• Geomechanics and Engineering
• /
• v.3 no.1
• /
• pp.29-43
• /
• 2011

In this paper a semi-analytical approach is proposed to study the lateral behavior of a piled footing under horizontal loading. As accurate computation of stresses is usually needed at the interface separating the footing (pile) and the soil, this important location should be appropriately modeled as zero-thickness joint element. The piled footing is embedded in elastic soil with either homogeneous modulus or modulus proportional to depth (Gibson's soil). As the pile is the principal element in the piled footing system, a limited parametric study is carried out in order to investigate the influence of footing dimensions and the interface conditions on the lateral behavior of the pile. Hence, the pile behavior is examined through its main governing parameters, namely, the lateral displacement profiles, the bending moments, the shear forces and the soil reactions. The numerical results are presented for Poisson's ratio of 0.2 to represent a large variety of sands and Poisson's ratio of 0.5 to represent undrained clays.

• Journal of Mechanical Science and Technology
• /
• v.19 no.12
• /
• pp.2224-2230
• /
• 2005

In this study, the validity of the Eshelby-type model for predicting the effective Young's modulus and in-plane Poisson's ratio of the 2-dimensional perforated plate has been investigated in terms of the porosity size and its arrangement. The predicted results by the Eshelby-type model are compared with those by finite element analysis. Whenever the ratio of the porosity size to the specimen size becomes smaller than 0.07, the effective elastic constants predicted by finite element analysis are convergent regardless of the arrangement of the porosities. Under these conditions, the effective Young's moduli of the perforated plate can be predicted within the accuracy of $5\%$ by the Eshelby-type model, which overestimates and underestimates the effective Poisson's ratios by $10\%\;and\;6\%$ for the plates with periodically and non-periodically arranged porosities, respectively.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.387-388
• /
• 2006

The influence of porosity (P) on Young's modulus (E) and Poisson's ratio $(\upsilon)$ of sintered steels produced from four types of steel powders was investigated. The values of E and $(\upsilon)$ depend mainly on the value of P, and those were a little affected by alloying elements. The relationships between E, $(\upsilon)$, and P were described as following equations: $E\;=\;E_0{\cdot}(1\;-\;k_E{\cdot}P)^2$ and $\upsilon\;=\;({\upsilon}_0\;-\;\upsilon_{sub}){\cdot}(1\;-\;k_{\upsilon}{\cdot}P)2+\upsilon_{sub}$, where subscript 0 means P = 0, and $k_E,\;k_{\upsilon}$ and ${\upsilon}_{sub}$ are empirical constants. These approximate equations showed good agreement with empirical results.

• Journal of the Korean Wood Science and Technology
• /
• v.41 no.5
• /
• pp.425-431
• /
• 2013

Estimation equations of shear modulus in the plane of laminated veneer lumber (LVL) were compared each other through uniaxial tension test results. The equations - basic elastic equation in the dimensional orthotropic case, Hankinson's formula and empirical equation proposed by Salikis and Falk, were applied to determine the elastic constants at various angles to the grain, which were needed for determination of shear modulus. Tensile elastic modulus of LVL predicted from these equations were compared with test data to evaluate the accuracy of the equation. Tensile elastic modulus rapidly decreased at orientations between 0 and 15 degrees and elastic modulus at grain angles of 15, 30, and 45 degrees overestimated in the presented equations. But the proposed equation by Salikis and Falk showed better prediction, especially at 30, and 45 degrees. This proposed formula would be more useful and practical for estimating of shear modulus of wood composites like LVL to minimize the effect of Poisson's ratio term.

• Journal of the Korean Geotechnical Society
• /
• v.31 no.12
• /
• pp.29-43
• /
• 2015

In this study, engineering property tests were conducted for cement milk used as a filling materials in the bored piles method. For this purpose, various water/cement ratio specimens were produced on the basis of standard specimen specified in highway corporation specifications. The unconfined compressive strength, point load strength, elasticity modulus, poisson's ratio test was performed according to the age. As a test result, injection height for productions of cement milk specimens was defined ratios. Correlation coefficient K of the unconfined compressive strength and point load strength were $K_7=4.55{\sim}13.65$ in age 7 days, and $K_{28}=5.28{\sim}16.84$ in age 28 days. When water / cement ratio is 65-150%, the elastic modulus and Poisson's ratio significantly increased and decreased regardless of age. In addition, the formulae were proposed for unconfined compressive strength, point load strength, a correlation coefficient of unconfined compressive strength, point load strength, elastic modulus, and poisson's ratio for each age.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.28 no.1
• /
• pp.40-45
• /
• 2008

Immersion ultrasonic testing (UT) was used to determine elastic moduli of solid materials instead of the widely-used contact UT method. Conventionally, immersion UT is only used for determining the longitudinal wave speed. However, in this research, transverse wave speed was measured through finding transverse wave echoes caused by mode-conversion at material's boundary. Also, even in the cases when wave speeds could not be determined due to unknown thickness, Poisson's ratio was able to be calculated from the ratio of longitudinal and transverse wave speeds. This technique was verified for several materials, and it was found that higher accuracy was obtained by immersion UT method for materials either with relatively high wave speed or with relatively small Poisson's ratio. This technique thus will be suitable fur ceramics or high strength materials.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.11
• /
• pp.1521-1528
• /
• 2011

We studied the material properties for reliability improvement in finite element analysis results for a nitrile butadiene rubber hub-bearing seal and for a carbon-filled rubber mount used in a vehicle. It was difficult to measure the material properties of hundreds of types of rubber for the mount design. Thus, we suggested that the engineering stressstrain relations from pure shear test data could be synthesized by using simple tension data and Poisson's ratio. We defined Poisson's ratio by using a function of principal stretches to synthesize the stress-strain relations for a pure shear test. A transformation of the pure shear data was applied to the experimental values to obtain the predicted results when the strain approaches 100%. In the finite element analysis for the contact force of a hub-bearing seal, the strain results that used the transformation of the pure shear data and simple tension data almost corresponded to the experimental values. Ogden constants were used to analyze.

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

• The Journal of the Acoustical Society of Korea
• /
• v.25 no.2E
• /
• pp.49-55
• /
• 2006

Compressional wave velocity (Vp), shear wave velocity (Vs), elastic and physical properties, and electrical resistivity for two core sediments obtained from Southeastern Yellow Sea Mud (SEYSM) were measured and computed. The sediments consist of homogeneous mud (mostly silt and clay) with shells and shell fragments. As a result, the mean grain size is uniform ($7.5-8.5{\Phi}$ throughout the core sediments. However, physical properties such as wet bulk density and porosity show slightly increasing and decreasing patterns with depth, compared to the mean grain size. The compressional (about 1475 m/s in average) and shear wave (about 60 m/s in average) velocities with depth accurately reflect the pattern of wet bulk density and porosity. Electrical resistivity is more closely correlated with compressional wave velocity than physical properties. The computed Vp/Vs and Poisson's ratios are relatively higher (more than 10) and lower (approximately 0.002) than Hamilton's (1979) data, respectively, suggesting the typical characteristics of soft and fully water-saturated marine sediments. Thus, the Vp/Vs ratio in soft and unconsolidated sediments is not likely sufficient to examine lithology and sediment properties. Relationships between the elastic constant and physical properties are correlated well. The elastic constants (Poisson's ratio, bulk modulus, shear modulus) given in this paper can be used to characterize soft marine sediments saturated with seawater.

• The Journal of Engineering Geology
• /
• v.15 no.3
• /
• pp.337-348
• /
• 2005

Jurassic granite from Pocheon area were tested to investigate the effect of microcracks on mechanical properties of the granite. Three oriented core specimens were used for uniaxial compressive tests and each core specimen are perpendicular to the axes'R'(rift plane),'c'(grain plane) and'H'(hardway plane), respectively Among vacious elastic constants, the variation of Poisson's ratio as function of the directions was examined. From the related chart between ratio of failure strength and Poisson's ratio, H-specimen shows the highest range in Poisson's ratio and Poisson's ratio decreases in the order of C-specimen and R-specimen. The curve pattern is nearly linear in stage $I\simIII$ but the slope increases abruptly in stage H-3. As shown in the related chart, diverging point of a curve is formed when ratio of failure strength is $0.92\sim0.96$ Stage IV -3 is out of elastic region. The behaviour of rock in the four fracturing stages was analyzed in term of the stress-volumetric strain me. From the stress increment-volumetric strain equations governing the behaviour of rock, characteristic material constants, a, n, Q, m and $\varepsilon_v^{mcf}$, were determined. Among these, inherent microcrack porosity$(a, 10^{-3})$ and compaction exponent(n) in the microcrack closure region(stage I ) show an order of $a^R(3.82)>a^G(3.38)>a^H(2.32)\;and\;n^R(3.69)>n^G(2.79)>n^H(1.99)4, respectively. Especially, critical volumetric microcrack strain($\varepsilon_v^{mcf}$) in the stage W is highest in the H-specimen, normal to the hardway plane. These results indicate a strong correlation between two major sets of microcracks and mechanical properties such as Poisson's ratio and material constants. Correlation of strength anisotropy with microcrack orientation can have important application in rock fracture studies.