• Journal of the Korean Society for Railway
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• v.11 no.3
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• pp.280-285
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• 2008

Two kinds of failure model, that is, the Gurson model and a shear failure model were used for the finite element analyses of simple and notch tensile specimens and axial compression of a fracture tube with initial saw-cuts. The parameter values for the shear failure model were determined by a combined experimental and numerical analysis of the notch tensile specimens. After fitting the numerical parameters such as the yielding stress and the fracture shear strains, the Gurson model and the shear failure model were applied to the analysis of the fracture tube. Although the Gurson model and the shear failure model showed similar fracture behavior for the case of the tensile specimens, the respective results were different in the axial force and the crack growth rate of the fracture tube. That is, the shear failure model required more axial force to make the cracks propagate along the tube than the Gurson model. These are believed to show the lack of damage evolution process of the shear failure model. To decide which model is better in the tube analysis, experimental verification will be necessary.

• 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 Korean Society of Machine Tool Engineers Conference
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• 1998.10a
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• pp.248-253
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• 1998

Recently, the uses of Ceramic/metal bonded joints, resin/metal joints, adhesive joints, composite materials which are composed of dissimiliar materials have increased in various industry fields. Since the ceramic/metal bonded joints material is made at a high temperature, residual stress distributions due to differences in material properties were investigated by varying material parameters. The two dimensional finite element analysis was performed to study residual stress distribution in Si3N4/SM45C bonded joint with a copper interlayer between the silicon nitride(Si3N4) and the structural carbon steel(SM45C) and 4-point bending tests were carried out under room temperature. Fracture surface and crack propagation path were observed using scanning electron microscope and characteristics of its fracture was discussed.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.1
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• pp.103-111
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• 2012

This study reviews several fracture models for predicting the residual strength of notched composite laminates. Representative experimental results on the residual strength of composite laminates containing a notch subjected to static uniaxial tensile loading have been collected from open literature. And notched strength data for T300/5208 are analyzed. The various parameters associated with the fracture models have been determined for laminates. Notched strength data sets are compared with fracture models and the applicability of the different fracture models in predicting the notched strength of composite laminates is discussed. And static tests have been performed on 2.0mm depth notched specimen. And the test results are compared with analysis models.

• Computers and Concrete
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• v.1 no.2
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• pp.169-188
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• 2004

A coupled damage-viscoplasticity model is presented for the analysis of localisation and size effects. On one hand, viscosity helps to avoid mesh sensitivity because of the introduction of a length scale in the model and, on the other hand, enables to represent size effects. Size effects were analysed by means of three-point bending tests. Correlation between the fracture energy parameter measured experimentally and the density fracture energy modelling parameter is discussed. It has been shown that the dependence of nominal strength and fracture energy on size is determined by the ligament length in comparison with the width of the fracture process zone.

• Transactions of Materials Processing
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• v.5 no.1
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• pp.72-80
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• 1996

During the shape rolling process the influence of reduction ration and taper of shape roller on deformation and limit of ductile fracture such as free surface cracks developing in the workpiece has been studied. The deformation behaviours were analyzed by the 3-dimensional elasto-pastic finite element method and the conditions of ductile fracture were determined from 3-dimensional elasto-plastic finite element method and modified Cockrogt-Latham criterion. The deformed geometry and prediction of ductile fracture by 3-dimensional elasto-plastic finite element method are compared with experimental results The calcuated results are in good agreements with experimental data. The analysis used in the study was found to be effective in predicting the shape rolling process.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.155-158
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• 2005

Damage and fracture of concrete is characterized as the degradation of strength and stiffness. There can be modeled as the so-called homogenized crack model which can overcome the mesh sensitivity. But the plasticity and damage modeling for damage behavior before the fracture of concrete should be combined with the crack model. In this study, a damage function and an unified hardening-softening function are applied to the homogenized crack model to develope a 3-dimensional FEM program for nonlinear damage and fracture analysis of concrete. The comparison of numerical results and experimental data show that the combined modeling in this study can simulate the damage and fracture of concrete without the mesh-sensitivity. It is also shown that the behavior of the so-called Engineering Cementitious Composite(ECC) characterized by strain-hardening and multiple cracks can be well simulated using the modeling.

• Computational Structural Engineering
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• v.7 no.4
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• pp.113-118
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• 1994

The purpose of this study is elastic plastic finite element analysis for standard fracture toughness specimens. The principles of elastic-plastic fracture mechanics are shortly summarized and the special requirements for computational tools are derived. Possibilities to model the crack tip singularities are mentioned. The relevant fracture parameters like J-Integral and COD and their correlation are evaluated from elastic plastic finite element calculations of standard fracture toughnes specimens. The size and form of the plastic zone are shown. The comparion between experiment and caculation is discussed as well as the application of the limit load analysis.

• Biomaterials and Biomechanics in Bioengineering
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• v.3 no.1
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• pp.47-57
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• 2016

Results from multiple high profile experiments on the parameters influencing the impacts that cause skull fractures to the frontal, temporal, and parietal bones were gathered and analyzed. The location of the impact as a binary function of frontal or lateral strike, the velocity, the striking area of the impactor, and the force needed to cause skull fracture in each experiment were subjected to statistical analysis using the JMP statistical software pack. A novel neural network model predicting skull fracture threshold was developed with a high statistical correlation ($R^2=0.978$) and presented in this text. Despite variation within individual studies, the equation herein proposes a 3 kN greater resistance to fracture for the frontal bone when compared to the temporoparietal bones. Additionally, impacts with low velocities (<4.1 m/s) were more prone to cause fracture in the lateral regions of the skull when compared to similar velocity frontal impacts. Conversely, higher velocity impacts (>4.1 m/s) showed a greater frontal sensitivity.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.19 no.2
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• pp.117-129
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• 2023

Hydrogen embrittlement of a pipe is an important factor in hydrogen transport. To characterize hydrogen embrittlement, tensile and fracture toughness tests should be conducted. However, in the case of hydrogen-embrittled materials, it is difficult to perform tests in hydrogen environment, particularly at low temperatures. It would be useful to develop a methodology to predict the fracture toughness of hydrogen-embrittled materials at low temperatures using more efficient tests. In this study, the fracture toughness of API X52 steels in hydrogen at low temperatures is predicted from numerical simulation using coupled finite element (FE) damage analyses with FE diffusion analysis, calibrated by analyzing small punch test data.