• Journal of Advanced Marine Engineering and Technology
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• v.30 no.6
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• pp.716-723
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• 2006

A meso-scale analysis method using the natural element method is proposed for the analysis of material damage of brittle microcracking solids. The microcracking is assumed to occur along Voronoi edges in the Voronoi diagram generated using the nodal points as the generators. The mechanical effect of microcracks is considered by controlling the material constants in the neighborhood of the micorcracks. The macro elastic moduli of isotropic solids containing a number of randomly distributed microcracks are calculated considering the effect of microcrack closure to demonstrate the validity of the proposed method.

• Journal of the Korean Geotechnical Society
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• v.38 no.10
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• pp.31-40
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• 2022

This study compares elastic moduli calculated using two stiffness testing methods with different strain ranges to evaluate the stress-settlement characteristics of foundation support layers. Elastic moduli were calculated by the soil stiffness gauge (SSG) in the micro-strain range and the plate load test (PLT) in the medium strain range. To apply the elastic moduli obtained by the two testing methods with different strain ranges to the design and construction of foundation soils, the correlation between each measurement value should be identified in advance. As a result of the comparative analysis of the elastic moduli calculated using the two methods in weathered soil and rock, which are representative support layers in Korea, the calculated elastic moduli differed depending on the types of soil and stress conditions. For various soil types, the static elastic modulus obtained by the PLT was reduced by 56% because of the difference in the strain level of the test compared with the dynamic elastic modulus obtained by the SSG. Therefore, the results show that it is necessary to apply corrections to the stress distribution, stress level, and dynamic effect according to the ground stiffness to effectively use the SSG instead of the PLT.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.472-476
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• 2024

It is important that radioactive and nuclear wastes are immobilized in a glass composition with lower melting temperatures due to their economy. In this study, the elastic and mechanical properties of sodium borate-based vitrified radioactive waste were measured using ultrasonic techniques. Many ultrasonic parameters, such as elastic moduli, Poisson's ratio, and microhardness, were calculated by measuring the ultrasonic velocities of the glasses. The ultrasonic velocity data, the density, the calculated elastic moduli, micro-hardness, softening temperature, and Debye temperature depending on the glass composition were evaluated, and the relation with the structure was clarified. It was observed that the elastic modulus and Poisson ratio increased as the Cs₂O content increased in glasses containing Cs waste. This result shows that the rigidity of the network structure of these glasses increases in contrast to the glass containing Sr.

• Structural Engineering and Mechanics
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• v.54 no.5
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• pp.855-875
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• 2015

Many novel materials exhibit a property of different elastic moduli in tension and compression. One such material is graphene, a wonder material, which has the highest strength yet measured. Investigations on buckling problems for structures with different moduli are scarce. To address this new problem, firstly, the nondimensional expression of the relation between offset of neutral axis and deflection curve is derived based on the phased integration method, and then using the energy method, load-deflection relation of the rod is determined; Secondly, based on the improved constitutive model for different moduli, large deformation finite element formulations are developed and combined with the arc-length method, finite element iterative program for rods with different moduli is established to obtain buckling critical loads; Thirdly, material mechanical properties tests of graphite, which is the raw material of graphene, are performed to measure the tensile and compressive elastic moduli, moreover, buckling tests are also conducted to investigate the buckling behavior of this kind of graphite rod. By comparing the calculation results of the energy method and finite element method with those of laboratory tests, the analytical model and finite element numerical model are demonstrated to be accurate and reliable. The results show that it may lead to unsafe results if the classic theory was still adopted to determine the buckling loads of those rods composed of a material having different moduli. The proposed models could provide a novel approach for further investigation of non-linear mechanical behavior for other structures with different moduli.

• Journal of the Korean Geotechnical Society
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• v.31 no.3
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• pp.63-72
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• 2015

This paper describes the correlation and relationship between elastic moduli measured by three stiffness measurement methods with different mechanical characteristics to evaluate the compaction characteristics of subgrade soils. The Soil Stiffness Gauge (SSG) with very small strain (${\approx}0.001%$) ranges, static Plate Loading Test (PLT) with mid-level strain (${\approx}0.01{\sim}0.1%$) ranges, and Dynamic Cone Penetrometer (DCP) using penetration resistance were implemented to measure the elastic modulus. To use the elastic modulus measured by different measurement methods with a wide range of strain in practice, it is required to identify the correlation and relationship of measured values in advance. The comparison results of the measured elastic moduli ($E_{SSG}$, $E_{PLT}$, $E_{DCP}$) using the three measurement methods for domestic and overseas subgrade soils under various conditions indicate that the evaluated elastic modulus relies on the types of soils and the level of stress condition. The correlation analysis of the measured elastic moduli except the data of cement treated soils indicates that the static elastic modulus ($E_{PLT}$) is evaluated as about 60 to 80% of the dynamic elastic modulus ($E_{SSG}$). Unusual soils such as cement treated soils are required to be corrected by the stress correction during the correlation analysis with typical soils, because these types of soils are sensitive to the stress condition when measuring the static elastic modulus ($E_{PLT}$) of soils. In addition, when considering the use of DCP data for the evaluation of the elastic modulus ($E_{DCP}$), the measured data of the elastic modulus less than 200 MPa show more reliable correlation.

• Geotechnical Engineering
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• v.3 no.1
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• pp.53-64
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• 1987

Dynaflect is known as a very effective equipment for the structural evaluation and rehabilitation of Pavements. It is increasingly used in the design, construction and maintenance of the various pavement structures. In this study, two-layered asphalt concrete pavements with the various moduli and thicknesses are selected as the analytical models. The deflections on the surface corresponding to sensor positions of Dynaflect are analyzed utilizing the multi-layered elastic computer program. From the study of the characteristics of spreadability (SPR), it is found that the SPRs are unique when the moduli ratio of pavements EIIE2 are identical. It is also found that the SPR has a linear relationship with the logarithm of moduli ratio ElIE2 in the range of 1.0 to 50. The regression equation to predict the moduli ratio ElyE2 from the SPR and the pavement taickness h is proposed. A series of charts to estimate the elastic moduli of two-layered asphalt concrete pavement system are also developed.

• Journal of the Korean Ceramic Society
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• v.26 no.6
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• pp.850-854
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• 1989

The elastic moduli and dissolution rates of 15 glasses with different mole ratios of sodium-magnasium-phosphate as potential non-toxic biomaterials were investigated. In this study, a 3-pint bending test, sonic resonance technique, and theoretical calculation were used to evaluate the modulus of elasticity. The dissolution rates at 37$^{\circ}C$(human body temperature) were determined by the measurement of mass changes in each sample for 24 weeks.

• Journal of Biomedical Engineering Research
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• v.37 no.2
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• pp.90-103
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• 2016

This research was aimed to analyze load sharing ratios between cortical shell and trabecular bone of a degraded lumbar vertebra with aging, and also evaluate elastic moduli assigned into an FE model, using finite element method. For the better analysis of trabecular bone, effective elastic moduli, that is, nominal elastic moduli divided by the volumetric porosities was used. The elastic moduli of the cortical shell suitable for the trabecular bone were obtained from the equations on the basis of idealized stress-strain relations, including areal porosities. To minimize numerical errors, p-element was used. Using eight parameters that refer to some published papers, the geometry of L3 with a removed posterior part. After the constant compressive displacement was applied, the load sharing ratios were obtained by using both every elastic strain energy and every vertical force between two bones in each 8-volume. As results, 1) according to an increase in age from 20-year to 80-year, load sharing ratios of trabecular bone decreased from 55% to 49%; 2) the maximal ratios of each bone were occurred in the mid-plane of centrums and the endplate of cortical shells, respectively; 3) effective elastic moduli assigned into a porous centrum/cortex were found to be adequate; 4) for load sharing ratios, the difference of two methods showed that the total ratios were almost same within less than 1% but the partial ratios at every depth were more or less different each other.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3C
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• pp.159-166
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• 2008

The stress-strain behavior of soils can usually be regarded as non-linear, while it is also known that the soil exhibits the linear-elastic behavior at pre-failure state (very small strain range, $<10^{-3}%$). This study aims to analyze the variation of anisotropic elastic shear moduli of granular soils in various stress conditions. The stress probe experiments with the triaxial testing device equipped with local strain gages and multi-directional bender elements were conducted. When the stress ratio exceeds the range between -0.5 and 1.5, the elastic shear stiffness in the axial direction deviates from the empirical correlation with current stresses, which indicates that the yielding of soils alters the internal pathway through which the elastic shear wave propagates. The experimental results show that the variation of elastic shear moduli in the horizontal direction closely relates to the volume change of soils.

• Journal of the Korean Wood Science and Technology
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• v.45 no.1
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• pp.20-27
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• 2017

The aim of this paper is to present the modulus of elasticity of $E_L$, $E_R$, $E_T$ along three principal axis of softwood dimension lumber by nondestructive method. Ultrasonic measurement was carried out on defect free wood samples taken by the Japanese Larch, SPF (spruce-pine-fir) and Hem-fir $2{\times}4s$. The ultrasound velocities were measured to calculate young's moduli and it was derived elastic constants for each wood samples using the ultrasound velocities and densities of wood. From the test, $E_L$ was much greater than $E_R$ and $E_T$. $E_R/E_T$ ratios were about 1.3. The high density wood had high young's moduli in three principal axis and the difference in young's moduli between species was greater in transverse direction than longitudinal direction. The anisotropy of the lumber was presented through the calculated elastic moduli and compliances matrix in diagonal term were determined by inverting the stiffness matrix.