• Transactions of Materials Processing
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• v.17 no.4
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• pp.292-301
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• 2008

Type 2 compressed natural gas(CNG) storage vessels for automobiles are becoming widely used. They are not only supplied to automakers in Korea, such as Hyundai Motors, but increasingly, they are being exported overseas. Autofrettage is a process that produces beneficial residual stresses in a vessel by subjecting it to excessive internal pressure. This strengthens the vessel and improves its fatigue resistance. This paper presents research investigating the autoftettage process and residual stresses it produces in type 2 CNG storage vessels. A finite element analysis technique and a closed form equation are used. Then, fatigue resistance is analyzed through a fatigue evaluation performed according to ASME section VIII.

• Geotechnical Engineering
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• v.2 no.3
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• pp.15-26
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• 1986

A great number of different pile-driving formulas are widely used to determine the load-carr-ying capacity during driving. However, engineers have been unable to agree on any particular pile.driving formula because the mechanisms of pile driving action which involves many complications such as hammer-pile-soil interaction could not be solved completely in any practical manner. This paper is presented for the purpose of giving field engineers a reliable analytical procedures for the prediction of pile.driving resistance without resort to electronic computers based on the theory of longitudinal wave transmission in conjunction with the wave equation and on the consideration of the effect of residual stresses induced by reversed friction in pile.

• Journal of Korean Association for Spatial Structures
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• v.19 no.3
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• pp.77-83
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• 2019

AU(A plus U-shaped) composite beam was developed for reducing the story height in the residential buildings, and saving the cosrtuction cost of floor structures. Structural performance and economic feasibility of the composite beam have been sufficiently approved through the structural experiments and the analytical studies. Fire safety for the practical application of the composite beam has also been verified through the fire resistance tests and the heat transfer analyses. In this study 2-points bending tests were performed on the four specimens already tested for fire resistance to evaluate the residual bending strength of AU composite beam after fire accident. The same bending test was performed on the one fresh specimen having the same section and span of the specimens for practically comparative study.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.3
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• pp.35-41
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• 2019

In this study, the fire resistance performance of polymer cement mortars which are used as a representative repair material for section restoration, is evaluated and residual bond strength is measured by considering unity with concrete. According to the evaluation of fire resistance performance of re-emulsification type polymer cement mortars, residual compressive strength was drastically decreased according to heating temperatures with an increase of polymer addition rate, and this seems to be attributable to the application of polymer film. In addition, an explosion phenomenon occurred frequently with an increase of addition rate, so this should be considered when selecting repair materials and processing.

• Journal of Sensor Science and Technology
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• v.4 no.4
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• pp.29-40
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• 1995

In this paper, the noise equivalent cicuits that is necessary to the formulation of D.C. and noise characteristics, residual component and input capacitance so as to analyze on the noise factors of the SIT is proposed. The simplest noise equivalent circuit is the model representing the mechanism of the SIT and the measured values in this model were found as small as the values of the shot-noise. In the source resistance inserted equivalent circuit is conformed that the shot-noise will be reduced by the negative-feedback effect of the source resistance. In oder to analyze the correct noise reduction factor, I proposed the equivalent circuit which the formulas of the source and drain resistance was induced. In the experiment which affirm the equivalent circuits, the influence of the signal source resistance and output load resistance on the residual component is small and the residual component can be expressed by the equivalent input noise resistance. Moreover, the input capacitance is 13.6 pF when the load resistance is $0{\Omega}$ and the capacitance which does not concern with the SIT operation directly, that is, gate wire etc, is 10pF or so.

• Geomechanics and Engineering
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• v.8 no.1
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• pp.53-66
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• 2015

Plastic wastes, particularly polyethylene terephthalate (PET) generated from used bottled water constitute a worldwide environmental issue. Reusing the PET waste for geotechnical applications not only reduces environmental burdens of handling the waste, but also improves inherent engineering properties of soil. This paper investigated factors affecting shear strength improvement of PET-mixed residual soil. Four variables were considered: (i) plastic content; (ii) plastic slenderness ratio; (iii) plastic size; and (iv) soil particle size. A series of unconfined compression tests were performed to determine the optimum configurations for promoting the shear strength improvement. The results showed that the optimum slenderness ratio and PET content for shear strength improvement were 1:3 and 1.5%, respectively. Large PET pieces (i.e., $1.0cm^2$) were favorable for fine-grained residual soil, while small PET pieces (i.e., $0.5cm^2$) were favorable for coarse-grained residual soil. Higher shear strength improvement was obtained for PET-mixed coarse-grained residual soil (148%) than fine-grained residual soils (117%). The orientation of plastic pieces in soil and frictional resistance developed between soil particles and PET surface are two important factors affecting the shear strength performance of PET-mixed soil.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.2
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• pp.94-101
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• 2010

Composite materials have a higher specific strength and modulus than traditional metallic materials. Additionally, these materials offer new design flexibilities, corrosion and wear resistance, low thermal conductivity and increased fatigue life. These, however, are susceptible to impact damage due to their lack of through-thickness reinforcement and it causes large drops in the load-carrying capacity of a structure. Therefore, the impact damage behavior and subsequently load-carrying capacity of impacted composite materials deserve careful investigation. In this study, the residual strength and impact characteristics of plain-woven CFRP composites with impact damage are investigated under axial tensile test. Impact test was performed using drop weight impact tester. And residual strength behavior by impact was evaluated using the caprino model. Also we evaluated behavior of residual strength by change of mass and size of impactor. Examined change of residual strength by impact energy change through this research and consider impactor diameter in caprino model.

• Corrosion Science and Technology
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• v.17 no.4
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• pp.176-182
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• 2018

Corrosion of the Cu alloy with 10wt% Ni in stagnant seawater with residual free chlorine was investigated. Despite that fact that Cu alloys are widely used for seawater applications due to their stubborn resistance to chloride attack, not much is known as to how the residual free chlorine in seawater affects corrosion of Cu and its alloys. In this work, immersion tests were conducted in the presence of different levels of chlorine for 90-10 Cu-Ni samples, one of the most frequently used Cu alloys for seawater application, mostly in shipbuilding. The results revealed no evidence for accelerated corrosion of the Cu-Ni alloy even in the presence of 5 ppm residual chlorine in seawater, signifying that the Cu-Ni alloy can be more tolerant to residual chlorine that has been commonly cited by the shipbuilding industry. However, comparison of polarization behavior of the alloy samples in the presence of different electrolytes with different concentrations of residual chlorine suggests that higher concentration of chlorine could increase the corrosion rate of the Cu-Ni alloy. Furthermore, it is suggested that microorganisms in the seawater could increase the corrosion rate of the Cu-Ni alloy by encouraging exfoliation of the corrosion product off the metal surface.

• Journal of Ocean Engineering and Technology
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• v.10 no.2
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• pp.106-119
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• 1996

The ceramic has various high mechanical properties such as heat, abrasion, corrosion resistance and high temperature strength compared with metal. It also has low speciffic weight, low thermal expansibillity, low thermal conductivity. However, it could not be used as structural material since it is brittle and difficult for the machining. Therefore, there have been many researches to attempt to join ceramic with metal which is full of ductillity in order to compensate the weakness of ceramic.The problem is that residual stress develops around the joint area while the ceramic/metal joint material is cooled from high joining temperature to room temperature due to remarkable difference of thermal expansion coefficients between ceramic and metal. Especially, the residual stress at both edges of the specimen reduces the strngth of joint to a large amount by forming a singular stress field. In this study, two dimensional finite element method is attempted for the thermal elastic analysis. The joint residual stress of ceramic/metal developed in the cooling process is investigated and the change of joint residual stress resulted from the repetitive heat cycle is also examined. In addition, it is attempted to clarify the joint stress distribution of the case of tensile load and of the case of superposition of residual stress and actual loading stress.

• Journal of the Korean Geotechnical Society
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• v.20 no.1
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• pp.75-82
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• 2004

To evaluate the characteristics of permeability in weathered residual soil, flexible wall permeameter tests are performed using undisturbed samples. The Influence of hydraulic gradient and confining pressure on the permeability of weathered residual soil is analyzed. To compare the characteristics of permeability between weathered soil and sand, similar tests are performed using Jumoonjin sand. Also, piping model tests are performed to investigate the piping resistance of weathered residual soil. As a result, weathered residual soil shows very dependable permeability on hydraulic gradient and very large resisting ability against piping compared with sand.