• The korean journal of orthodontics
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• v.25 no.3 s.50
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• pp.263-271
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• 1995

The purpose of this study nab to evlauate and compare the effect of the variable factors of wire on the elastic properties of looped rectangular wire. Five variable factors were presented-material(Hi-T, blue Elgiloy), wire size(.016'$\;\times\;$.022', .018'$\;\times\;$.025'), loop length(15mm, 20mm), loop configuration(open loop, closed loop), gabling (non-gable, gable). So, the total 256 specimens were divided into 32 groups, and each of those nab pulled on Instron testing machine. The load-deflection curve of each wire obtained, from which force, range in elastic limit, and stiffness were computed and analyzed statistically. The results were obtained as follows : 1. All of the variable factors - wire material, size, loop length loop configuration, and gabling - took a significant effect on load-deflection rate of looped wire. 2. The force at elastic limit was the smallest in the group of Hi-T, .016'$\;\times\;$.022', 20mm loop length, open loop, non-gable, and the largest in the group of blue Elgiloy, .018'$\;\times\;$.025', 15mm loop length, closed loop, non-gable. 3. The range at elastic limit was the smallest in the group of Hi-T, .018'$\;\times\;$.025', 15mm loop length, open loop, non-gable, and the largest in the group of HI-T, .016'$\;\times\;$.022', 20mm loop length, closed loop, gable. 4. Loop configuration and loop length were the most effective factors on the elastic properties of looped wires, and gabling was the least effective.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.2
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• pp.227-234
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• 2010

To investigate the flexural behavior of RC beams strengthened with carbon fiber sheets, 1 control beam and 8 strengthened beams(4 NU-beams without U-shaped band and 4 U-beams with U-shaped band) are tested. The variables of experiment are composed of the number of carbon fiber sheets and the existence of U-shaped band, etc. The experimental results showed that the strengthening system with U-shaped band controls the premature debonding and provides a more ductile failure mode than the strengthening system without U-shaped band. It can be found from the load-deflection curves that as the number of fiber sheets is increased, the maximum strength and the flexural rigidity is increased. The experimental results are compared with the analytical results of nonlinear flexural behaviors for strengthened RC beam. The proposed analytical method for strengthened beams is proved to be accurate by an experimental investigation of load-deflection curve, yield load, maximum load, and flexural rigidities in the pre- and post-yielding stages.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.32-38
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• 2006

A clutch hydraulic system for automotive manual transmissions transfers hydraulic pressure generated by driver's pedal manipulation to the clutch mechanism. The foot effort when the clutch pedal is pushed is different than that when the clutch is returned. The effort or load difference, called hysteresis, is caused by the friction produced between rubber seal and inner wall inside the hydraulic cylinder. This clutch pedal travel foot effort hysteresis is essential for a clutch hydraulic system design and analysis. The dynamic model for a clutch hydraulic system is developed and a simulation analysis is performed to estimate the fiction coefficient as a function of the cylinder pressure. The simulation result is then compared to the measurements obtained from a clutch hydraulic system tester to ensure the reliability of the dynamic model and the coefficients estimated. Also the estimated friction coefficients at various pressure values are compared to those reported by an independent study.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.102-105
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• 2001

In this paper, the solution of two dimensional deflection of circular wavy elastica beam was obtained for one end clamped boundary and concentrated load condition. The beam was regarded as a linear elastic material. Wavy shape was described as a combination of half-circular arc smoothly connected each other with constant curvature of all the same magnitude and alternative sign. Also load direction was taken into account. As a result, the solution was expressed in terms of a series of integral equations. While we found the exact solutions and expressed them in terms of elliptic integrals, the recursive ignition formulae about the displacement and arc length at each segment of circular section were obtained. Algorithm of determining unknown parameters was established and the profile curve of deflected beam was shown compared with initial shape.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1181-1184
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• 2001

This study was performed FEM analysis of RC beams strengthened with CPS, in order to verify the effect strengthened of the loading situation. By load-deflection curve, It was not different that max capacity of RF2-L0 strengthened with CFS on the sound and RF2-L60 strengthened with on the 60% loading situation of service load. When RC beam was shortly strengthened with CFS, bond element of beam on the end was ripped off. Because stress was concentrated on bond element of beam on the end.

• Structural Engineering and Mechanics
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• v.41 no.4
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• pp.441-458
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• 2012

The shear strength is an important factor in the design of prestressed concrete beams. Therefore, researchers have utilized various methods to determine the shear strength of these elements for the design purposes. To evaluate some of the proposed theoretical methods, numerous models of post-tensioned beams with or without vertical prestressing are selected and analyzed using the finite element method and assuming nonlinear behavior for the materials. In this regard the validity of modeling is evaluated based on some tests results. In the second part of the study two beam specimens are built and tested and their load-deformation curve and cracking pattern are studied. The analytical results consist of compressive strut slope and mid span load deflection are compared with some experimental results, and the results of some codes' formulas. Finally comparing the results of nonlinear analysis with the experimental values, a new formula is proposed for determining strut slopes in prestressed concrete beams.

• Journal of Korea Foundry Society
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• v.2 no.2
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• pp.2-9
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• 1982

This paper is concerned with the improvement of impact and tensile Properties of spheroidal graphite cast iron of the following duplex matricess which were heat treated in the eutectic transformation temperature range (that is, $({\alpha}+{\gamma})$ coexisting range) ; ferrite-martensite, ferrite-bainite and ferrite-pearlite. The absorbed energy and maximum load was measured by recording the load-deflection curve with instrumented Charpy impact testing machine in the temperature range from $+100^{\circ}C$ to $-196^{\circ}C$. It was found the ferrite-bainite duplex matrix showed the highest toughness among the above matrices in the room temperature and the low temperature range. Comparison of this matrix to ferrite-pearlite matrix(that is, as cast) showed a lowering of $27^{\circ}C$ in the nil-ductility transition temperature (NDT) and a lowering of $40^{\circ}C$ in the ductile-brittle transition temperature (TrE), Which seems to result from the finner dimple pattern observed using miorofractography.

• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.163-172
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• 2003

As concrete structures are getting larger, higher, longer, and specialized, it is more required to develop steel fiber concrete and apply to the real world. In this research, it is aimed to have fatigue strength examined, varying the steel fiber content by 0%, 0.75%, 1.00%, 1.25%, by experimental study of Two-spans Beam with Steel Fibrous with repeated loads. The ultimate load and the initial load of flexural cracking were measured by static test. In addition, the load versus strain relation, load versus strain relation, load versus deflection relation, crack pattern and fracture mode by increasing weight was observed. On the other hand, the crack propagation and the modes of fracture according to cycle number and the relation of cycle loading to deflection relation and strain relation was observed by fatigue test. As the result of fatigue test, Two-spans Beam without Steel Fibrous was failed at 60~70% of the static ultimate strength and it could be concluded that fatigue strength to two million cycle was around 67.2% by S-N curve. On the other hand, that with Steel Fibrous was failed at 65~85% of the static ultimate strength and it could be concluded fatigue strength to two million cycle around 71.7%.

• KIEAE Journal
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• v.8 no.5
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• pp.61-68
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• 2008

For the recycling of the resources and the preservation of the environment, this study's purpose is to measure flexural behavior of the reinforced concrete beams with the major variables like concrete strength, replacement ratio of the recycled aggregate and the waste foundry sand and the tension reinforcement ratio and to present the data of the recycled aggregate used for the structure design. The experiment on the flexural behavior resulted in the followings. The ultimate strength of recycled R/C beam was manipulated proportionate to the tension reinforcement ratio, however the strength instantly decreased after passing the ultimate load due to the destroyed concrete of the compression side. The deflection at the maximum load varied from the tension reinforcement ratio by 5.5 times. The test specimen with the tension reinforcement ratio less than $0.5{\rho}b$ showed constant curve without change in the load from the yield to the ultimate load in contrast to the distinctive plastic region where the displacement was rising. Although the strain of main tension steel with the reinforcement ratio indicate different, the design of recycled concrete member can be applied for current design code for reinforced concrete structure as the ratio of tension reinforcement district the under the reinforcement ration in a balanced strain condition.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.79-86
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• 2005

This paper deals with the static optimal shapes of simple beams which are subjected to a vertical point load. The area and second moment of inertia of the regular polygon cross-section of the tapered beams are determined, which have always same volume and same length for the parabolic taper. The differential equation governing the elastic curve is derived using the small deflection theory and solved numerically. By using the numerical results of deflections, rotations and bending stresses of such beams, the optimal shapes, namely, optimal section ratios, of the beams subjected to a single point load according to variation of load position parameters are determined and presented in the figures. Examples of the static optimal shapes for beams with a single load and multiple loads are reported. The design process of this study can be used directly for the minimum weight design of simple beams.