• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.9
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• pp.2894-2900
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• 1996

The stream generator tubes represent an integral part of a major barrier against the fission product release to the environment. So, the rupture of these tubes could permit flow of reactor coolant into the secondary system and injure the safety of reactor coolant system. Therefore, if the crack was detected during In-Service Inspection of tubes the cracked tube should be evaluated by the pulgging criteria and plugged or not. In this study, the fracture mechanics evaluation is carried out on the thru-wall axial crack due to Primary Water Stress Corrosion Cracking in the roll transition aone of steam generator tube to help the assurence the integrity of tubes and estabilish the plugging criteria. Due to the Inconel which is used as tube material is more ductile than others, the plastic instability repture theory was used to calculate the critical and allowable crack length. Based on Leak Before Break concept the leak rate for the critical crack length and the allowable leak rate are compared and the safety of tubes was given.

• Korean Journal of Construction Engineering and Management
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• v.11 no.6
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• pp.111-121
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• 2010

As the customer's interest for sidewalk block in the street or apartment complex is increasing, the materials of block which had been a concrete block exclusively are varied to clay paver, native rock and wood etc. Especially, the sales volume of clay paver which is environment-friendly and ergonomic is dramatically increasing every year with two digits growth rate, however, many problems like "Edge Cracking" "Freezing Breakage" "Bending Breakage" "Joint Gap" are happening frequently within a couple of hours after installation due to the durabilities. Because of the characteristics of Ceramic products, clay pavers are very easy to be broken when they are bumped against each other. In addition, they are relatively fragile by a freezing expansion breakage when exposed to water due to hydrophilic property as well as the intensity and absorptance of the products are varied with small difference from the production process such as production equipment and process control. Therefore, it costs a lot of money to repair the breakdown unless production and installation is carried out according to the strict criteria of the quality control. In this study, the symptoms of breakdown frequently happened in clay paver are classified by each type and finally the solution for this problem in the production of brick, installation and criteria of quality control through compressive strength and absorptance test is suggested.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.3
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• pp.31-38
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• 1989

This paper concentrates on the analysis of reinforced concrete(R/C) structures subjected to monotonic loading, from zero to ultimate loads. Tensile cracking, the nonlinear stress-strain relationship for concrete and reinforcement are taken into account the concrete is assumed to be elastic in tension region and elasto-hardening plastic in compression region. The Kupfer's failure criteria and associated flow rule are adopted to govern the plastic behavior of the concrete. The reinforcing bar is considered as a elasto-hardening platic material. The tension stiffening effect of the concrete between cracks is also considered. The numerical error depends on the used finite element mesh size is reduced by correcting the slope of strain softening region of the concrete according to the developed energy criteria.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.155-160
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• 2001

This paper describes a probabilistic fracture mechanics (PFM) analysis based on Monte Carlo (MC) simulation. In the analysis of CANDU pressure tube, it is necessary to perform the PFM analyses based on statistical consideration of flaw generation time. A depth and an aspect ratio of initial semi-elliptical surface crack, a fracture toughness value, delayed hydride cracking (DHC) velocity, and flaw generation time are assumed to be probabilistic variables. In all the analyses, degradation of fracture toughness due to neutron irradiation is considered. Also, the failure criteria considered are plastic collapse, unstable fracture and crack penetration. For the crack growth by DHC, the failure probability was evaluated in due consideration of flaw generation time.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.153-160
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• 2003

Nonlinear finite element analysis of reinforced concrete panels subjected to biaxial tensile loads are carried out by using a 9-node assumed strain shell element. The present study mainly focuses on the performance evaluation of material models such as cracking criteria, tension stiffening model and steel model in the membrane energy dominant situation. From numerical results, the exponential form of tension stiffening model together with the use of average yield stress model for the steel embedded in the concrete performs well in the panel analysis under biaxial tensile loading condition and it produces a good agreement with experiment results. Finally, the present results are provided as a benchmark test for reinforced concrete panel structures.

• Journal of Ocean Engineering and Technology
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• v.11 no.1
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• pp.16-23
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• 1997

Stainless steel are widely applicable in various engineering fields for its exellent corrosion and impact ressistance. Austenitic weld metal has some ferrite for preventing solidification cracking by ASME specification. Several family of austenic stainless steel contains varying ferrite contents. But ferrite in austenic stainless steels is adversely affect weld metal toughness and since fully austenic grades are known to have good toughness. Austenic stainless steel has various alloying addition for improving corrosion resistance, impact toughness and solidification crack resistance. The effect of various alloying elements are not found to be clear in present. From this view of point, this study tried to establish the criteria of alloy design for austenic stainless steel by controlling primary solidification mode and clarifying the effect of several alloying elements.

• Architectural research
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• v.16 no.1
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• pp.27-35
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• 2014

Nonlinear analysis of reinforced concrete structures is carried out by using Reissner-Mindlin (RM) shell finite element (FE). The brittle inelastic characteristic of concrete material is represented by using the elasto-plastic fracture (EPF) material model with the relevant material models such as cracking criteria, shear transfer model and tension stiffening model. In particular, assumed strains are introduced in the formulation of the present shell FE in order to avoid element deficiencies inherited in the standard RM shell FE. The arc-length control method is used to trace the full load-displacement path of reinforced concrete structures. Finally, four benchmark tests are carried out and numerical results are provided as future reference solutions produced by RM shell element with assumed strains.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.569-576
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• 2003

Fundamental issues in static finite element analysis of reinforced concrete panel subjected to biaxial tensile loads are discussed. This paper is trying to bring our attention to the appropriate use of concrete material models such as cracking criteria, tension stiffening model and the steel models which are basically used in the nonlinear finite element analysis of reinforced concrete panels. We mainly investigate the sensitivity of available material models and finite element technologies to the finite element analysis result using our recent reinforced concrete panel experiment result. Throughout this study, we found that the judicious use of the material models and finite element technologies with the sound understanding of structural characteristics can only guarantee the accurate prediction of panel behaviour.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.324-329
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• 2004

In this study, an application of crack morphology variables in the Leak-Before-Break(LBB) evaluation for nuclear piping systems is investigated, including influences on the leakage crack size and crack instability loads. The crack surface roughness and the number of flow turns as a function of the crack opening displacement are applied to LBB evaluations for KSNP pressurizer surge line, for which fatigue and stress corrosion cracking are considered as failure mechanisms. As a result, there would be a significant impact on safety margins to acceptance criteria for the surge line if crack morphology variables are applied additionally to the current regulatory guide without re-analyses for justification of safety factors being applied on the leakage crack size and piping loads for evaluations.

• Steel and Composite Structures
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• v.17 no.2
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• pp.159-172
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• 2014

A finite element model with the consideration of damage initiation and evolution has been developed for the analysis of the dynamic response of a composite sandwich panel subject to low velocity impact. Typical damage modes including fiber breakage, matrix crushing and cracking, delamination and core crushing are considered in this model. Strain-based Hashin failure criteria with stiffness degradation mechanism are used in predicting the initiation and evolution of intra-laminar damage modes by self-developed VUMAT subroutine. Zero-thickness cohesive elements are adopted along the interface regions between the facesheets and the foam core to simulate the initiation and propagation of delamination. A crushable foam core model with volumetric hardening rule is used to simulate the mechanical behavior of foam core material at the plastic state. The time history curves of contact force and the core collapse area are obtained. They all show a good correlation with the experimental data.