Nodes are generated by the bubble packing, and ten-noded quadratic tetrahedral solid elements are generated by the Delaunay triangulation techniques. To examine accuracy and efficiency of the present system, the stress intensity factor for a semi-elliptical surface crack in a plate subjected to uniform tension is calculated, and compared with Raju-Newman's solutions. Then the system is applied to analyze interaction effects of two dissimilar semi-elliptical cracks in a plate subjected to uniform tension.

• Bulletin of the Society of Naval Architects of Korea
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• v.13 no.4
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• pp.1-10
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• 1976

It is a well-known phenomenon that, in the case of vibrations of an elastic body in a fluid such as water, the presence of the surrounding fluid has the effect of lowering the natural frequencies of the vibration as compared with those in air or vacuum on account of the increased inertia, i.e. added mass. In this report, defining the mass increase factor as the ratio of added mass to vibration mass of the body in air, the author investigated the mass increased factor of an elastic plate vibrating in the fluid. It is assumed that the edges of the plate are simply supported, and that the surrounding fluid is an infinite ideal one. For the problem formulation the elliptical cylindrical coordinate system is adopted, so that a rectangular plate may be represented by a sheet degenerated from an elliptical cylinder. By virtue of the coordinate system adopted, plates which are chordwisely finite and lengthwisely contineous could directly be treated, but plates which are chordwisely finite in both directions could not be treated directly. For the latter, hence, plates which are chordwisely finite and lengthwisely semi-finite are investigated as an appropriate approximation. Some examples of the mass increase factor are numerically calculated for the fundamental mode and modes of zero or one nodal line in each direction with the range of the aspect ratio from 1 to 10 or more.