• Journal of Welding and Joining
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• v.19 no.4
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• pp.413-422
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• 2001

In this study. two-dimensional heat flow and residual stress in arc brazing to join the pipe and plate structure were analyzed by using a commercialized FEM package. Advantages offered by arc brazing are that strong joints can be produced with lower heat input than that of previous gas metal arc welding and narrower heat affected zone can usually be obtained than that in the case of torch brazing. To investigate the effects of process variables and minimize the thermal effects on the structure, this study presents a method for analyzing the heat flow and residual stress in arc brazing process according to variables such as traveling speed, torch angle and position. The simulation results were compared with the experimental ones to verify the numerical analysis method. The experiments include the measurement of HAZ size from the section of joints and residual stresses by using strain gages named 'section method'. A comparatively good agreement between the results of numerical analysis and experimental ones could be obtained in both of the temperature distribution and residual stress of the brazed structure. Using the proposed numerical analysis method, the process parameters were evaluated to get proper arc brazing conditions.

• Geotechnical Engineering
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• v.12 no.1
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• pp.87-110
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• 1996

To simulate the three4imensional effect occurring near the tunnel face in a two -dimensional model, empirical load -dirtribution ratio concept is frequently used in tunnel design. In this paper, three -dimensional analysis is performed and its results are compared with those of two dimensional analysis'to investigate the applicability of the loadiistribution ratio concept. Especially, stress concentration near the tunnel face is investigated in depth. A parametric study is performed to investigate the effect of each factor on the load distribution ratio. The factors considered here include unsupported span length, initial stress, rock quality, tunnel size and the depth of tunnel location Moreover, the load -distribution ratios for the typical tunnel sections in Seoul Subway to be used in the tunnel design are suggested.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.3
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• pp.22-34
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• 1996

Regarding the plate bending process by line heating method, in this study a simplified numerical analysis is performed for a beam model to predict its residual deformation and stress distribution. Using the modified strip theory and beam finite element method, a PC-based simulation program is developed for a thermo-elastic-plastic beam. The plate bending problem can be approximately replaced by a beam model using distributed springs to account for the effect of adjacent strips. The spring constants are chosen as the best fit with experiments. In this paper, it is assumed that the temperature distribution is already given and the temperature-dependent material properties are considered. To verify the simulation program, the results using present numerical algorithm are compared with other published experimental results and similar numerical studies. The comparison shows good agreement. The present PC-based computer program also shows good efficiency in computing time.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.3
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• pp.19-24
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• 2001

The lead frame, which is principal material used in semiconductor packaging, is required to be microscopic in leads and pitches to cope with miniaturization, thin film, large scale integrated. In addition, it is indispensable to eliminate residual stress and burrs occurring at manufacturing lead frames This thesis applied electrolytic abrasion in order to remove burrs and residual stress created during the stamp process. Electrolytic abrasion removed the burrs on the surface of lead frame. Removal of residual stress highly depends on the types of electrolyte solution. In case of perchloric system, electrolytic abrasion removed 23% of residual stress. Through removal of burrs and reducing residual stress, the reliability of lead frame was substantially improved.

• Geotechnical Engineering
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• v.10 no.3
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• pp.97-110
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• 1994

Interaction between an unlined tunnel may cause a serious stability both the tunnel and the overlying and unli Red tunnel interaction meta study on the three dimensional bets a three dimensional elasto plastic the program, a wide range of blur puter analysis such as stress distr menu and tunnel deformation were footing and unlined tunnel. The yes traces the ultimate bearing capacity only on the tunnel size and location revealed is that an unlined tunnel under a square footing is subjected to three dimensional stress pattern along the tunnel axis, and that the magnitudes of stresses in the foundation soil and around tunnel perimeter are considerably smaller when loaded with a square than with a strip footings and the difference varies with the location and the type of stress. It is also revealed that the footing failure mechanism varies with the degree of footing and tunnel interaction.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.228-240
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• 1991

Many experimental data of fatigue crack propagation show that the fatigue crack propagation process is stochastic. Therefore, the study on the crack propagation must be based on the probabilistic approach. In the present paper, fatigue crack propagation process is assumed to be a discrete Markov process and the method is developed, which can evaluate the reliability of the structural component by using Markov chain model(Unit step B-model) suggested by Bogdanoff. In this method, leak failure, plastic collapse and brittle fracture of the critical component are taken as failure modes, and the effects of initial crack distribution, periodic and non-periodic inspection on the probability of failure are considered. In this method, an equivalent load value for random loading such as wave load is used to facilitate the analysis. Finally some calculations are carried out in order to show the usefulness and the applicability of this method. And then some remarks on this method are mentioned.

• Journal of Korea Society of Industrial Information Systems
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• v.7 no.1
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• pp.34-41
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• 2002

There m many noise sources in living environment. Especially, noise that happen in apartment or tenement house may make neighborhood serious troubles. Thus, the development of new materials to reduce and improve the living noises is required. During past decade, various methodologies have been developed and researched to reduce and improve the living noises. However, there are many problems to apply these methodologies to practical our environment. In this thesis, we develop the new artificial material supporting high porous materials and lower pressure density to improve the problem caused in the safety design and sound absorbing material. To prove the efficiency of the developed methodology, we compare our methodology with conventional methodologies and also suggest an alternative methodology to contribute quiet life environments.

• Geotechnical Engineering
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• v.8 no.3
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• pp.61-74
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• 1992

In order to provide fundamental data for the design of geotextile drains, the in-plane permeability coefficients were determined by tests and permeable cllaracteristics were investigated, mainly on domestic nonwoven and composite getextile products used for drainage purpose. The results obtained are as follows, The thickness, the in-plane permeability coefficient and the transmissivity with the in- crease of compressive stress are found to be remarkably decreased when the compressive stress is lass than about 10KN/m2. The inflane permeability of filament nonwovens are found to be lower than that of composites or staple-fiher nonwovens, and the compressibility of the geotextile shown to be larger for the polyester nonwovens than for the polypropylene nonwovens. The relation of compressive stress, q and compressibility, Cr is expressed as Cr=13.37 In q+23.28 and that of compressibility on the basis of 2KN /m2, Cr' and decrease ratio of in-plane permeability coefficient is followed Pr: 1.25Cr'

• Geotechnical Engineering
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• v.11 no.4
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• pp.87-98
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• 1995

Laboratory tests were performed on modeling of in situ remediation of contaminated soils by aqueous solution extraction, thus investigating the feasibility of in situ treatments of soil to promote desorption of organic hazardous wastes. The investigation was conducted using phenol, aniline, quinoline, and 2-napthol adsorbed onto a UH40 soil, and various aqueous solutions were used to desorb, or otherwise remove, these organic contaminants. Decontaminants consisted of deionized water as a reference, hydrogen peroxide, acidy, bases, and surfactants. In situ conditions were modeled in the laboratory by permeating potential extracting liquids through reconstituted, contaminated soil specimens under controlled hydraulic gradients and stress condition through flexible wall permeameter tests. Sodium hydroxide desorbed phenol effectively. Aniline was effectively descorbed by nonionic surfactant. Anionic surfactant remediated quinoline and 2-napthol.

• Geotechnical Engineering
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• v.13 no.1
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• pp.123-136
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• 1997

By applying the finite element theory which is capable of handling the geometrically altered structure in a successive manner, the linear relationship between incremental displacements and the magnitude of the initial stress field was derived. Based on this relationship, back analysis code having the capability of dealing multi-step excavation problem was built and verified With this back analysis code, the measurements of the incremental displacements in a particular excavation step make it possible to back-calculate the initial stress state. illustrative examples showed the applicability of this code to a practical problem.