• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.81-86
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• 2001

The concrete bridge decks are in need of replacement and rehabilitation due to decreasing load carrying capacity. In this study, to propose a strengthening technique that improves usability and structural performance of the bridge deck and to propose an efficient strengthening design technique which satisfies both the strength End serviceability of the bridge deck, this paper shows the failure characteristics of the strengthened bridge decks and proposes an empirical yield criterion. Therefore, strengthening efficiency was proposed based on the experiment and yield line analysis result. The yield line theory which adopts the modified criteria of Johansen is considered to predict the ultimate strength about all strengthening material(Carbon Fiber Sheet, Carbon Fiber Rod, Grid Type Carbon Fiber).

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.121-128
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• 2005

This paper introduces a method of predicting the behavior of compacted soil with an unsaturated soil mechanics by considering the effect of suction as an increasing consolidation yield stress. Two kinds of experiments were conducted. One is a series of static compaction tests to monitor the suction, and the other is a series of compression tests on compacted soil without soaking. The results of our tests indicate that it is possible to derive the distribution of suction on compaction curves and to hypothesize the changes in void ratio in the compression tests that depends on the suction. In addition, a new method is proposed to estimate the consolidation yield stress of compacted soil with a simple chart including compaction curves.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.112-118
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• 2000

Densification behavior of mixed copper and tool steel powder under cold compaction was investigated. By mixing the yield functions proposed by Fleck et al. and by Gurson for pure powder in terms of volume fractions and contact numbers of Cu powder new mixed yield functions were employed for densification of powder composites under cold compaction. The constitutive equations were implemented into a finite element program (ABAQUS) to compare with experimental data for densificatiojn of mixed powder under cold isostatic pressing and cold die compaction. finite element calculations by using the yield functions mixed by contact numbers of Cu powder agreed better with experimental data than those by volume fractions of Cu powder.

• Transactions of Materials Processing
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• v.19 no.7
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• pp.393-398
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• 2010

This paper investigates the effect of material properties on the formability of sheet metals based on the Marciniak-Kuczynski model (M-K model). The hardening behavior of the material is modeled as the Hollomon model with the strain rate effect. The yield surfaces are constructed with Hosford79 yield function. The material properties considered in this study include the R-value, the strain hardening exponent, the strain rate hardening exponent, and the crystal structure of the material. The effect of the crystal structure on formability is roughly expressed as the change of the yield surface by varying the value of the exponent in Hosford79 yield function. Results show that the R-value affects neither the magnitude nor the shape of right hand side of forming limit diagrams (FLDs). Higher strain hardening exponent and higher strain rate hardening exponent improve the formability of sheet metals because they stabilize the forming processes.

• Transactions of Materials Processing
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• v.25 no.3
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• pp.189-194
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• 2016

In the current study, spring-back of DP980 steel sheet was numerically evaluated for U-bending using a yield function with a hardening model. For spring-back prediction, two types of yield functions - Hill'48 and Yld2000-2d - were considered. Additionally, isotropic hardening and the Yoshida-Uemori model were used to investigate the spring-back behavior. The parameters for each model were obtained from uniaxial tension, uniaxial tension-compression, uniaxial tension-unloading and hydraulic bulging tests. The numerical simulations were performed using the commercial software, PAM-STAMP 2G. The results were compared with experimental data from a U-bending process.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.809-814
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• 1998

Recently many cases that using strengthening method with a steel plate or carbon-fiber sheet in a construction field are increasing. In this reason, it is demanded that developing a plan of preventing delamination of strengthening material. So in this research, for the case of strengthening method of steel plate, it is made use of notch and anchor bolt and for the case of carbon fiber sheet, it is made use of notch, anchor bolt, line anchor and shear strengthening. After all the cases were applied, we made 15 specimen beams. The beams was measured and analyzed about the behavior property of strengthened beams, the ability strengthening method, the relation between load and the shape of failure, the crack load, the yield load, the shape of crack pattern, the increasing rate from yield load and maximum load and the strain of rebar. All the strengthening methods results in almost same value until the yield load, and it wasn't quite different from the theoretical value. But for the case of increasing rate from the yield load and maximum load, comparing with the existing method, the new strengthening methods are proved to be profitable about the safety.

• Journal of the Korean Home Economics Association
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• v.26 no.3
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• pp.93-102
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• 1988

Rheological properties of cowpea and mung bean starch gels and pastes were investigated and compared with Instron Universal Testing machine and Brabender Viscometer. As the result of puncture test of gels, yield point force of mung bean starch gel was higher than that of cowpea starch gel. Compression coefficient of cowpea starch gel calculated by Bourne's equation was lower than that of mung bean starch gel. the stress relaxation test showed that viscoelastic properties of cowpea and mung bean starch gels may be represented by six element Maxwell model consisting of three Maxwell element in parallel. Cowpea and mung bean starch pastes showed bingham pseudoplastic behavior in 3, 5, 6, 7 and 8%. The consistency index in 7∼8% of cowpea starch paste were lower than those of mung bean starch paste. concentration dependence on consistency index and yield stress in mung bean starch were higher than those of cowpea starch. The yield stress of starch pastes was significantly correlated with yield point force by puncture test (r=0.996).

• Macromolecular Research
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• v.11 no.5
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• pp.387-392
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• 2003

The ablation effects of Ar-plasma treatment and alkali-decomposition behavior in NaOH solution of polyethylene terephthalate (PET) film were investigated. The modifications were evaluated by analysis of atomic force microscopy topographical changes, and by the measurement of decomposition yield in conjunction with heats of formation and electron densities of acyl carbon calculated by Parameterization Method 3 method. It has shown that the alkali-decomposition is hampered by plasma treatment and its decomposition yield is closely related with plasma treatment conditions such as exposure time to plasma. Plasma-treated PET films exhibited lower decomposition yield, compared to that of virgin PET. Increasing plasma exposure time contributes positively to decrease the decomposition yield. It has also shown that the topography of PET surface was affected by the base-promoted hydrolysis as well as Ar-plasma treatments. These behaviors are attributed to the decreased nucleophilicity of acyl carbon damaged by the ablation of Ar-plasma.

• Research in Community and Public Health Nursing
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• v.9 no.1
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• pp.117-127
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• 1998

The Theory of Planned Behavior has been shown to yield great explanatory power in health behavior as well as social behavior. This study was conducted to test the Theory of Planned Behavior in the prediction and intention of smoking cessation behavior in university student smokers. We conveniently sampled 204 university student smokers and investigated using questionaries, analyzing the data with the Pearson product-moment correlation, and multiple regression. The results are as follows : 1. There are significant correlations in direct and indirect measures of attitude toward smoking cessation behavior, subjective norm, and perceived behavioral control. 2. Behavior belief is significant in predicting attitudes toward smoking cessation behavior. Normative belief is significant in predicting the subjective norm. Control belief is significant in predicting perceived behavioral control. 3. Attitude toward smoking cessation behavior, subjective norm are significant in predicting intention of smoking cessation behavior. In conclusion, this study demonstrated strong support for the Theory of the Planned Behavior and its use to predict smoking cessation behavior in university students smokers. But, as perceived behavioral control is not significant in predicting smoking cessation behavior, indepth research is needed to evaluate the usefullness of the Theory of Planned Behavior and Reasoned Action Theory.

• International Journal of Concrete Structures and Materials
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• v.2 no.1
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• pp.57-62
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• 2008

When the yield line theory is used to estimate the ultimate strength of a concrete barrier, it is of primary importance that the correct assumption is made for the failure mode of the barrier. In this study, a static test was performed on two full-scale concrete barrier specimens of Korean standard shape that simulate the actual behavior of a longitudinally continuous barrier. This was conducted in order to verify the failure mode presented in the AASHTO LRFD specification. The resulting shape of the yield lines differed from that presented in AASHTO when subjected to an equivalent crash load. Furthermore, the ultimate strengths of the specimens were lower than the theoretical prediction. The main causes of these differences can be attributed to the characteristics of the barrier shape and to a number of limitations associated with the classical yield line theory. Therefore, a revised failure mode with corresponding prediction equations of the strength were proposed based on the yield lines observed in the test. As a result, a strength that was more comparable to that of the test could be obtained. The proposed procedure can be used to establish more realistic test levels for barriers that have a similar shape.