• 한국세라믹학회지
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• 제33권5호
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• pp.583-589
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• 1996

In this study a new analytical model which can describe the relationship between the bridging stress and microstructure has beenproposed in order to investigate the microstructural effect on the R-curve behavior in polycrystalline aluminas since the R-curve can be derived via the bridging stress function. In the currently developed model function the distribution of grain size is considered as a microstructural factor in modeling of bridging stress function and thus the bridging stress function including three constants PM, n, and Cx, can be established analytically and quantitatively. The results indicate that the n value is closely related to the grain size distribution thereby providing a reliability of the current model for the bridging stress analysis. Thus this model which explains the correlation of the bridging stress distribution and microstructual parame-ters is useful for the systematic interpretation of microfracture mechanism including the R-curve behavior in polycrystalline aluminas.

• 한국세라믹학회지
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• 제31권12호
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• pp.1449-1458
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• 1994

A new analytical model which can discribe the relationship between the bridging stress and the crack opening displacement was proposed to investigate the microstructural effect on the R-curve behavior in a polycrystalline alumina. The crack opening displacement according to the distance behind the stationary crack tip was measured using in-situ fracture technique in an SEM, and then used for a fitting procedure to obtain the distribution of bridging stress. The current model and an empirical power law relation were introduced into the fitting procedure. The results indicated that the bridging stress function and R-curve computed by the current model were consistent with those computed by the power law relation. The microstructural factor, e.g., the distribution of grain size, was also found to be closely related to the bridging stress. Thus, this model explained well the interaction effect between the distribution of bridging stress and the local-fracture-controlling microstructure, providing important information for the systematic interpretation of microfracture mechanism including R-curve behavior of a monolithic alumina.

• 대한기계학회논문집A
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• 제29권2호
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• pp.284-292
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• 2005

Material flaws in the from of pre-existing defects can severely affect the crack initiation. Stress distribution and crack initiation life of engineering materials such as monolithic aluminum alloy and Al/Glass fiber laminate may be different according to the defect location. The aim of this study is to evaluate effects of relative location of defects around the circular hole in monolithic aluminum and Al/Glass fiber laminates under cyclic bending moment. Stress distribution and crack initiation behavior near a circular hole are considered. Results of Finite Element (FE) model indicated the features of different stress field due to the relative defects positions. Especially, the defects positions at ${\theta}=0^{\circ}\;and\;{\theta}=30^{\circ}$ was strongly effective in stress concentration factor ($K_t$) and crack initiation behavior.

• 한국세라믹학회지
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• 제33권5호
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• pp.602-615
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• 1996

The purpose of the present study is to investigate the microstructural effect on the R-curve behavior in three aluminas with different grain size distributions by analyzing the bridging stress distribution. The crack opening displacement (COD) according to the distance behind the stationary crack tip was measured using an in situ SEM fracture method. The measured COD values in the fine-grained alumina agreed well with Wiederhorn's sollution while they deviated from Wiederhorn's solution in the two coarse-grained aluminas because of the increase of the crack closure due to the grain interface bridging in the crack wake. A numerical fitting procedure was conducted by the introduction of the power-law relation and the current theoretical model together with the measured COD's in order to obtain the bridging stress distribution. The results indicated that the bridging stress function and the R-curve computed by the current model were consistent with those computed by the power-law relation providing a reliable evidence for the bridging stress analysis of the current model. The strain-softening exponent in the power-law relation n, was calculated to be in the range from 2 to 3 and was closely related to the grain size distribution. Thus it was concluded from the current theoretical model that the grain size distribution affected greatly the bridging stress distribution thereby resulting in the quantitative analysis of microfracture of polycrystalline aluminas through correlating the local-fracture-cont-rolling microstructure.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.129-134
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• 1996

Bonding strength of reinforcing material has been recognized to be the most important factor which determines the strengthening effect and the durability of repair work. The properties of bonding layers affects the stress distribution at the end of the plate, therefore the behavior of bonding layer has to be investigated. In this study, the stress distribution at the end of the bonded plate has been tested and compared with Roberts' analysis. Shear stress and vertical normal stress at the end of strengtening plate are analysized and the effedts of bonding layer thickness, plate thickness and plate length on the bonding behavior are tested. The test results showed that thickness is one of the most important factor, which is the thinner the thickness, the smaller the maximum stress.

• Geomechanics and Engineering
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• 제25권4호
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• pp.283-294
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• 2021

This paper presents a rigorous solution for spherical cavity expansion in unsaturated soils under constant suction condition. The hydraulic behavior that describes the saturation-suction relationship is modeled by a void ratio-dependent soil-water characteristic curve, which allows the hydraulic behavior to fully couple with the mechanical behavior that is described by an extended critical state soil model for unsaturated soil through the specific volume. Considering the boundary condition and introducing an auxiliary coordinate, the problem is formulated to a system of first-order differential equations with three principal stress components and suction as basic unknowns, which is solved as an initial value problem. Parameter analyses are conducted to investigate the effects of suction and the overconsolidation ratio on the overall expansion responses, including the pressure-expansion response, the distribution of the stress components around the cavity, and the stress path of the soil during cavity expansion. The results reveal that the expansion pressures and the distribution of the stress components in unsaturated soils are generally higher than those in saturated soils due to the existence of suction.

• Journal of Mechanical Science and Technology
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• 제15권7호
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• pp.965-973
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• 2001

It is well established that arteries are subjected to residual stress. Due to the effect of residual stress, the arteries open to a horse-shoe shape when a longitudinal cut is made on an excised arterial segment. Previously, the residual stress has been quantified by the opening angle of the horse-shoe shape. We have employed a finite element analysis of the open arterial segment to restore the same to the original cylindrical shape and computed the circumferential strain as well as the stress distribution in the wall. In this study, the stress distribution in the femoral arteries of miniswine was computed with and without the residual stress for a range of transmural pressures. Our analysis showed that the residual stress has the effect of redistribution of the circumferential stresses between the intima and the adventitia under physiological loading. The redistribution of the stress with the inclusion of residual stress may be important in the studies on effect of wall stresses on the endothelial and vascular smooth muscle cells.

• 한국농공학회논문집
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• 제53권4호
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• pp.21-27
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• 2011

Soil stress distribution under loading is one of the important problems in civil engineering. Many models have been proposed to interpret the stress distribution in soil and most models assume that the soil is homogeneous and isotropic. Therefore, the actual stress distribution may be different. In addition, With the increase of the top load, soil stress does not increase linearly. In this study, vertical stress changes in sandy soil according to top load increase were measured through experiments. Experimental results, vertical soil stress due to top load increase showed an initial nonlinear behavior and when the load increases to some extent, vertical soil stress showed a linear behavior. ${\alpha}$ value obtained by existing theories always 1.00. But, ${\alpha}$ value by experiment was observed from 0.91 to 1.22 and ${\alpha}$ value was increased with increasing distance from the loading plate.

• Geomechanics and Engineering
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• 제11권2호
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• pp.269-288
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• 2016

The jointed rock mass behavior often plays a major role in the design of underground excavation, and their failures during excavation and in operation, are usually closely related to joints. This research attempts to evaluate the effects of two basic geometric factors influencing tunnel behavior in a jointed rock mass; joints spacing and joints orientation. A hybridized indirect boundary element code known as TFSDDM (Two-dimensional Fictitious Stress Displacement Discontinuity Method) is used to study the stress distribution around the tunnels excavated in jointed rock masses. This numerical analysis revealed that both the dip angle and spacing of joints have important influences on stress distribution on tunnel walls. For example the tensile and compressive tangential stresses at the boundary of the circular tunnel increase by reduction in the joint spacing, and by increase the dip joint angle the tensile stress in the tunnel roof decreases.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.381-388
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• 2003

The material deficiencies in the form of pre-existing defects can initiated cracks and fractures. The stress distribution and fatigue crack initiation life of engineering materials may be associated with the size, the shape and the relative location of defects contained in the component. The objective of this study is to investigate the effect of arbitrarily located hole defect around the rivet hole of a wing section in monolithic aluminum and Al/GFRP laminates under cyclic bending moment during a service load. The stress distribution and the fatigue crack initiation behavior near a rivet hole of on the relationships between stress concentration factor ($K_t$) and relative position of defects were considered. The test results indicated the features of different stress field. Therefore, the stress concentration factor ($K_t$) and the fatigue crack initiation behavior was illustrated different behavior according to each position of hole defect around the rivet hole in monolithic aluminum and Al/GFRP laminates.