• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.178-179
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• 2022

This study evaluated the crack reduction characteristics of concrete by type of fiber reinforced concrete. As a result of the experiment, it was shown that the fluidity decreased due to the mixing of the fiber reinforcing material. The higher the amount of fiber reinforced material used, the higher the decrease in fluidity. It was confirmed that the tensile strength was improved by the mixing of the fiber reinforcing material. The selection of fiber reinforcement has a great influence on the crack reduction effect.

• Computers and Concrete
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• v.19 no.6
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• pp.737-744
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• 2017

Geopolymer Concrete is typically proportioned with activator solution leading to moderately high material cost. Such cost can be enduring in high value added applications especially when cost savings can be recognized in terms of reduction in size of the members. Proper material selection and mix proportioning can diminish the material cost. In the present investigation, a total of 27 mixes were arrived considering the mix parameters as liquid-binder ratio, slag content and sodium hydroxide concentration to study the mechanical properties of geopolymer concrete (GPC) mixes such as compressive strength, split tensile strength and flexural strength. The derived statistical Response Surface Methodology is beleaguered to develop cost effective GPC mixes. The estimated responses are not likely to contrast in linear mode with selected variables; a plan was selected to enable the model of any response in a quadratic manner. The results reveals that a fair correlation between the experimental and the predicted strengths.

• Journal of the Earthquake Engineering Society of Korea
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• v.21 no.4
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• pp.197-204
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• 2017

This paper aims to analyze the economic feasibility and investigate the possibility of elastic seismic design of wind-designed highrise concentrically braced frames considering change of mechanical properties of Korean steel under the strong wind and the low seismicity in Korea. To this end, first, highrise concentrically braced frames were designed considering strong wind load. And then, analyses of the economics of them were performed. The seismic performance evaluation of wind-designed highrise buildings was conducted using the response spectrum analysis procedure. Analysis results show that it is possible to save up to approximately 90% of the amount of steel on the 10% increase in steel strength without serviceability. However, with serviceability, the design sectional area of the steel with relatively high strength tends to increment considerably because of the lateral stiffness due to reduction of the inertia moment and so on. This point might apply to limitation of the steel with high tensile yield strength.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.119-122
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• 2003

This report describes the procedure of detailed design and structural test for the composite flexure which is a part of the hingeless hub system. First, stacking sequence design for composite flexure was done, and structural analysis by using NASTRAN was made to verify structural stability and safety. Using FPS installed at KIMM, composite flexure was laid up and cured using a autoclave. Before rotor ground test, the basic structural tests such as a bench test, tensile strength test and shear strength test, for flexure, were accomplished. Through replacing existing metal hub part with new fabricated composite flexure, improvement of aeroelastic stability and weight reduction were achieved. This result will be applied to composite rotor system design fur helicopter.

• Journal of Powder Materials
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• v.8 no.3
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• pp.168-173
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• 2001

The effect of grain refinement of the strength and ductility of metallic materials is investigated. A model in which a single phase material is considered as an effectively two-phase one is discussed. A distinctive feature of the model is that grain boundaries are treated as a separate phase deforming by a diffusion mechanism. Deformation of the grain interior phase is assumed to be carried by two concurrent mechanism. Deformation of the grain interior phase is assumed to be carried by two concurrent mechanisms: dislocation glide and mass transfer by diffusion. The model was exemplified by simulating uniaxial tensile deformation of Cu down to the nanometer grain size. The results confirm the observed strain hardening behaviour and a trend for reduction of ductility with decreasing grain size at room temperature.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1041-1042
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• 2006

High heat-resistant Al-Fe-V-Si and Al-Fe-V-Si-X rapidly solidified powder metallurgy (RS P/M) alloys have been developed under well-controlled high purity argon gas atmosphere. The $Al_{90.49}Fe_{6.45}V_{0.68}Si_{2.38}$ (at. %) RS P/M alloy exhibited high elevated-temperature strength exceeding 300 MPa and good ductility with elongation of 6 % at 573 K. Reduction of $H_2O$ partical pressure in P/M processing atmosphere led to improvement in mechanical properties of the powder-consolidated alloys under elevated-temperature service conditions. Ti addition to the Al-Fe-V-Si conduced to enhancement of the strength at room temperature. The tensile yeild strength and ultimate strenght were 545 MPa and 722 MPa, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.308-314
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• 1997

Shrinkage and creep are the fundamental properties of concrete. These long term deformations can be seen as bothersome(increased deflection) or can be seen as reduction of compressive stress of prestressed concrete. Steel fibers advance the mechanical properties of concrete:tensile strength, ductility, flexural strength, fracture toughness, and post-cracking resistance, etc...Silica fume is pozzolanic material which combines with hydrated lime to generate silicate materials which increase the compressive strength and reduce somewhat the creep of concrete. This paper is the result of the long-term deformation by silica fume and steel fibers with varying percentages.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.177-182
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• 2000

This paper predicted the equivalent stiffness of spatially reinforced composites (SRC) using the volume average of a fiber rod and matrix stiffness, and the strength of SRC using the stiffness reduction and the modified Tsai-Wu composite failure theory. Those equivalent engineering constants are used to analyze the mechanical behavior and the failure of SRC structures. Because the distribution of equivalent engineering constants is varying with the change in SRC shape, we made a program that predicts engineering constants of SRC. Both 3-D and 4-D SRC show the smallest tensile modulus and the largest shear modulus at the maximum rotated direction from each rod. Also the strength properties show the same tendency.

• Steel and Composite Structures
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• v.9 no.2
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• pp.173-189
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• 2009

This paper presents a study on the behavior and design of bolted stainless steel plates under in-plane tension. Using an experimentally validated finite element (FE) program strength of stainless steel bolted plates under tension is examined with an emphasis on plate bearing mode of failure. A numerical parametric study was carried out which includes examining the behavior of stainless steel plate models with various proportions, bolt locations and in two different material grades. The models were designed to fail particularly in bolt tear-out and material piling-up modes. In the numerical simulation of the models, non-linear stress-strain material behavior of stainless steel was considered by using expressions which represent the full range of strains up to the ultimate tensile strain. Using the results of the parametric study, the effect of variations in bolt positions, such as end and edge distance and bolt pitch distance on bearing resistance of stainless steel bolted plates under in-plane tension has been investigated. Finally, the results obtained are critically examined using design estimations of the currently available international design guidance.

• Journal of the Korean institute of surface engineering
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• v.36 no.4
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• pp.339-346
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• 2003

Stainless steel wire has been used in industry, dental and medical parts. Especially, it has been used widely for the dental orthodontic materials. The orthodontic wire requires good mechanical properties, such as elastic strength, combined with a high resistance to corrosion. To increase elastic strength and good corrosion resistance, drawing methods(one-step and two-step drawing) have been used and the electrochemical characteristics of drawed wire have been researched using potentiodynamic method in 0.9％NaCl and field emission scanning electron microscope. The one-step drawed wire showed the formation of rough surface. The hardness and tensile strength of two-step drawed wire increased. For the case of two-step drawed wire, the corrosion resistance and pitting potential increased compared with one-step drawed wire due to the drawing induced small surface roughness, such as scratch. The passivation and active current density decreased as the reduction in area for drawing increased.