• Journal of the Korean GEO-environmental Society
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• v.13 no.3
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• pp.85-90
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• 2012

This paper deals with the results for a numerical analysis of single piles and pile groups in multi-layers soil(granite soil-clay-granite soil) subjected to monotonous lateral loading using the ABAQUS finite element software. The investigated variables in this study include free head and embedded capped single pile, pile diameter (0.5m), pile length (10m), and pile groups. Numerical analyses were conducted by variation of spacing piles(s=3D, 4D, 5D) to compare the behaviour of single pile without cap and group pile. The $1{\times}3$ pile group(leading pile, middle pile, trail pile) was selected to investigate the individual pile and group lateral resistance, the distribution of the resistance among the piles. The analysis model of clay and the material of granite soil was modeled by using Druker-Prager constitutive relationship and existing treatise respectively. The pile was considered as a elastic circular concrete pile. As a result, the more pile space was extended, the value of P-multiplier is appeared to be less effective to leading pile. The lateral resistance of single-layer showed approximately 4-20% larger than the multi-layers.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.2
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• pp.193-200
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• 2011

A BOR(Boil-Off Rate) prediction model for the NO96 membrane-type LNG insulation containment filled with superlite powders during laden voyage is presented in this paper. Finite element model for the unsteady-state heat transfer analysis is constructed by considering the air and water conditions and by employing the homogenization method to simplify the complex insulation material composition. BOR is evaluated in terms of the total amount of heat invaded into LNGCC and its variation to the major variables is investigated by the parametric heat transfer analysis. Based upon the parametric results, a BOR prediction model which is in function of the LNG tank size, the insulation layer thickness and the powder thermal conductivity is derived. Through the verification experiment, the accuracy of the derived prediction model is justified such that the maximum relative difference is less than 1% when compared with the direct numerical estimation using the FEM analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.3
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• pp.227-235
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• 2012

The void distribution in concrete materials strongly affects its material properties. Therefore, the identification of spatial distribution of void is important to understand and estimate material behavior. To examine and quantify the void distribution inside lightweight aggregates, CT(computed tomography) image is used. 3D lightweight aggregate images are generated by stacking of cross-sectional images from CT. Spatial distribution of void of aggregate along the direction is visualized on the sphere using probability distribution function. Stiffness of lightweight aggregate for the directions is also examined. It is confirmed that direction-based probability distribution and stiffness from CT images are effective in characterizing void distributions of aggregates.

• Journal of Aerospace System Engineering
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• v.12 no.5
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• pp.1-7
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• 2018

In this study, we proposed a high frequency induction hardening analysis method based on electromagnetic-thermal co-simulation. In the high frequency induction heating analysis, the results of the finite element analysis (FEA) (considering the change of the material property and the cooling factor according to the temperature) and those of the high frequency induction hardening experiment (using the S45C specimen) were compared. The hardness of the S45C specimens was measured using the micro Vickers hardness test to determine the depth of hardening. The measurement results were then compared with the results of FEA. The result of high frequency induction heating analysis showed that the temperature was more than $750^{\circ}C$, which is the A2 transformation point of S45C, while the temperature during quenching was below $200^{\circ}C$. The results showed that the difference of the depth of hardening between the FEA and the experiment is 0.2mm.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.631-642
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• 2013

The standard CPT(Cone Penetration Test), which can be easily performed to investigate in-situ soil engineering properties, has been widely used. CPT are also widely being utilized in centrifuge model tests. In this study, a miniature cone with 10mm diameter was developed and its applicability in the centrifuge was evaluated. The developed miniature cone was equipped with a four degree-of-freedom in-flight robot. A series of cone penetration tests was performed under four centrifuge acceleration levels. As results, the cone resistances measured at the same confining stress within shallow penetration depth were affected by the centrifugal accelerations. The critical depth was proportional to the cone diameter and relative density. Cone resistances results below the critical depth and soil parameters obtained from the laboratory tests were compared with those by previously proposed empirical relations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.1
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• pp.1-11
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• 2008

Stiffness estimation of a shear building due to local damages is usually achieved though structural analysis based on the assumed material properties and idealized numerical modeling of structure. Conventional numerical modeling, however, frequently causes an inevitable error in the structural response and this makes it difficult to exactly predict the damage state in structure. To solve this problem, this paper introduces a damage detection technique for shear building using genetic algorithm. The introduced algorithm evaluates the damage in structure using a flexibility matrix since the flexibility matrix can exactly be obtained from the field test in spite of using a few lower dynamic modes of structure. The introduced algorithm is expected to be more effectively used in damage detection of structures rather than conventional method using the stiffness matrix. Moreover, even in cases when an accurate measurement of structural stiffness cannot be expected, the proposed technique makes it possible to estimate the absolute change in stiffness of the structure on the basis of genetic algorithm. The validity of the proposed technique is demonstrated though numerical analysis using OPENSEES.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.7
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• pp.2341-2348
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• 2010

In this paper, strain and stress on space frame are analyzed at racing car under crash loads. As the deformation is reduced to a minimum during crash and the vulnerable parts are grasped, the safety of driver is ensured. The vehicle frame is modelled with truss structure by inputting the material property of carbon steel on finite element analysis. The increase of impulse momentum is due to speed change at frontal collision. This influence effected on vehicle frame is also analyzed by ANSYS program. The deformation of the frame is studied by applying the crash loads at front, side and rear directions. Though the influence on the seat of driver is small at frontal and rear crash, the deformation due to impact is progressed into this seat. The safety of frame is enhanced by making up for these weak deformations and these results of simulation analysis can be applied to the production of the actual vehicle frame.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.1
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• pp.1-9
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• 2007

The performance of the small scale cyclone incinerate system (100kg/hr) to process the sewage sludge containing high moisture is evaluated. The incinerate system design is based on properties of the domestic sewage sludge. The combustion characteristics of the incinerate system is tested and analyzed with the various operation conditions of the moisture level, the sludge feed rate and the auxiliary fuel feed rate. The pressure loss of the whole system is appeared relatively small of 700mmAq under the normal operating condition and the temperature distribution of the incinerator internal combustion is maintained less than 1000C. Auxiliary fuel of 4.7 1/hr is required to incinerate 100kg sludge which include 87% moisture. Because the inside temperature of the incinerator is maintained less than $1000^{\circ}C$, it is predicted that the most NOx measured is produced not from the heat during the combustion process but from the oxidation of the N ingredient in the sludge. From the component analysis of ash, the organic matter is not entirely detected. Accordingly, it is estimated that the complete combustion has been accomplished in the incinerator.

• Tunnel and Underground Space
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• v.18 no.2
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• pp.134-148
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• 2008

The state of in situ stress is an important factor in considering the suitability of a site as a geological repository for nuclear waste. In this study, three-dimensional distinct numerical analysis was conducted to investigate the effect of deformation zones on the state of stress in the Oskarshamn area, which is one of two candidate sites in Sweden. A discontinuum numerical model was constructed by explicitly representing the numerous deformation zones identified from site investigation and far-field tectonic stress was applied in the constructed model. The numerical model successfully captured the variation of measured stress often observed in the rock mass containing large-scale fractures, which shows that numerical analysis can be an effective tool in improving the understanding of the state of stresses. Discrepancies between measured and modelled stress are attributed to the inconsistent quality of measured stress, uncertainty in geological geometry. and input data for fractures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.11
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• pp.889-897
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• 2014

This paper presents a method for finding an optimized result by using a genetic algorithm (GA) based on a PEMFC analysis result. The conventional analysis method designs fuel cells one-by-one, and each result is compared to obtain the best performance. Because the computational burden of the conventional analysis is enormous, the present optimization process provides an inefficient tool by automatically setting the boundary and material properties and mesh generation. As the change can be reflected automatically in the channel geometry with GA, the fuel cell analysis result with various sizes can be obtained easily. Therefore, the global maximum performance can be obtained through a GA optimization procedure.