• Journal of Korea Foundry Society
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• v.31 no.4
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• pp.198-204
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• 2011

The present study was aimed to investigate the dependence of fatigue property on microporosity variation of low-pressure die-cast (LPDC) A356 alloy. The fatigue property of A356 alloy was evaluated through high cycle fatigue test, and the microporosity-terms used were the fractographic porosity measured from SEM observation on fractured surface and the volumetric porosity obtained through the density measurement using Archimedes's principle. The number of cycles to failure of A356 alloys depends obviously upon the variation of fractographic porosity, and can describe in terms of the defect susceptibility which depends on the microporosity variation at a given value of stress amplitude. The modified Basquin's equation was suggested through the combination of microporosity variation and static maximum tensile stress to fatigue strength coefficient. Using modified Basquin's equation, it could suggest that the maximum values of fatigue strength coefficient and exponent achievable in defect-free condition of A356 alloy are 265 MPa, -0.07, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.10a
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• pp.113-116
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• 1990

This study is designed to analyze the variation of grading and shape of aggregate with the number of rotations of Los-Angeles abrasion machine, and is aimed to analyze the effect of slump and compressive strength of strength of concrete with the shape of coarse aggregate by the abrasion act.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1253-1254
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• 2011

• Proceedings of the Korea Concrete Institute Conference
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• 1992.04a
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• pp.19-22
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• 1992

Properties of concrete has effected on the dosage variation of AE superplasticizer agent, Therefore, this study is designed for analysis of concrete properies according to the dosage variation of AE superplasticizer agent , and is aimed to analyze the effect slump, air content, compressive strength, resistance of freezing-and-thawing and for presenting the reference data on the practical use.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.1
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• pp.72-85
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• 2001

A study for the structural strength evaluation on the doubler plate subjected to the biaxial in-plane compression has been performed through the systematic evaluation process. In order to estimate the proper static strength of doubler plate, elasto-plastic large deflection analysis is introduced including the contact effect between main plate and doubler. The characteristics of stiffness and strength variation are discussed based on their results. A1so, in order to compare the doubler structure with the original strength of main plate without doubler, a simple formula for the evaluation of the equivalent flat plate thickness is derived based on the additional series analysis of flat plate structure. Using this derived equation, the thickness change of a equivalent flat plate is analyzed according to the variation of various design parameters of doubler plate and some design guides are suggested in order to maintain the original strength of main plate without doubler reinforcement. Finally, correlation between derived equivalent flat plate formula and the developed buckling strength formulas by author et a1. is discovered and these relations are formulated for the future development of simple strength evaluation formula of doubler plate structure.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.4
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• pp.92-105
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• 2000

A study for the structural strength evaluation on the slender doubler plate has been performed through the systematic evaluation process. In order to estimate the proper static strength of doubler plate subjected to the longitudinal in-plane compression, elasto-plastic large deflection analysis is introduced including the contact effect between main plate and doubler. The characteristics of stiffness and strength variation are discussed based on their results. Also, in order to compare the doubler structure with the original strength of main plate without doubler, a simple formula for the evaluation of the equivalent flat plate thickness is derived based on the additional series analysis of flat plate structure. Using this derived equation, the thickness change of a equivalent flat plate is analyzed according to the variation of various design parameters of doubler plate and some design guides are suggested in order to maintain the original strength of main plate without doubler reinforcement. Finally, correlation between derived equivalent flat plate formula and the developed buckling strength formulas by author et al. is discovered and these relations are formulated for the future development of simple strength evaluation formula of doubler plate structure.

• Journal of computational fluids engineering
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• v.13 no.4
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• pp.39-44
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• 2008

Numerical simulations of laminar flow over a sphere are conducted to investigate the effect of the Reynolds number on the characteristics of vortex shedding. The Reynolds numbers considered are between 300 and 475, covering unsteady planar-symmetric and asymmetric flows. Results show that the unsteady planar-symmetric flow can be categorized into two different regimes: single-frequency regime and multiple-frequency regime. The former has a single frequency component due to periodic shedding of the vortices with the same strength in every shedding cycle, while the latter has multiple frequency components due to cycle-to-cycle variation in the strength of shed vortices with the shedding angle fixed. The multiple-frequency planar-symmetric flow, which is newly found in the present study, occurs at Re=330${\sim}$360 between the single-frequency planar-symmetric flow and the asymmetric flow. On the other hand, the asymmetric flow occurs at Re${\geq}$365, where the vortices shed from the sphere show variation both in strength and shedding angle unlike the planar-symmetric flow. Also, it is shown that the breaking of planar symmetry is closely related to the imbalance of vortical strength between a pair of streamwise vortices.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.147-152
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• 2002

Effect of lip shape on the hole flangeability of high strength steel sheets is investigated. Circular plates of various hole sizes are tested and the variation of lip length as well as the variation of thickness on the sectional views of the finished lip were studied. The conventional hole flanging process is limited to a certain limit hole diameter below which failure will ensue during the hole expansion. The intention of this work is to examine the effect of lip shape on the flangeability of TRIP steel and Ferrite-Bainite duplex steel and find out major parameters which can affect flanging shape of high strength hot rolled steels. Over the ranges of conditions investigated, the minimum hole diameter of F+B steel is better than TRIP steel. while, the lip-shape accuracy of TRIP steel is better than that of F+B steel. although the tensile strength and elongation of %P steel are superior than those of Ferrite-Bainite duplex steel, the flangeability is found to be not so strongly sensitive to the tensile properties but sensitive to displacement on the circumferential direction of hole edge.

• Geotechnical Engineering
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• v.4 no.4
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• pp.5-18
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• 1988

A series of CU triaxial compression tests were conducted to investigate the variation of -untrained shear strength of underconsolidated clay at different degrees of consolidation. The soil samples were artificially made by one-dimensional consolidation using soft Bangkok Clay. The test results showed that the undrained shear strength of clay parabolically increased convoking downward with increasing degrees of consolidation. However, all the measured shear strength were unanimously related to the effective stress. These experimental results were used in the numerical analysis. A finite element computer program was developed to investigate the stability of submarine .slope undergoing rapid deposition taking into account the variation in soil compressibility and permeability during the consolidation process. The relationships of degree of consolidation with time as a function of rate of deposition and angle of slope were established. A method of predicting the time of slope failure and the volume of moving mass of soil was also made.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.10a
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• pp.155-160
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• 1992

In this study , the size effect on diagonal shear failure of reinforced high strength concrete beams was investigated, For this purpose, ten singly reinforced high strength concrete beams without web reinforcement were tested for five different dimensions of effective depth which were varied from 67mm to 915mm. The compressive strength of concrete used in this study was 53.7 MPa. One type of reinforcing bar with nominal yield strength of 400 MPa was used. Test results were analyzed and compared with strength predicted by ACI code equation, Zutty's equation and Bazant &Kim's equation. As the results, ACI code equation was seriously unconservative for beams with d of 915mm. Bazant & Kim's equation predicted well the trend of test data. Within the scope of this study, there was no clear difference in size effect with variation of compressive strength of concrete.