• Structural Engineering and Mechanics
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• v.5 no.5
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• pp.587-598
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• 1997

A numerical model for masonry is proposed by following an internal variable approach originally developed in the field of elastic-plastic analysis. The general features of the theoretical framework are discussed by focussing on finite element models applicable to incremental elastic-plastic problems. An extremum property is derived and its implications in terms of convergence for convenient algorithms are briefly discussed, by including the case of softening materials and damage effects. Next, a numerical model is presented, which is suitable for masonry, can be developed according to the same internal variable formulation and enjoys similar properties. Some numerical results are presented and compared with the response of a masonry shear wall subjected to pseudodynamic tests.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.812-815
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• 2002

The shape of K-R curve for an ideally brittle material is flat because the surface energy is an unvaried material property. However, the K-R curve can take on a variety of shapes when nonlinear material behavior accompanies fracture. By the way, a general metallic material is nonlinear, structural steel is such. Therefore, the J-R curve form J-integral value instead of K parameters can be used to evaluate elastic-plastic materials with flaws in terms of ductile fracture that can be significant to design. In this paper, R-curve behaviors form K and J parameter is considered for the precise assessment of fracture analysis, in case of JS-SS400 steels.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.4253-4258
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• 2012

The investigation of the undrained strength and the important several undrained geotechnical properties was, in detail, made for highly plastic soils using the field and laboratory testing results. The plastic index, activity, water content, and effective unit weight did not show the notable relationship with both Su and normalized Su. The OCR, sensitivity, and undrained elastic modulus presented remarkable tendency with normalized Su. It could be concluded that the use of the normalized Su may lead to the reasonable results then the normalized Su needs further research.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.6
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• pp.542-546
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• 2005

The J-integral used as a ductile crack initiation criterion has been discussed for the impact loaded elastic-plastic 3PB specimens. The experimental method to measure or estimate the J-integral history has been investigated and its result has been compared to the obtained elastic-plastic values by the finite element model of this study. These numerical results and the experimental curves are found to agree closely. J-integral can be calculated by only numerical analysis with the finite element model. It is proved that simple calculation can be made in order to find the possible value of J-integral by crack mouth opening displacement(CMOD) in the dynamic nonlinear fracture experiment of 3-point bend(3PB) specimen. The property of elastic-plastic material is considered at different impact velocities. The J-integral may be estimated from the crack mouth opening displacement which can be measured directly kom photographs taken during impact experiments.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.837-842
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• 2000

In the coiling process of helical steam generator tubes of integral reactor SMART, a considerable amount of spring back, which induces dimensional inaccuracy and difficulty in fabrication, has been arised. In this research, an analytical model was derived to evaluate the amount of the spring back for steam generator tubes. The model was developed on the basis of beam theory and elastic-perfectly plastic material property. This model was extended to consider the effect of plastic hardening and the effect of the tensile force on the spring back phenomena. Parametric studies were performed for various design variables of steam generator tubes in order to minimize the spring back in the design stage. A sensitivity analysis has shown that the low yield strength, the high elastic modulus, the small helix diameter, and the large tube diameter result in a small amount of the spring back. The amount of the spring back can be controlled by the selection of adequate design values in the basic design stage and reduced to an allowable limit by the application of the tensile force to the tube during the coiling process.

• Proceedings of the Korean Nuclear Society Conference
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• 1999.10a
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• pp.355.2-355
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• 1999

The spnng back phenomena occurring in the coiling process of a steam generator tube induces the dimensional inaccuracy and makes the coiling procedure difficult. In this research, an analytical model was developed to evaluate the amount of the spring back for SMART steam generator tubes. The model was developed on the basis of beam theory and elastic-perfectly plastic material property. This model was extended to consider the effect of plastic hardening and the effect of the tensile force on the spring back phenomena. Parametric studies were performed for various design variables of steam generator tubes in order to minimize the spring back in the design stage. A sensitivity analysis has shown that the low yield strength, the high elastic modulus, the small helix diameter, and the large tube diameter result in a small amount of the spring back. The amount of the spring back can be controlled by the selection of adequate design values in the basic design stage and reduced to an allowable limit by the application of the tensile force to the tube during the coiling process.rocess.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.10
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• pp.1869-1876
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• 1992

The effect of particle property on FOD(foreign object damage) and strength degradation in structural ceramics especially, silicon carbide was investigated by accelerating a spherical particle having different material and different size. The damage induced showed significant differences in their patterns with increase of impact velocity. Also percussion cone was formed at the back part of specimen when particle size became large and its impact velocity exceeded a critical value. The extent of ring cracks was linearly related to particle size, however the impact of steel particle produced larger ring cracks than that of SiC particle. Increasing impact velocity the residual strength showed different degradation behaviors according to particle and its size. In the region the impact site represents nearly elastic deformation behavior, the residual strength was dependent upon the depth of cone crack regardless of particle size. However in elastic- plastic deformation region, the radial cracks led to rapid drop in residual strength.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.167-173
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• 2005

The Berkovich nano-indentation is an indentation test method analyzing mechanical properties of materials such as hardness and elastic modulus. The length scale of the penetration is measured in nanometers. Therefore, this method becomes widely useful for analyzing the mechanical property of thin film which can not be measured before. In this paper, comparing two results of the load-displacement curve obtained by the Berkovich nano-indentation and the 3-D finite element analysis, it was confirmed that the 3-D finite element analysis is useful. The phenomenon of pile-up and sink-in due to material properties was discussed by the finite element analysis.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.2
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• pp.134-140
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• 1994

Numerical caiculations are made in order to find a possible relation between the J-integral and the crack mouth opening displacement(CMOD) in dynamic nonlinear fracture experiments. Both elastic-plastic and elastic-viscoplastic materials are considered at different impact velocities. The J-integral may be estimated from the crack mouth opening displacement which can be measured directiy from photographs taken during dynamic experiments.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.10
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• pp.805-816
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• 2008

The present work reviews the methods to evaluate elastic-plastic material characteristics by indentation tests. Especially the representative stress and strain values used in some papers are critically analyzed. The values should not only represent the load-depth curve, but also represent the whole of deformed material around the impression. We briefly introduce other indentation techniques to evaluate residual stresses, creep properties, and fracture toughness. We also review some technical problems that are related to the accuracy issues in indentation tests.