• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.3
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• pp.259-266
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• 2004

Detailed two-dimensional and three-dimensional finite element (FE) analyses of double-edge cracked tension (DE(T)) specimens are carried out to investigate the effect of the relative crack length and the thickness on experimental J testing schemes. Finite element analyses involve systematic variations of relevant parameters, such as the relative crack depth and plate width-to-thickness ratio. Furthermore, the strain hardening index of material is systematically varied, including perfectly plastic (non-hardening) cases. Based on FE results, a robust experimental J estimation scheme is proposed.

• Transactions of Materials Processing
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• v.16 no.4 s.94
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• pp.317-322
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• 2007

In order to investigate the cause and condition of fluting in tangential bending of low carbon steel sheet, an analytic analysis, an experiment and a series of finite element analysis for bending process were done. The fluting in bended sheet was related with the yield point elongation of material. Due to the yield point elongation, unstable plastic hinge was occurred in course of bending of elastic perfectly plastic sheet. According to the analysis and computational results, lower yield point elongation than 5% was required to prevent fluting in 0.5-0.6t sheet in $15{\sim}25mm$ radius bending. The tendency of fluting occurrence was reduced as decreasing the radius of bending, increasing thickness of bended sheet, and removing irregularity in sheet and bending processes.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.10a
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• pp.217-224
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• 1997

One way in which a comparison can be mode between various reinforced concrete structures is to compare the rate of energy absorption capacity. It is useful to use a well-known standard hysteretic rule as a benchmark for comparisons. The concept of energy absorption efficiency with respect to an elaste-perfectly plastic (EPP) system has been adopted. The normalized cumulative energy, cumulative plastic drift and energy response spectra are used for the method. The previous study using the energy spectra developed by Chang and Mander (1994) indicates the cumulative plastic demand for most earthquakes to be 0.1 rad., but a conservative upper bound of 0.2 rad. could be expected for a maximum credible earthquake. From the present study, the energy absorption efficiency in R.C. structures with respect to the EPP system may range in 30%-45% for most cases.

• Structural Engineering and Mechanics
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• v.7 no.3
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• pp.331-344
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• 1999

This paper provides an analysis of the transient behaviour of a right-angled bent cantilever beam subjected to a suddenly applied force at its tip perpendicular to its plane. Based on a rigid, perfectly plastic material model, a double-hinge mechanism is required to complete the possible deformation under a rectangular force pulse (constant force applied for a finite duration) with a four-phase response mode. The kinematics of the various response phases are described and the partitioning of the input energy at the plastic hinges during the motion is evaluated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.5
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• pp.562-569
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• 2007

This paper presents plastic limit loads and approximate J estimates for axial through-wall cracked pipe bends under internal pressure and in-plane bending. Geometric variables associated with a crack and pipe bend are systematically varied, and three possible crack locations (intrados, extrados and crown) in pipe bends are considered. Based on small strain finite element limit analyses using elastic-perfectly plastic materials, effect of bend and crack geometries on plastic limit loads for axial through-wall cracked pipe bends under internal pressure and in-plane bending are quantified, and closed-form limit solutions are given. Based on proposed limit load solutions, a J estimation scheme for axial through-wall cracked pipe bends under internal pressure and in-plane bending is proposed based on reference stress approach.

• Geomechanics and Engineering
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• v.18 no.3
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• pp.225-234
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• 2019

A numerical stepwise approach for cavity expansion problem in strain-softening rock or soil mass is investigated, which is compatible with Mohr-Coulomb and generalized Hoek-Brown failure criteria. Based on finite difference method, plastic region is divided into a finite number of concentric rings whose thicknesses are determined internally to satisfy the equilibrium and compatibility equations, the material parameters of the rock or soil mass are assumed to be the same in each ring. For the strain-softening behavior, the strength parameters are assumed to be a linear function of deviatoric plastic strain (${\gamma}p^*$) for each ring. Increments of stress and strain for each ring are calculated with the finite difference method. Assumptions of large-strain for soil mass and small-strain for rock mass are adopted, respectively. A new numerical stepwise approach for limited pressure and plastic radius are obtained. Comparisons are conducted to validate the correctness of the proposed approach with Vesic's solution (1972). The results show that the perfectly elasto-plastic model may underestimate the displacement and stresses in cavity expansion than strain-softening coefficient considered. The results of limit expansion pressure based on the generalised H-B failure criterion are less than those obtained based on the M-C failure criterion.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.475-478
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• 1999

A numerical tool for predicting the behavior of reinforced concrete structures under uniaxial loads is proposed. Concrete is considered as quasi-brittle material, and for a reinforcing bar, an elastic-perfectly plastic constitutive relationship is adopted. In this study, the behavior of reinforced concrete according to the interface properties between the concrete and steel is analyzed. Comparisons between the numerical predictions and the experimental results show good agreements in the load-deflection behaviors and ultimate loads of reinforced concrete structures.

• Nuclear Engineering and Technology
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• v.29 no.2
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• pp.138-147
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• 1997

Korean-made alloys 600 and 690 tubes were evaluated by flare tests according to ASTM standards, and acting stresses during the test ore analyzed. All the tubes, including alloys 600 and 690 tubes with various heat treatment conditions, satisfied the requirement with 30 or 35750.D expansion. Axial stresses in alloy 690 tubes were higher than those in alloy 600 ones and the gap increased gradually with flaring percentage(F.P, %). Assuming the tubes as the rigid-perfectly plastic body, a stress equation was obtained using modified Tresca's yield criterion. Also microstructural change of the flared tubes was discussed with the acting stresses.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.155-162
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• 2003

The evolved energy concept has been demonstrated to fir the seismic evaluation of various steel connection details with the objective basis. For this, the strain energy stored in the structural system obtained from the experimental database has been normalized by that of a benchmark system. In this notion, the ideal elastic-perfectly plastic structural system has been assumed as a benchmark. In addition, the attempt shows that those previously peformed experimental database can be recycled to have further significance.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1772-1777
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• 2007

This paper provides plastic limit loads of pipes with constant-depth, circumferential part-through surface cracks under combined pressure and bending. A key issue is to postulate discontinuous hoop stress distributions in the net-section. Validity of the proposed limit load solutions is checked against the results from three-dimensional (3-D) finite element (FE) limit analyses using elastic-perfectly plastic material behavior.