• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.03b
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• pp.55-61
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• 1996

Finite element calculations are performed for crystalline solids subjected to plane strain tensile loading. Using Asaro's double slop model, shearband developments in single crystals are analyzed. The effect of various rate sensitivities and latent hardening parameters on microscopic plastic behavior was clarified. Moreover the deformation behavior of polycystals which have grain boundaries was compared to that of single crystals.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.254-257
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• 2007

In this paper, anisotropic tensile properties of the AZ31B Mg-alloy sheet are obtained with the tensile test at elevated temperatures. Change of microscopic structures and the hardness is inspected after the solution heat treatment process in order to confirm the micro-structural stability of the used sheet metal. Results obtained from tensile tests show that it is very difficult to apply the conventional modeling scheme with the assumption of strain hardening to the forming analysis of the magnesium alloy sheet which shows the strain-softening behavior at the elevated temperature.

• Composites Research
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• v.26 no.4
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• pp.218-222
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• 2013

This study demonstrated that a slag, an industrial solid waste, can be used as a structural reinforcement. The mechanical properties(tensile strength and Elastic modulus) of slag reinforced composite(SRC) was investigated as functions of slag particle size (8~12 ${\mu}m$ and 12~16 ${\mu}m$) and volume fraction (0-40 vol.%). In order to investigate the interface and a degree of particle dispersion which have an effect on mechanical properties, optical microscopic images were taken. The results of tensile tests showed that the tensile strength decreased with an increase in slag volume fraction and particle size. The elastic modulus increased with an increase in slag volume fraction and particle size except for 30 vol.% SRC. The tensile strength decreased with an increase in slag particle size. The microscopic picture showed SRC has fine degree of particle dispersion at low slag volume fraction. SRC has a good interface at every volume fraction. However particle cluster was incorporated with an increase in slag volume fraction.

• Computers and Concrete
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• v.18 no.1
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• pp.39-51
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• 2016

This paper considers the tensile strength of concrete samples in direct, CTT, modified tension, splitting and ring tests using both of the experimental tests and numerical simulation (particle flow code 2D). It determined that which one of indirect tensile strength is close to direct tensile strength. Initially calibration of PFC was undertaken with respect to the data obtained from Brazilian laboratory tests to ensure the conformity of the simulated numerical models response. Furthermore, validation of the simulated models in four introduced tests was also cross checked with the results from experimental tests. By using numerical testing, the failure process was visually observed and failure patterns were watched to be reasonable in accordance with experimental results. Discrete element simulations demonstrated that the macro fractures in models are caused by microscopic tensile breakages on large numbers of bonded discs. Tensile strength of concrete in direct test was less than other tests results. Tensile strength resulted from modified tension test was close to direct test results. So modified tension test can be a proper test for determination of tensile strength of concrete in absence of direct test. Other advantages shown by modified tension tests are: (1) sample preparation is easy and (2) the use of a simple conventional compression press controlled by displacement compared with complicate device in other tests.

• International Journal of Korean Welding Society
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• v.3 no.1
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• pp.23-28
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• 2003

The effect of the welding speeds on the weld bead shape, microstructure, and mechanical properties in type 304 austenitic stainless steels was investigated by microscopic test, Erichsen test and tensile test. In this study welds were produced using autogeneous Direct Current Straight Polarity (DCSP) and pulsed current GTA welding. This study shows the ferrite content, ductility, tensile strength and elongation of high speed welds are decreased with increasing welding speed. The high speed welds exhibits satisfactory tensile strength, though the ductility is not good as that of the base metal.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.217-221
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• 2000

Nonlinear stress analysis of nuclear containment building wall element is carried out using microscopic material model. The present study mainly focuses on the finite element analysis of the nuclear containment building wall element under biaxial tensile stresses and it evaluates the perfomance of adopted microscopic material model in the membrane energy dominant situation. From the numerical analysis, the adopted material model peforms well and has a good agreement with experiment result. Finally, the result of present study can be severed as a benchmark test when concrete material model is in need of evaluation.

• Explosives and Blasting
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• v.31 no.2
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• pp.6-13
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• 2013

Recently, complaints or environmental problems caused by the noise and dust generated from crusher of the mine and quarry are emerging. Therefore mining facilities such as crushers and mills have been installed in an underground. In order to facilitate crusher equipments in the underground, excavation of large space is required and then the stability of the large space underground structure is an important issue. In this study, the blast experiments, which use a block of the limestone, are performed. Based on the blast experiments, the numerical model was prepared and simulated using dynamic fracture process analysis code(DFPA) with considering the rising time of applied borehole pressure and microscopic tensile strength variation. Comparing the non-dimensional crack length and no-dimensional tensile strength obtained from blast experiments and numerical analyses, the input parameters of DFPA code for predicting a radial tensile crack in limestone blasting were determined.

• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.655-664
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• 2007

The inherent characteristic of concrete tensile cracks, directional nonlocal crack damage, causes so-called rotating tensile crack damage and softening of compressive strength. In the present study, a plasticity model was developed to describe the behavior of reinforced concrete planar members In tension-compression. To describe the effect of directional nonlocal crack damage, the concept of microplane model was combined with the plasticity model. Unlike existing models, in the proposed model, softening of compressive strength as well as the tensile crack damage were defined by the directional nonlocal crack damage. Once a tensile cracking occurs, the microplanes of concrete are affected by the nonlocal crack damage. In the microplanes, microscopic tension and compression failure surfaces are calculated. By integrating the microscopic failure surfaces, the macroscopic failure surface is calculated. The proposed model was implemented to finite element analysis, and it was verified by comparisons with the results of existing shear panel tests.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.3
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• pp.127-133
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• 2003

The effect of chemical composition on the microstructural change and tensile property in TRIP-assisted steels with different chemical composition was investigated by using SEM, TEM, XRD and UTM. As a result of microscopic observation, the morphology of retained austenite could be identified as two types; a granular type in a steel containing higher Si and a film type in a steel having higher C. For the case of higher C-containing steel with a tensile strength of 860 MPa and a total elongation of 38%, film-typed retained austenite could be observed between lath bainitic ferrite. Actually, metastable retained austenite was a requisite for the good formability, which means that chemical composition plays a significant role in the microstructure and tensile property of TRIP-assisted steels. With respect to tensile property, the steels containing suitable Si and Mn, respectively, showed a typical TRIP effect in stress-strain curve, while a steel containing higher Mn content exhibited the similar behavior shown in dual phase steel.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.106-113
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• 2007

The effect of chemical composition on the microstructural change and tensile property in TRIP-assisted steels with different chemical composition was investigated by using SEM, TEM, XRD and UTM. As a result of microscopic observation, the morphology of retained austenite could be identified as two types : a granular type in a steel containing higher sillicon and a film type in a steel having higher carbon. For the case of higher carbon-containing steel with a tensile strength of 860 MPa and a total elongation of 38%, film-typed retained austenite could be observed between lath bainitic ferrite. Actually, metastable retained austenite was a requisite for the good formability, which means that chemical composition plays a significant role in the microstructure and tensile property of TRIP-assisted steels. With respect to tensile property, the steels containing suitable silicon and manganese, respectively, showed a typical TRIP effect in stress-strain curve, while a steel containing higher manganese content exhibited the assimilar behavior shown in dual phase steel.