• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.2
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• pp.64-72
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• 1995

A series of cubical triaxial tests with three independent principal stresses was per- formed on Baekma river sand( # 40~100). It was found that the major principal strain at failure remained approximately constant for b values larger than about 0.3 for both the drained and undrained condition, and thereafter increased as b value decreased. The test results showed that the direction of the strain increment at failure form acute angles with the failure surfaces for both the drained and undrained condition. The results were thus not in agreement with the normality condition from classic plasticity theory. Howev- er, it was found that the projections of the plastic strain increment vectors on the octahe- dral plane were perpendicular to the failure surface in that plane. Failure strength in terms of effective stress anlaysis was greatly influenced by the variation of intermediate principal stress and so was failure criterion. The effective stress failure surfaces for both the drained and undrained condition were estimated quite well by use of Lade's failure criterion.

• Transactions of Materials Processing
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• v.6 no.2
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• pp.118-135
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• 1997

In order to analyze the deformation and residual curvature of steel sheets in the strip processing lines, a program for calculating curvature and work hardening of sheet was developed. Strip deformation caused by repeated bending under tension in the process lines was analyzed on the basis of the incremental-plasticity theory with the mixed hardenting model for the purpose of predicting the strip shape and the yield stress change. The developed calculation program was applied to predict curl and gutter of sheets within a 10% difference. The yield stress increment was also predicted with the similar accuracy. Application of the model to tension legvelling process showed that gutter could be controlled by intermesh and elongation. The yield stress increment in the electro-galvanizing line calculated by the developed program was found to be dependent on the yield strength, the applied tension and the diameter of the smallest roll.

• Journal of the Korean institute of surface engineering
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• v.37 no.5
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• pp.273-278
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• 2004

The requirements of getting spring steel with higher fatigue strength have been increased to achieve the weight reduction of a vehicle. As the possible increment in fatigue strength by using the conventional shot peening treatment is found to be limited, it is necessary to modify the shot peening treatment. In this study, to investigate the effects of warm shot peening on increasing fatigue strength, tests are conducted on spring steel SAE9524. By the results of rotating bending fatigue tests, the fatigue strength increases up to 23.8% in warm shot peening specimens at $200^{\circ}C$ compared with conventional shot peening. The major reason why the warm shot peening is effective to the improvement of fatigue strength is the increment of the compressive residual stress, which can be effectively formed by shot peening under the condition of warm temperature than room temperature.

• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.91-108
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• 2000

Most of cervical abrasion and erosion lesions show gingival margin where the cavosurface angle is on cementum or dentin. Composite resin restoration of cervical lesion shrink toward enamel margin due to polymerization contraction. This shrinkage has clinical problem such as microleakage and secondary caries. Several methods to diminish contraction stress of composite resin restoration, such as modifying cavity form and building up restorations in several increments have been attempted. The purpose of this study was to compare polymerization contraction stress of composite resin in Class V cavity subjected to cavity forms and placement methods. In this study, finite element model of 5 types of Class V cavity was developed on computer tomogram of maxillary central incisor. The types are : 1) Box cavity 2) Box cavity with incisal bevel 3) V shape cavity 4) V shape cavity with incisal bevel 5) Saucer shape cavity. The placement methods are 1) Incisal first oblique incremental curing 2) Bulk curing. An FEM based program for light activated polymerization is not available. For simulation of curing dynamics, time dependent transient thermal conduction analysis was conducted on each cavity and each placement method. For simulation of polymerization shrinkage, thermal stress analysis was performed with each cavity and each placement method. The time-temperature dependent volume shrinkage rate, elastic modulus, and Poisson's ratio were determined in thermal conduction data. The results were as follows : 1. With all five Class V cavifies, the highest Von Mises stress at the composite-tooth interface occurred at gingival margin. 2. With box cavity, V shape cavity and saucer cavity, Von Mises stress at gingival margin of V shape cavity was lower than the others. And that of box cavity was lower than that of saucer cavity. 3. Preparing bevel at incisal cavosurface margin decreased the rate of stress development in early polymerization stage. 4. Preparing bevel at incisal cavosurface margin of V shape cavity increased the Von Mises stress at gingival margin, but decreased at incisal margin. 5. At incisal margin, stress development by bulk curing method was rapid at early stage. Stress development by first increment of incremental curing method was also rapid but lower than that by bulk curing method, however after second increment curing final stress was the same for two placement methods. 6. At gingival margin, stress development by incremental curing method was suddenly rapid at early stage of second increment curing, but final stress was the same for two placement methods.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.6
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• pp.77-87
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• 2012

Recently, Load and Resistance Factor Design (LRFD) based on reliability analysis has become a global trend for economical and rational design. In order to implement the LRFD, quantification of uncertainty for load and resistance should be done. The reliability of result relies on input variable, and therefore, it is important to obtain exact uncertainty properties of load and resistance. Since soil stress is the main reason causing the settlement or deformation of ground and load on the underground structure, it is essential to clarify the uncertainty of soil stress distribution for accurately predict the uncertainty of load in LRFD. In this study, laboratory model test on silty sand bed under probabilistic load is performed to observe propagation of upper load uncertainty. The results show that the coefficient of variation (COV) of soil stress are varied depending on location due to non-linear relationship between upper load increment and soil pressure increment. In addition, when the load uncertainty is transmitted through ground, COV is decreased by damping effect.

• Applied Chemistry for Engineering
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• v.5 no.6
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• pp.943-948
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• 1994

The properties of uncured rubber compound and swelling behavior of cured rubber compound with carbon black(N33O grade) increment. Bound Rubber content(BRC) increased according to carbon black increment and ${\alpha}_f$, behavior of uncured rubber compound filled with carbon black, was 1.46. Carbon black added to rubber compound showed behavior of spherical particle by bound rubber. The $C_1$ values of cured rubber compounds, which measured by the stress-strain method of Mooney-Rivlin, increased with carbon black increment.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.613-616
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• 1999

The bond between reinforcing bar and concrete is a significant factor to confirm that they behave uniformly in the reinforced concrete. Thus, the studies on this field have been conducted by many researchers. But for the high strength lightweight concrete few studies have been done. In this study, the steel fiber reinforced high strength lightweight concrete developed to complement the brittleness of the high strength lightweight concrete was studied experimentally to find the local bond stress. Total 20 specimens were tested and the measured test values were compared with those calculated according to ACI 318-95 code and CEB-FIP code, respectively. The results indicate that the maximum bond stress has been influenced by increment of volume fracture of steel fiber, compressive strength and cover, Especially steel fiber caused not only increment of bond strength but also ductile behaviro.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.1
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• pp.106-117
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• 1998

The nature of stress-path dependency, the principle that governs deformations in granular soil, and the use of Lade's double work-hardening model for predicting soil response for a variety of stress-paths have been investigated, and are examined The test results and the analyses presented show that under some conditions granular soils exhibit stress-path dependent behavior. For stress-paths involving unloading or reloading, the stress-path with the higher average stress level produces the larger strains, whereas all stress-paths having the same intial states of stress, and involving only primary loading conditions, produce strains of similar magnitudes. Experimental evidence indicates that the stress- path dependent response obtained from the double work-hardening model is also observed for real soils. It is concluded that the influence of stress history on the friction angle is negligible and the strains increment direction is uniquely determined from the state of stress but is not perpendicular to the yield surface. The strains calculated from Lade's double work-hardening model are in reasonable agreement with those measured.

• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.41-48
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• 2002

Anisotropy of stiffness, from extremely small strains to post-failure strains, of isotropically consolidated air-pluviated sands in plane strain compression was studied by using the newly developed instrumentation fur small strain measurements, Seven types of sand of world-wide origins were tested, which have been extensively used for research purposes. Stress-strain relationships for a wide range of strain from about 0.0001% to the peak were obtained by measuring axial and lateral strains locally free from the effects of bedding and membrane penetration errors at the specimen boundaries. The result showed that the relationship between the principal stress ratio and the principal strain increment ratio was constant, being rarely affected by the over-consolidation ratio and the confining pressure. Although in the small strain the anisotropy hardly affected the relationship between the principal stress ratio and the principal strain increment ratio, the K value around the peak varied according to the $\delta$ value. In general, Rowe\`s stress-dilatancy equation works fairly well from the small strain to the peak.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.87-98
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• 1995

When the crack in orthotropic material is propagating under dynamic model I load, influences of anisotropic property ratio $E_{L}$/ $E_{T}$ on stress and displacement around propagating crack tip are studied in this paper. When M<0.55 and .alpha.=90.deg.(.alpha.; the angle of fiber direction with crack propagating direction, M; crack propagation velocity/shear stress wave velocity), the influence of $E_{L}$/ $E_{T}$ on stress .sigma.$_{x}$, .sigma.$_{y}$, .tau.$_{xy}$ and .sigma.$_{\theta}$ is the greast on .sigma.$_{y}$. Except M<0.55 and .alpha.=90.deg., it is the greast on .sigma.$_{x}$ in any situation. Increasing $E_{L}$/ $E_{T}$, stress components are increased or decreased. When maximum stress is based, the stress .sigma.$_{x}$(.alpha.=90.deg.), .sigma.$_{y}$(.alpha.=0.deg.) and .tau.$_{xy}$ (.alpha.=90.deg.) are decreased with increment of $E_{L}$/ $E_{T}$ in M=0. any stresses except .sigma.$_{*}$x/(.alpha.=0.deg.) are decreased with increment of $E_{L}$/ $E_{T}$ in M=0.9. When .alpha.=90.deg., the influence of $E_{L}$/ $E_{T}$ on displacement U and V is V>U in any velocities of crack propagation, when .alpha.=0.deg., it is VU in M>0.75 and when $E_{L}$/ $E_{T}$ is increased, U and V are decreased in any conditions.sed in any conditions.tions.tions.tions.