• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.153-158
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• 1999

In the design and analysis of soil nailed slope, interaction between soil and nail is one of important problems. In the present analysis approaches for the interactions have developed a elastic analysis approach or a plastic analysis approach. However these approaches are not able to estimate the general interaction between soil and nail. In this study the general interaction between soil and nail using the strain wedge model is proposed. Also results of comparison between the proposed method and full scale test results by Gassler(1976) and large scale experimental results at Oxford University are shown in good agreements.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.378-385
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• 2000

Fracture resistance (J-R) curves, which are used for elastic-plastic fracture mechanics analyses, decreased under tension-compression loading condition. This phenomenon was proved by several former researches, but the causes have not been clear yet. The objective of this paper is to investigate the cause of this phenomenon. On the basis of fracture resistance curve test results, strain hardening hypothesis, stress redistribution hypothesis and crack opening hypothesis were built. In this study, hardness tests, Automated Ball Indentation(ABI) tests, theoretical stress field analyses, and crack opening analyses were performed to prove the hypotheses. From this study, strain-hardening of material, generation of tensile residual stress at crack tip, and crack opening effects are proved as the causes of the decrease hypothesis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.6 s.177
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• pp.1438-1445
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• 2000

To determine dynamic characteristics of materials, a program was developed under base of stress wave propagation theory for SHPB with explicit finite element method. Through the program, all kinds of quasi-static stress-strain curves can be directly converted to dynamic stress-strain curves at any strain rate. This simulation results were compared with experimental results in the references and they are in a good agreement with each other.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.1
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• pp.73-83
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• 1994

Press formabilities of aluminum sheets for automobile body were investigated. Plane strain stretching test (called RIST-PSST), cupping test and U bending test were performed to assess the press formability of aluminum sheets respectively. The results showed that aluminum sheets are generally inferior to cold-rolled steel sheet of deep drawing quality (CSP3N) in press formability. The limiting punch height (LPH) and limiting plane strain (FLCo) of aluminum sheets are 50%-70% level compared to that of CSP3N. Moreover, the limiting drawing ratios(LDR) of aluminum sheets are ranged between 1.95 and 2.1. The poor press formability of aluminum sheets is responsible for low values of total elongation and plastic anisotropy parameter in tensile characteristic. The shape fixability of aluminum sheets evaluated in U bending test is very poor due to its low elastic modulus compared to CSP3N.

• Geomechanics and Engineering
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• v.3 no.4
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• pp.323-337
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• 2011

Israel's coastal region consists, mainly, of Pleistocene and Holocene sands with varying degrees of calcareous cementation, known locally as "kurkar". Previous studies of these materials emphasized the difficulty in their geotechnical characterization, due to their extreme variability. Consequently, it is difficult to estimate construction stability, displacements and deformations on, or within these soils. It is suggested that SPT and Menard pressuremeter tests may be used to characterize the properties of these materials. Values of elastic modulus obtained from pressuremeter tests may be used for displacement analyses at different strain levels, while accounting for the geometric dimensions (length/diameter ratio) of the test probe. A relationship was obtained between pressuremeter modulus and SPT blow count, consistent with published data for footing settlements on granular soils. Cohesion values, for a known friction angle, are estimated, by comparing field pressuremeter curves to curves from numerical (finite element or finite difference) analyses. The material analyzed in the paper is shown to be strain-softening, with the initial cohesion degrading to zero on development of plastic shear strains.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.47-52
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• 2004

Springback comes from the release of residual stress after forming. The control of phenomenon is especially important in the sheet metal forming since there are no other practical methods available to correct the dimensional inaccuracy from springback. Therefore the accurate predication before the die machining has been a long goal in the Held of sheet metal forming. The aim of the present study is to enhance the prediction capability of finite element(FE) analysis for the springback phenomenon. For this purpose FE analysis for V-bending has been carried out with the commercial programs, LS-DYNA. The FE analysis results have been validated through the comparison of experimental. The experimental results measured directly by the strain gauge have given the confidence to FEA.

• Progress in Superconductivity and Cryogenics
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• v.3 no.2
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• pp.1-4
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• 2001

For the practical use of a superconducting wire to magnet application, it is important to assess the Young modulus and other mechanical properties of HTS tapes. In order to establish a test method of mechanical properties for oxide composite superconductors. tensile tests of Bi-2223 multi- filamentary tapes were carried out at room temperature, as an activity of the International round robin test proposed by the committee of VAMAS/TWA 16-Subrgroup. The tapes consisting of mutli-filamentary showed a three stage tensile behavior. At the initial stage of the stress-streain curve. The elastic deformation existed in a quite nattrow strain region. But the plastic deformation was observed in a wide strain region due to the platic flow of the Ag alloy matrix. The results of RRT were also reported and discussed.

• Structural Engineering and Mechanics
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• v.18 no.6
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• pp.769-790
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• 2004

The compressive behavior up to failure of short concrete members reinforced with fiber reinforced plastic (FRP) is investigated. Rectangular cross-sections are analysed by means of a simplified elastic model, able also to explain stress-concentration. The model allows one to evaluate the equivalent uniform confining pressure in ultimate conditions referred to the effective confined cross-section and to the effective stresses in FRP along the sides of section; consequently, it makes it possible to determine ultimate strain and the related bearing capacity of the confined member corresponding to FRP failure. The effect of local reinforcements constitute by single strips applied at corners before the continuous wrapping and the effect of round corners are also considered. Analytical results are compared to experimental values available in the literature.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.61-66
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• 2000

The fatigue crack initiation life is studied on automotive spot weldment made from cold rolled carbon steel(SPC) sheet by using DCPDM and local strain approach. It can be found that the fatigue crack initiation behavior in spot weldment can be definitely detected by DCPDM system. The local stresses and strains are estimated by elastic-plastic FEM analysis and the alternative approximate method based on Neuber's rule were applied to predict the fatigue life of spot weldment. A satisfactory correlation between the predicted life and experimental life can be found in spot weldment within a factor of 4.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.344-349
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• 2008

Ratcheting behavior of IN 718 was investigated at $649^{\circ}C$ under various proportional and non-proportional loading conditions with stress control. The material response was initially elastic but substantial plastic strain was developed as the material softened cyclically. Ratcheting strain was measured to near fatigue life, and is found to have three stages of development - primary, secondary (steady-state) and tertiary. The secondary stage dominates for most cases. Under the same equivalent stress amplitude and mean stress, it was revealed that circular path loading gives higher ratcheting rates and shorter lives than linear paths and that the more ratcheting occurs when the cyclic load is in the same direction as the mean stress. The ratcheting strain at failure depends not only on its rate but also on fatigue life itself, and it is not a primary life-determining factor.