• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.419-433
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• 2009

Pressure grouting is a common technique in geotechnical engineering to increase the stiffness and strength of the ground mass and to fill boreholes or void space in a tunnel lining and so on. Recently, the pressure grouting has been applied to a soil-nailing system which is widely used to improve slope stability. The soil-nailing design has been empirically performed in most geotechnical applications because the interaction between pressurized grouting paste and the adjacent ground mass is complicated and difficult to analyze. The purpose of this study is to analyze the increase of pullout resistance induced by pressurized grouting with the aid of performing laboratory model tests and field tests. In this paper, two main causes of pullout resistance increases induced by pressurized grouting were verified: the increase of residual stress; and the increase of coefficient of pullout friction. From the laboratory tests, it was found that residual stress in borehole increases by pressurized grouting and dilatancy angle could be estimated by cavity expansion theory using the measured wall displacements. From the field test results, the pullout resistance of soil-nailing with pressurized grouting was found to be 10% larger than that of soil-nailing with gravitational grouting, mainly caused by mean normal stress increase and dilatancy effect. So, the pullout resistance could be estimated by considering these two effects. The radial displacement increases with dilatancy angle increase and the dilatancy angle decreases with injection pressure increase. The measured pullout resistance obtained from field tests is in good agreement with the estimated one from the cavity expansion theory.

• Journal of Institute of Convergence Technology
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• v.2 no.1
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• pp.38-42
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• 2012

A scroll compressor used in the air conditioning in automobile consists of the fixed scroll and the orbiting scroll. Temperature gradient in the scroll compressor during the operation induces the thermal expansion of two scrolls. Therefore, the gap between scrolls in the initial stage is regarded as an important variable in structural design of the scroll compressor. The coupled thermal-stress analysis was carried out for the scrolls of a scroll compressor. The temperatures of major points of two scrolls in the steady states were referred by the literature of C. Lin. The sequentially coupled thermal-stress analysis is utilized to the heat transfer analysis and the thermal expansion analysis. In the thermal expansion analysis, the contact analysis was considered between the fixed and the orbiting scrolls in order to obtain the penetration distance and the contact pressure between two scrolls. The range of deformation was from 44 to $76{\mu}m$ according to the height of the scroll. The maximum penetration distance of $60{\mu}m$ occurred at the top surface of the fixed scroll in the center of the scroll parts.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.6
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• pp.993-1000
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• 2002

The objective of this work is to develop the capability to analyze accurately the mixed-mode propagation of a crack in composite structures with elastic orthotropic material stiffness properties and anisotropic material strength characteristics. In order to develop the capability to fully analyze fracture growth and failure in anisotropic structures, we examined the fundamental problem of mixed mode fracture by carrying out the analysis on orthotropic materials with an inclined crack subject to biaxial loading. Our goal here is to include an additional term in the asymptotic expansion of the crack tip stress field and to show that the direction of crack initiation can be significantly affected by that term. We employ the normal stress ratio theory to predict the direction of crack extension. It is shown that the angle of crack extension can be altered by horizontal loads and the use of second order term in the series expansion is important f3r the accurate determination of crack growth direction.

• Computational Structural Engineering
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• v.8 no.1
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• pp.173-186
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• 1995

It is well known that structures constructed by bonding two or more materials and then subjected to temperature change experience thermal stress. This stress results from thermal expansion mismatch of materials. The present paper derives formulas for the stresses in a bimaterial axisymmetric disk which is subjected to a uniform temperature change. First, an approximate solution following strength-of-materials principles is developed. However, the strength-of-materials solution has difficulty in predicting both the peak value of interfacial stresses and its associated distribution. Next, a solution consistent with the theory of elasticity is developed by way of an eigenfunction expansion approach. The eigenfunction analysis is compared with finite element stress analysis results for a specific numerical example. Finite element analysis results show that the interfacial stresses are adequately predicted by eigenfunction solution. Therefore, the method developed in this paper will be useful in determination of the interfacial stress state.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.99-100
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• 2006

Cold gas dynamic spray or cold-spray is a deposition process, which causes deformation of a thin substrate. The deformation is usually convex to the deposited side. In this research, the main cause of the deformation was investigated using 6061-T6 aluminum alloy. The effects or anisotropic coefficient or thermal expansion (CTE) or the deposited layer by cold-spray and residual stress were studied by experiments and finite element analysis. The Hole Drilling method was applied to measure residual stress in the cold-spray layer and substrate. The data obtained by the experiments were used for the analysis of substrate deformation. From the result of the analysis, it was concluded that compressive residual stress was the main reason of substrate deformation while CTE had little effect.

• Journal of Biosystems Engineering
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• v.9 no.2
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• pp.89-96
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• 1984

This study was intended to search the thermal properties of rice which are necessary in preventing qualitative and quantitative losses in the drying and milling processes. First, the coefficient of cubical thermal expansion of brown rice was measured, which is required for analyzing the internal stress of rice, and then theoretical thermal and moisture stresses were calculated. The results are summarized as follows: 1. The coefficient of cubical thermal expansion of brown rice was about $2.81{\times}10^{-4}/^{\circ}C$ in the temperature range of $10^{\circ}C-60^{\circ}C$. 2. When the shape of brown rice was assumed to be a sphere or a cylinder, maximum thermal stress due to temperature change of $20^{\circ}C-60^{\circ}C$ was in the range of $25-100kg/cm^2$. And maximum moisture stress was in the range of $450-650kg/cm^2$ when the drying temperature was $35^{\circ}C$, initial and final moisture contents of brown rice were 20% and 14% (w.b.), and the moisture diffusion coefficient was assumed to be $6.79{\times}10^{-4}cm^2/hr$. 3. Consequently, it was concluded that crack formation in a rice kernel is mainly caused by moisture stress.

• International Journal of Highway Engineering
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• v.17 no.2
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• pp.13-20
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• 2015

PURPOSES: This paper describes the expansion caused by the alkali-aggregate reaction (AAR) in concrete pavement currently in service. It also discusses the effects of joints installed to release the stress induced by the AAR expansion. METHODS: The expansion effect on concrete pavement was verified by a visual inspection and long-term measurement of the joint width of a cut-section. The behaviors of 16 newly installed joints were monitored as part of the investigation and long-term monitoring was carried out for three years after cutting. RESULTS: The behavior of a bridge was affected when AAR occurred in the connected pavement. The newly installed joints shrank in the longitudinal direction of the bridge after cutting. The width of the joints decreased over the six months after cutting. A large portion of the joint width (8.5cm) was found to have closed nine months after cutting. It had ultimately shrunk by about 92 percent when the final measurement was taken. CONCLUSIONS : The expansion of the pavement due to AAR was quantitatively described by visual inspection and the long-term monitoring of the newly cut joints. However, the width of the new joints decreased over the six to nine months after cutting. Additional research should be conducted to determine a means of controlling the expansion due to AAR in the pavement.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.2
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• pp.154-158
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• 2013

Expansion joint has been utilized in many areas including automotive bellows for exhaust system. Usage of expansion joint has been increased due to its inherent flexibility and excellent anti-vibration property. Simple shape of expansion joint is modeled to understand the behavior of joint system. 27 design cases using 3 design factors with 3 levels are constructed by design of experiment. Each case is simulated to find the most influential design factors. Response for this study, maximum stress in the expansion joint, has been used to determine main design factors of joint. Among the 3 design factors, factor B has affected greatly a response in the formation of optimum shape of joint. Also, interaction factor, $A{\times}B$, has also showed its influence to the response of joint. This study showed that design of experiment combined with finite element analysis could be used in the design decision process effectively in the design of expansion joint.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.2
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• pp.133-144
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• 1996

To get accurate results, the realistic stress-strain relationships of soils are dependent on a number of factors such as soil types, density, stress levels and stress path. Such attempts are continuously being made by the developement of analytical models for soils incorporating all such factors. Isotropic compression-expansion test and a series of drained conventional triaxial tests with several stress path for Baekma river sand were performed to investigate parameters characteristics of Lade's single work hardening model dependant on the stress path. Using the computer program based on the regression analysis, the values of parameters for the model were determined. In conclusion, the parameters of Lade's model are little influenced by the stress paths. Though yield criterion parameters ( h, ${\alpha}$a) are much influenced by stress level and stress path, the parameters don't have influence on stress-strain behavior.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.4
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• pp.443-447
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• 2004

In this study, we investigated the necessity of encapsulation layer to maximize flexibility of brittle indium-tin-oxide (ITO) on polymer substrates. And, Young's modulus (E) of encapsulation layer han a significant effect on external bending stress and the coefficient of thermal expansion (CTE) of that han a significant effect on internal thermal stress. To compare the magnitude of total mechanical stress including both bending stress and thermal stress, the mechanical stress of triple-layer structure (substrate / ITO / encapsulation layer or substrate / buffer layer / ITO) can be quantified and numerically analyzed through the farthest cracked island position. As a result, it should be noted that multi-layer structures with more elastic encapsulation material have small mechanical stress compared to that of buffer and encapsulation structure of large Young's modulus material when they were externally bent.