• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.431-438
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• 2005

In this paper, the characteristics of excessive horizontal stress components in Korea were studied using the in-situ hydraulic fracturing stress measurement data over five hundred in 110 individual test boreholes. Based on the in-situ testing data, the magnitude and orientation of the horizontal stress component and variation of stress ratio (K) with depth were investigated. And also horizontal stress magnitude versus depth relationships and distribution limits of stress ratio components were suggested. For the subsurface space above 310 m depth in the entire territory, the stress ratio has a tendency to diminish and be stabilized with depth, but for some areas, it was revealed that the excessive horizontal stress fields with stress ratio close to 3.0 below 200 m in depth have formed. The result of investigation for excessive horizontal stress regions indicates that there exist several regions above 300 m in depth where localized excessive horizontal stresses enough to induce potentially brittle failure around future openings have formed.

• Journal of Welding and Joining
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• 제32권5호
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• pp.32-43
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• 2014

Welding and joining technology has become a core field. Therefore it is more widely applied to nonferrous metals, inorganic and polymeric materials. That is because the high performance, high function and diversification trend of materials used as industrial technology develops. In the laser welding process, STS 304 and SCP1-S were used as the base materials, the output density was fixed $7MW/cm^2$, the protective gas was argon(Ar) and the transfer rate was fixed 5 mm/sec. and it was progressed while the magnetic field is gradually increasing by 100 mT ranging 0 to 400 mT. The tensile test showed in average about 6 % tensile strength improvement in the case of the laser welding process using the magnetic fields. In the shielded metal arc welding process using SPHC only or the combination of SPHC+STS304 as base materials. The electric current was set at 80 Amperes and the protective gas used argon(Ar) the same as the laser welding process and the strength of magnetic fields. In the shielded metal arc welding process using the magnetic fields, the tensile tests showed about 5 % tensile strength improvement in the case of using SPHC only, 3 % tensile strength improvement in the case of using the combination of SPHC+ STS304. In comparing the results of numerical analysis to the results of experimental tests, it was revealed that the temperature, thermal stress distribution and the behavior of molten pool were similar to those of real tests. Consequently, it may be considered that the numerical assumption and the analytical model used in this study were reasonable.

• 농촌계획
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• 제21권1호
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• pp.41-50
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• 2015

In this study, the relative importance for the perception of managers on the comprehensive rural village development projects was evaluated using the AHP method. The fields for evaluation were 4 fields including human relationships, working conditions, work compensation and work burnout. Also, the relative importance for the perception of managers and priority order were analyzed through 15 evaluation items. The analysis result shows that the human relationships among 4 fields were regarded as the most important field, followed by work compensation, working conditions and work burnout. Also, the relationship with the chairperson for the human relationships, continuity of employment for the working conditions, salary for work compensation, and mental stress for work burnout were considered respectively as the most important item. Also, salary among all evaluation items was considered as the most important item for the relative importance, followed by continuity of employment, relationship with village residents and mental stress. However, work load, consulting firms, impersonal treatment and the relations between the administration showed relatively low importance and priority order. It is considered that this analysis result will be used as important preliminary data for establishing the role of manager in the comprehensive rural village development project.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.414-427
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• 2020

The finite element method is used to simulate the navigation of an ice-area bulk carrier in broken ice fields. The ice material is defined as elastic, and the simulations are accomplished at four model speeds and three ice concentrations. The movements of ice floes in the simulation are consistent with those in the model test, and the percentage deviation of the numerical ice resistance from the ice resistance in the model test can be controlled to be less than 15 %. The key characteristics of ice loads, including the average ice loads, extreme ice loads, and characteristic frequency, are analyzed thoroughly in a comprehensive manner. Moreover, the effects of sailing speed and ice concentration on the ice loads are analyzed. In particular, the stress distribution of ice floes is presented to help understand how model speed and concentration affect the ice loads. The "ice pressure" phenomenon is observed at 90 % ice concentration, and it is realistically reflected both in the time―and frequency―domain ice force curves.

• Journal of Welding and Joining
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• 제21권6호
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• pp.77-83
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• 2003

The finite element analysis was performed for the cracks existing in residual stress fields in order to investigate the effects of configuration of residual stress distribution to the fatigue crack opening behaviour. And the variation of stress distributions adjacent to the crack caused by uploading was examined. The finite element model with contact elements for the crack plane and plane stress elements for the base material and the analytical method based on the superposition principle to estimate crack opening behaviour and the stress distribution adjacent to the crack subjected to uploading were used. The results of the analysis showed that crack opening behaviors and variations of stress distribution caused by uploading were changed depending on the configuration of residual stress distribution. When the crack existed in the region of compressive residual stress and the configuration of compressive residual stress distribution were inclined, a partial crack opening just behind of a crack tip occurred during uploading. Based on the above results, it was clarified that the crack opening behaviour in the residual stress field could be predicted accurately by the finite element analysis using these analytical method and model.

• Tribology and Lubricants
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• 제14권2호
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• pp.1-9
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• 1998

The electrorheological (ER) behavior of suspensions in silicone oil of phosphated cellulose particles (average particle size 17.77 ${\mu}{\textrm}{m}$) was investigated at room temperature with electric fields up to 2.5 KV/mm. In this paper, for development of anhydrous ER suspensions using at wide temperature range, we would like to know fundamental understandings on the ER activity. As a first step, the anhydrous ER suspensions dispersed the phosphated cellulose particles were measured, and not only the electrical characteristics such as dielectric constant, current density and electrical conductivity but also the rheological properties on strength of electric field and quantity of dispersed phase were studied. From the experimental results, the anhydrous ER suspensions dispersed phosphated cellulose particles showed a stable current density and very high performance of ER effect $(\tau/\tau_0=1030)$ on the 2.5 KV/mm and the dynamic yield stress $(\tau_y)$ was in exponential proportion to the strength of electric fields.

• 대한기계학회논문집A
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• 제24권9호
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• pp.2292-2301
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• 2000

We propose an accurate and efficient estimation method of transverse shear stresses for analysis and design of laminated composite structures by 4-node quadrilateral degenerated shell elements. To get proper distributions of transverse shear stresses in each layer, we use 3-dimensional equilibrium equations instead of constitutive equations with shear correction factors which vary diversely according to the shapes of shell sections. Three dimensional equilibrium equations are integrated through the thickness direction with complete polynomial membrane stress fields, which are recovered by REP (Recovery by Equilibrium in Patches) recovery method. The 4-node quadrilateral degenerated shell element used in this paper has drilling degrees of freedom and shear stresses derived from assumed strain fields that are set up at natural coordinate systems. The numerical results demonstrate that the proposed estimation method attains reasonable accuracy and efficiency compared with other methods and FE analysis using 4-node degenerated shell elements.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.399-404
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• 1999

Electro-rheological(ER) fluids are suspensions which show an abrupt increase in rheological properties under electric fields. The rheological response is very rapid and reversible when the electric field is imposed and/or removed. Therefore, there are many practical applications using the ER fluids. The purpose of the present study is to examine the flow characteristics of electro-rheological fluids. The field-dependent yield stress are obtained from experimental investigation on the Bingham property of the ER fluid. Then the steady relationshup between pressure drop and flow rate of the ERF was two fixed parallel-plates was measured under application of an electric fields. The electrical and rheological properties of zeolite based electro-rheological fluids were reported.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.397-398
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• 2006

The advanced piezoelectric ceramic composite actuator, which is called LIPCA with the FRP and the optimization of the laminate configuration, was performed to maximize the stress transfer and the fiber bridging effect. This study evaluated the effect of variable electric fields on the PZT characteristic, laminate configuration and fatigue characteristics under the resonance frequency, which meant the largest performance range and the changes of its interlaminar phase were also evaluated by stages. In conclusions, Comparing with the fatigue lift of intact LIPCA, the fatigue life of LIPCA embedded by the artificial delamination was decreased up to 50%. The micro void growth and the coalescence of epoxy were actively made at the interlaminar phase subject to the large tensile stress.

• 한국정밀공학회지
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• 제22권2호
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• pp.120-125
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• 2005

Effect of transverse electric fields on fracture behavior in ferroelectric ceramics under purely electrical loading is investigated. It is shown that the shape and size of the domain switching zone depend strongly on the ratio of the transverse electric field to the coercive electric field as well as the direction of the applied electric field. Under small-scale conditions, the crack-tip mode I and II stress intensity factors induced by ferroelectric domain switching are numerically obtained. The crack kinking in ferroelectric ceramics is also discussed.