• Geomechanics and Engineering
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• v.24 no.3
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• pp.295-305
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• 2021

In this study, design charts for estimating consolidation settlement are proposed according to finite strain consolidation theory using a nonlinear constitutive relationship equation. Results of parametric sensitivity analysis shows that the final settlement, initial height, and initial void ratio exerted the greatest effect, and the coefficients of the void ratio-effective-stress. Proposed design charts were analyzed for three regions using a representative constitutive relationship equation that enables major dredged-reclaimed construction sites in Korea. The regional design charts can be calculated accurately for the final settlement because it is applied directly to the numerical analysis results, except for reading errors. A general design chart applicable to all marine clays is proposed through correlation analysis of the main parameters. A final self-weight consolidation settlement with various initial void ratios and initial height conditions should be estimated easily using the general design chart and constitutive relationship. The estimated final settlement using the general design chart is similar to the results of numerical analysis obtained using finite strain consolidation theory. Under an overburden pressure condition, design charts for estimating consolidation settlement are proposed for three regions in Korea.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.242-245
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• 1998

Effects of the anisotrpy due to the initial textures in the plane sheet on plane strain punch stretching has been investigated. In this study, the anisotropy from textures in the sheet is incoporated into the finite element process model by combining the theory of crstal plasticity. Three different textures such as random texture, plane strain compression texture and cube texture are considered. Variations of puch loads as well as thickness distributions of the sheets with three different initial textures are investigated.

• Geomechanics and Engineering
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• v.16 no.2
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• pp.205-215
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• 2018

Strain-based criteria are known as a direct method in determining the stability of the geomechanical structures. In spite of the widely use of Sakurai critical strain criterion, it is so conservative to make use of them in rocks with initial plastic deformation on account of the considerable difference between the failure and critical strains. In this study, a new criterion has been developed on the basis of the failure strain to attain more reasonable results in determining the stability status of the tunnels excavated in the rocks mostly characterized by plastic-elastic/plastic behavior. Firstly, the stress-strain curve was obtained having conducted uniaxial compression strength tests on 91 samples of eight rock types. Then, the initial plastic deformation was omitted making use of axis translation technique and the criterion was presented allowing for the modified secant modulus and by use of the failure strain. The results depicted that the use of failure strain criterion in such rocks not only decreases the conservativeness of the critical strain criterion up to 42%, but also it determines the stability status of the tunnel more accurately.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.4
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• pp.16-22
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• 2004

Shape optimization was performed to obtain the precise shape of cutouts including the internal shape of cutouts in laminated composite plates by three dimensional modeling using solid element. The volume control of the growth-strain method was implemented and the distributed parameter chosen as Tsai-Hill fracture index for shape optimization. The volume control of the growth-strain method makes Tsai-Hill failure index at each element uniform in laminated composites under the initial volume. Then shapes optimized by Tsai-Hill failure index were compared with those of the initial shapes for the various load conditions and cutouts. The following conclusions were obtained in this study (1) It was found that growth-strain method was applied efficiently to shape optimization of three dimensional cutouts in a laminated composite plate, (2) The optimal shapes on the various load conditions and cutouts were obtained, (3) The maximum Tsai-Hill failure index was reduced up to 67% when shape optimization was performed under the initial volume by volume control of growth-strain method.

• Journal of the Korean Society for Heat Treatment
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• v.37 no.2
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• pp.66-72
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• 2024

To investigate the effect of deformation condition on microstructure and texture formation behaviors of AZ91 magnesium alloy with three kinds of initial texure during high-temperature deformation, plane strain compression tests were carried out at high-temperature deformation conditions - temperature of 673 K~723 K, strain rate of 5 × 10^-3s^-1, up to a strain of -1.0. To clarify the texture formation behavior and crystal orientaion distribution, X-ray diffraction and EBSD measurement were conducted on mid-plane section of the specimens after electroltytic polishing. As a result of this study, it is found that the main component and the accumulation of pole density vary depending on initial texture and deformation caondition, and the formation and development basal texture components ({0001} <$10\bar{1}0$>) were observed regardless of the initial texure in all case of specimens.

• Geomechanics and Engineering
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• v.24 no.1
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• pp.57-65
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• 2021

The effects of initial soil fabric and aspect ratio (AR) on the small-strain stiffness (G0) of granular soils are studied by employing discrete element method (DEM) numerical analysis. Elongated clumps composed of subspheres were adopted, and the G0 values were obtained by DEM simulations of drained triaxial tests under different densities and initial confining pressure (p0). The DEM simulations indicate that the initial soil fabric has an insignificant effect on G0. The effect of the AR on G0 is related to the initial density. Namely, for dense specimens, G0 first increases with increasing AR, reaching a plateau value when the AR ≥ 1.5. However, for loose specimens, G0 gradually increases as the AR increases. Microscopic examination reveals that G0 uniquely depends on the coordination number of the particles (CN-particle) rather than the subspheres (CN-sphere) at the particulate level for the effects of initial soil fabric and AR. Finally, Poisson's ratio ν0 is also determined by CN-particle. In addition, based on data in literature and this study, ν0 can be fitted as ν0 = 5.920(G0/(p0)1/3)-0.99, which can be used to predict ν0 of granular soils based on the measured G0.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.10a
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• pp.298-303
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• 2001

Most of mechanical failures are caused by repeated loadings and therefore they are strongly related to fatigue. To avoid the failures caused by fatigue, determination of an optimal shape of a structure is one of the very important factors in the initial design stage. Shape optimization for a compact tension specimen in opening mode in fracture mechanics, was accomplished by the linear elastic fracture mechanics and the growth-strain method in this study. Also shape optimization for a cantilever beam in mixed mode was carried out by the same techniques. The linear elastic fracture mechanics was used to estimate stress intensity factors and fatigue lives. And the growth-strain method was used to optimize the shape of the initial shape of the specimens. From the results of the shape optimization, it was found that shapes of two types of specimens and a cantilever beam optimized by the growth-strain method prolong their fatigue lives very much. Therefore, it was verified that the growth-strain method is an appropriate technique for shape optimization of a structure having a crack.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.1
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• pp.29-35
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• 2001

Radiation-induced oscillatory instability in CH$_4$/Air diffusion flames is numerically investigated by adopting detailed chemistry. Counterflow diffusion flame is employed as a model flamelet and optically thin gas-phase radiation is assumed. Attention is focused on the extinction regime induced by radiative heat loss, which occurs at low strain rate. Once a steady flame structure is obtained for a prescribed value of initial strain rate, transient solution of the flame is calculated after a finite amount of strain-rate perturbation is imposed on the steady flame. Depending on the initial strain rate and the amount of perturbed strain rate, transient evolution of the flame exhibits various types of flame-evolution behaviors. Basically, the dynamic behaviors can be classified into two types, namely oscillatory decaying solution and diverging solution leading to extinction.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1250-1264
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• 2023

This paper presents approximate in-depth residual stress and plastic strain profiles for laser-peened alloy 600 surface via FE analysis. In approximations, effects of the initial welding residual stress and the number of shots are quantified. Based on FE analysis results, residual stress profiles are quantified by two variables; the maximum difference in stress before and after LSP, and the depth up to which the compressive residual stress exists. Plastic strain profiles are quantified by one variable, the maximum equivalent plastic strain at the surface. The proposed profiles are validated by comparing with published LSP experimental results for welded plates. Effects of the initial welding residual stress and the number of shots on these variables are discussed. The proposed profile can be directly applied to predict the mitigation effect of LSP on PWSCC and to efficiently perform structural integrity assessment of laser peened nuclear components.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.258-263
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• 2001

In this paper, the real-time prediction of high temperature creep life was carried out for the friction welded joints of dissimilar heat resistintg steels (CulCr0.5Zr-STS316L). Various life prediction methods such as LMP (Larson-Miller Parameter) and ISM (initial strain method) were applied. The creep behaviors of those steels and the welds under static load were examined by ISM combined with LMP at 300, 400 and 50$0^{\circ}C$, and the relationship between these two methods was investigated. A real-time creep life (tsub/r/, hr) prediction equation by initial strain ($\varepsilon_0$, %) under any creep stress ($\sigma$, MP$\alpha$) at any high temperature (T, K) was developed