Poission's Ratio Research Articles

A comprehensive first-principles investigation of structural, electronic, vibrational, optical, thermodynamic and thermoelectric properties of LiZnAs

The structural, electronic, vibrational, optical, thermodynamic and thermoelectric properties of Nowotny–Juza filled tetrahedral semiconductor LiZnAs under high pressure is investigated using the plane-wave pseudo-potential approach in the frame work of density functional theory (DFT) within the generalized gradient approximation (GGA). The calculated lattice constant (a0) and bulk modulus (B0) at ambient pressure are consistent with earlier reported experiment and theoretical results. The variation in Lattice constant, Bulk modulus (B0), Young modulus (Y), Shear modulus (G), Elastic anisotropy factor (A), Poission ratio (μ), Paugh (B/G) ratio and Elastic constants with pressure is analyzed and concluded. Electronic band structure calculations reveal that with applied pressure direct band gap increases and the indirect band gap decreases. Thermodynamic properties reveals thermodynamically stability with pressurize conditions. The real and imaginary parts of the Dielectric function (ε), Refractive index (η), Extinction Coefficient (k), Optical Conductivity (s), Electron/Optical Energy Loss Function (L), Absorption Coefficient (α), Reflectivity (R) at different pressure conditions are correspondingly studied. With applied pressure the absorption spectra shows a blue shift which makes LiZnAs as potential candidates for the application of optoelectronic devices in ultraviolet frequency range. The thermoelectric properties like Seebeck coefficient (S), Electrical conductivity (σ), and Electronic thermal conductivity (k) and Power factor (PF) have been studied as a function of temperature and chemical potential. Positive value of calculated Seebeck coefficient with temperatures ensures the p-type semiconducting nature of LiZnAs. Results provides theoretical guidance for future experimental investigations and industrial applications of LiZnAs.

Computation of the impact of NiO on physical and mechanical properties for lithium nickel phosphate glasses

In the present study, the nickel oxide doped glasses with the compositions of (40-x)Li2O-xNiO-60P2O5 glasses (where x = 2.5, 7.5,12.5 and 17.5 mol%) have been prepared and their physical and mechanical properties have been studied. Four various glasses coded as NO-2.5, NO-7.5, NO-12.5 and NO-17.5 have been produced and the variation of density, molar volume (VM), specific volume (VS), Metallization factor (M), Young Modulus (Ym), Bulk Modulus (Bm), Shear Modulus (Sm), Longitudinal Modulus (Lm), Poission's ratio (σm) and Micro-Hardness (Hm) have been determined as a function of NiO rate in glass samples. It was seen that the remarkable important effect has been obtained in terms of the NiO rate on these properties.

Continuum Damage Dynamic Model Combined with Transient Elastic Equation and Heat Conduction Equation to Solve RPV Stress

The development of the world cannot be separated from energy: the energy crisis has become a major challenge in this era, and nuclear energy has been applied to many fields. This paper mainly studies the stress change of reaction pressure vessels (RPV). We established several different physical models to solve the same mechanical problem. Numerical methods range from 1D to 3D; the 1D model is mainly based on the mechanical equilibrium equations established by the internal pressure of RPV, the hoop stress, and the axial stress. We found that the hoop stress is twice the axial stress; this model is a rough estimate. For 2D RPV mechanical simulation, we proposed a new method, which combined the continuum damage dynamic model with the transient cross-section finite element method (CDDM-TCFEM). The advantage is that the temperature and shear strain can be linked by the damage factor effect on the elastic model and Poission ratio. The results show that with the increase of temperature (damage factor μ^,d^), the Young’s modulus decreases point by point, and the Poisson’s ratio increases with the increase of temperature (damage factor μ^,Et). The advantage of the CDDM-TCFEM is that the calculation efficiency is high. However, it is unable to obtain the overall mechanical cloud map. In order to solve this problem, we established the axisymmetric finite element model, and the results show that the stress value at both ends of RPV is significantly greater than that in the middle of the container. Meanwhile, the shape changes of 2D and 3D RPV are calculated and visualized. Finally, a 3D thermal–mechanical coupling model is established, and the cloud map of strain and displacement are also visualized. We found that the stress of the vessel wall near the nozzle decreases gradually from the inside surface to the outside, and the hoop stress is slightly larger than the axial stress. The main contribution of this paper is to establish a CDDM-TCFEM model considering the influence of temperature on elastic modulus and Poission ratio. It can dynamically describe the stress change of RPV; we have given the fitting formula of the internal temperature and pressure of RPV changing with time. We also establish a 3D coupling model and use the adaptive mesh to discretize the pipe. The numerical discrete theory of FDM-FEM is given, and the numerical results are visualized well. In addition, we have given error estimation for h-type and p-type adaptive meshes. So, our research can provide mechanical theoretical support for nuclear energy safety applications and RPV design.

Non-Invasive Full Rheological Characterization via Combined Speckle and Brillouin Microscopy

Rheology serves to measure the deformation and flow of materials. Its associated quantities, for example, the Young’s modulus, shear modulus, bulk modulus, or longitudinal modulus, are important in the biomedical field, in particular for soft materials, to characterize the response of materials to external force. Usually, mechanical probes, in particular rheometers or atomic force microscopy, are used to characterize these quantities. In the last decade, optical measurements have been derived to obtain these quantities even in small sample volumes. However, usually only one quantity is evaluated using optical techniques, such as Brillouin microscopy, which does not allow a full rheological characterization. The latter requires measuring at least two quantities, which allows for calculating all further rheological properties. In this paper, we aim to close this gap by combining two optical rheology methods, Brillouin microscopy to measure the longitudinal modulus and Laser Speckle Rheology for the shear modulus. We built an optical setup that allows the non-contact and hence non-destructive and non-invasive measurement of both quantities simultaneously in the same sample using a 780 nm, narrow linewidth (~50 kHz) laser system. We evaluate our approach using defined samples of glycerol and polydimethylsiloxane and we demonstrate image acquisition using the combined setup. We also investigate porcine corneae, as biological samples, and demonstrate direct measurement of longitudinal modulus and shear modulus and calculation of Young’s modulus, bulk modulus, and the Poission ratio, which are all in good agreement with published quantities. In the future, our approach allows for full characterization of the rheology of biological specimens.

Synthesis of MFe2O4 (M=Mg2+, Zn2+, Mn2+) spinel ferrites and their structural, elastic and electron magnetic resonance properties

Structural, elastic and electron magnetic resonance investigations of spinel ferrites with the formula MFe2O4 (M = Mg2+, Zn2+, Mn2+) synthesized by the sol-gel auto-combustion method are reported here. XRD patterns revealed the co-existence of secondary phases along with the ferrite phase. The lattice parameter (8.301 Å, 8.366 Å and 8.434 Å) was found to be varying according to the ionic radii of cations. As determined by scanning electron microscopy (SEM), ZnFe2O4 has a comparatively narrow distribution of grain sizes (1.3–3.8 µm) compared to those in MnFe2O4 (0.8–4.3 µm) and MgFe2O4 (0.3–4.8 µm). The estimated values of average crystallite sizes (17.5 nm, 21.3 nm and 23.3 nm) determined from the X-ray diffraction peaks are considerably less than the average grain sizes (1.3 µm, 1.6 µm and 2.7 µm) estimated from the SEM histograms. The vibrational frequencies in FTIR spectra are in the conformity with the cubic spinel structure and their variation supports the variation of lattice parameter. Equal values of Poission's ratio (0.35) were obtained for the three systems which represent the isotropic behaviour of spinel ferrite systems. The exceptional low value of Lande's g-parameter for ZnFe2O4 indicates the dominance of Fe3+–O–Fe3+ superexchange interaction. Though cation redistribution is possible in the present ferrite systems, the secondary phases existed in these ferrite systems are predominantly influencing the structural, elastic and electron magnetic resonance properties.

Mechanics of Amorphous Lithium Dendrites

The formation of dendrites is a critical drawback for the utilization of Li and other metals in secondary batteries. These emorphous crystals can pierce into the polymer electrolyte and short the cell. Therefore the design/selection criterion requires the dendrite-polymer mechanical compatibility. Hereby we characterize the dendrites morphological evolution based on the intrinsic material property (surface energy). Consequently, we perform force field calculations on the created microstructures to extract the effective mechanical properties such as elastic modulus and poission ratio. In particular, our study is also useful for understanding the mechanics of amorphous structures.

Theoretical study the electronic, elastic properties and thermodynamics properties of ternary phosphide SrPt6P2

The structural, electronic, elastic properties of superconductivity SrPt6P2 have been investigated and analyzed using generalized gradient approximation within the density functional theory. The optimized lattice constant is in well agreement with the experimental data. The total density of states (DOS) results demonstrates that SrPt6P2 is metallic in character, and the Fermi level is mainly the contribution of 5d orbitals of Pt and with small contributions from P-p and Sr-d states. The elastic constants, bulk modulus, Young's modulus and shear modulus are also successfully obtained. The calculated elastic constants meet the mechanical stability criteria. The B/G ratio, Poission's ratio and Cauchy pressure indicated that it possesses ductile. The Vickers hardness is 7.49GPa, suggesting that it is a soft material. Though the quasi-harmonic Debye model, the thermodynamics properties of SrPt6P2 have been obtained. The results show the Cv,Cp and α is about 863.5J/molK, 895.6J/molK and 4.05×105K−1 at 0GPa and 300K, respectively. The Debye temperature is 273.7K, melting temperature is 2271±300K and the minimum thermal conductivities kmin is 0.495Wm−1K−1. It has also been shown that the Cv,Cp and α decrease with increasing pressure at given temperature while increase with increasing temperature at given pressure. Finally, the superconducting parameters are evaluated by the McMillan equation.

Structural and mechanical properties of transition metal borides Nb2MB2 (M=Tc, Ru, and Os) under pressure

Abstract First-principle total energy calculations are employed to provide a fundamental understanding of the structural, mechanical, and electronic properties of transition metal borides Nb 2 MB 2 (M=Tc, Ru, and Os) within the tetragonal superstructure P 4/ mnc structure. The mechanically and dynamically stabilities of three borides have been demonstrated by the elastic constants and phonons calculations under pressure. Among these three compounds, Nb 2 TcB 2 exhibits the biggest bulk and Young's modulus, smallest Poission's ratio, and highest harness. Density of states of them revealed that the strong B–B, Nb–B and M–B covalent bonds are major driving forces for their high bulk and shear moduli as well as small Poisson's ratio.

Effect Of Poisson’s Ratio Of Core Clay On Dynamic Settlement Of The Earth Dams

Construction earth dam is developed to access supply resources. This paper tried to evaluate numerical analysis of the dynamic settlement during the earthquake in different conditions of the Poisson's ratio from core clay. Models were carried out with NAGAN record. ANSYS software is used regard to Finite-element method. Literature indicated that the maximum displacement during the earthquake is conducted at the crest. Interaction between dam and foundation is cased it. Lateral strain is administered the zero so models were considered in plan strain method. This paper considered end of construction with fill up reservoir when the core clay is saturated. Effect of Poisson's ratio on maximum settlement is evaluated. It was regarded the range between 0.2-0.45 for saturate and un saturate respectively. Results indicated that increase of the Poisson's ratio for saturate condition was caused to reduction of the maximum settlement at the crest and middle of core. It is mentioned the end of construction was at the critical state. Due to design of the earth dam regard an increase of construction, control dynamic settlement is required because there are good samples was damaged during the earthquake. Therefore, it is concerned to evaluate and best researches about influence of the dynamic load settlement in the earth dam during an earthquake. Literature review indicated that since the beginning of 1920s and up to 1960s 'Pseudo-static method' of analysis was well-known. However, this method was very simple, and it could not account on the nature of the slope-forming material or the foundation material. Based on deformation characteristics, NEWMARK (8) was proposed 'Sliding block method'. Among other methods, 'Shear beam model' analysis was quite popular. This method was introduced by MONONOBE (7). GAZETAS (3) proposed an improved 'Inhomogeneous shear beam model' which can take care of the fact that the shear modulus in earth or rock-fill dams is not constant but increases with 2/3 power of depth from the crest. CLOUGH and CHOPRA (2) were introduced the finite-element method for two-dimensional plane-strain analysis to estimate the dynamic response of an embankment assuming that it consists of linearly elastic, homogeneous, isotropic materials. Later, several other researchers developed the finite element and finite difference method for non-linear, inelastic, non homogeneous, anisotropic behavior of materials under seismic conditions. ZEGHAL and ABDEL- GHAFFAR (13) were proposed a local-global finite element method of analysis for determination of the non- linear seismic behavior of earth dams. Ming and Li (6) conducted a fully coupled finite-element analysis of failure of Lower San Fernando dam and examined the possible reason of the dam failure. Quick development of computer programs had a useful information of earthquake engineering research. For example, several computer programs like (4, 5, 9and12) were used worldwide for the intensive seismic analysis of the earthen dam. SEID- KARBASI and BYRNE (11) and PIAO et al(10) were represented the dynamic analysis of the earth dams using the finite difference method based computer code FLAC. ZHU et al (1) have presented a two-dimensional analysis of embankment using finite element based program PLAXIS. Shortly, the maximum displacement during the earthquake is induced at the crest. Interaction between dam, and foundation is caused it. This paper considered the effect of Poisson's ratio on maximum settlement at the end of construction regard to two conditions. The first is represented the un saturated dam and second is conducted to saturated dam when it is coupled the reservoir. Briefly, this paper was evaluated the effect of Poission's ratio in clay core on dynamic settlement of the earth dam. II.

Many Body Interactions and Lattice Dynamics of Gold

Lattice dynamics of gold is studied theoretically using phenomenological model. This model considers (i ion-ion and (ii) ionelectron interactions to evaluate the potential energy. Contribution to ion-ion interaction is the sum of two body central interactions between ions and many body interactions among ions. Contribution to potential energy due to ion-electron interactions is evaluated using screened coulomb potential. Using this model phonon frequencies of gold are computed at 48 non-equivalent points of Brillouin zones of crystal and compared with experimental points. Lattice specific heats at different temperatures are evaluated by dividing the frequency spectrum in interval of 0.1 tiga hertz. Using the computed values of lattice specific heats, Debye characteristic temperatures of gold are computed. The model is used to calculate compressibility and Poission's ratio. Agreement of theoretical calculations with experimental results is satisfactory.Key words: Ion-ion interaction; Ion-electron interaction; Phonon frequency; Lattice specific heat; Debye characteristic temperatureThe Himalayan Physics Vol.1, No.1, May, 2010Page: 44-47Uploaded Date: 28 July, 2011

Thermoelastic Analysis of an Annular Sandwich Disk with Metal/Ceramic Faces and Functionally Graded Core

Thermoelastic analysis of a functionally graded annular sandwich disk subjected to nonuniform steady-state thermal load is carried out in this paper. The inner and outer faces of the present disk are made from metal and ceramic materials, respectively. While the core is made from a metal-ceramic functionally graded material. Thermal and mechanical properties of the functionally graded material are assumed to be temperature independent and continuously vary in the radial direction of the disk. The variation of Young's modulus, thermal expansion and conductivity coefficients are represented by a novel exponential law distribution through the radial direction of the disk, but Poission's ratio is kept constant. The governing differential equations are exactly satisfied at every point of the disk. Closed form solutions for the temperature and stress fields are derived in terms of an exponential integral and Whittaker's functions. Some results for stress, strain, and displacement components are presented due to the thermal bending. The distribution of these results during the radial direction of the disk are graphically presented and remarking conclusion is made.

Molecular Dynamics Simulations of trans-1,4,5,8-Tetranitro-1,4,5,8-tetraazadecalin-Based Polymer-Bonded Explosives

Molecular dynamics has been applied to investigate the low-sensitivity explosive TNAD (trans-1,4,5,8-tetranitro-1,4,5,8-tetraazadecalin)-based polymer-bonded explosives (PBXs) with four typical fluorine polymers, PVDF (polyvinylidenedifluoride), PCTFE (polychlorotrifluoroethylene), F(2311) (fluorine rubber), and F(2314) (fluorine resin). The elastic constants, mechanical properties (tensile modulus, bulk modulus, shear modulus, and Poission ratio), binding energies, and detonation performances are first reported for the TNAD-based PBXs. The results show that the mechanical properties of TNAD can be effectively improved by the addition of small amounts of fluorine polymers, and the overall effect of fluorine polymers on the mechanical properties of the PBXs along three crystalline surfaces is (001) > (010) > (100). On each crystal surface, improvement in the ductibility made by the fluorine polymers changes approximately in the sequence of PVDF > F(2311) > F(2314) > PCTFE. The binding energies between different TNAD crystalline surfaces and different polymer binders with the same chain segment or mass fraction both decrease in the order of (010) > (100) > (001). The binding properties of the polymers with the same chain segment on each crystal surface of TNAD increase as PVDF < F(2311) < F(2314) < PCTFE, while those of different polymers in the same content decrease in the sequence of PVDF > F(2311) > F(2314) > PCTFE. The detonation performances of the PBXs decrease in comparison with the pure crystal, but they are superior to those of TNT.

STEADY-STATE THERMOELASTIC ANALYSIS OF A FUNCTIONALLY GRADED ROTATING ANNULAR DISK

This paper is concerned with the thermoelastic analysis of a functionally graded rotating annular disk subjected to a nonuniform steady-state thermal load. Material properties are assumed to be temperature independent and continuously varying in the radial direction of the annular disk. The variations of Young's modulus, material density, thermal expansion and conductivity coefficients are represented by a novel exponential-law distribution through the radial direction of the disk, but Poission's ratio is kept constant. The governing differential equations are exactly satisfied at every point of the disk. Exact solutions for the temperature and stress fields are derived in terms of an exponential integral and Whittaker's functions. Presented are some results for stress, strain and displacement components due to thermal bending of the rotating disk. The effects of angular velocity, inner and outer temperature loads and material properties on the stress, strain and displacement components are discussed.

The Poisson Ratio and Crustal Structure of the Central Tibetan Plateau Inferred from Indepth‐III Teleseismic Waveforms: Geological and Geophysical Implications

AbstractTeleseismic conversion and multiple waves recorded by the INDEPTH III seismic array have been used to investigate the crustal thickness and VP/VS ratios of the central Tibetan Plateau. The comparison with crustal thicknesses obtained from other studies shows good agreement, which suggests that our measurements are reliable. Our results reveal that the crustal thickness is 65±5km beneath central Tibet. On the average, the Moho beneath Qiangtang is 5~6km shallower than that below the Lhasa terrane. A ~10km Moho offset occurs along the BNS, which maybe the result of northward subduction of the Lhasa mantle lid beneath the Qiangtang terrane affected by the India‐Asia collision. Due to extensive crustal melting/fluid beneath the central Tibet, the average crust Poission's ratios are high (0.25~0.32). The high Poission's ratio abnormality in the northern Lhasa may be related to the Bong Co‐Lhari fault. Another high Poission's ratio abnormality located on the northern Qiangtang terrane (st36~st40) can be related to the crustal partial melting arising from the high heat flux from abnormal upper‐mantle beneath the north‐central plateau.

AVO detection of gas-producing dolomite trends in nonproducing limestone

The AVO technique has been successful in hydrocarbon exploration for gas-sand reservoirs such as those in the Texas Gulf Coast, the North Sea, and West Africa, but there are limited examples of successful AVO application in carbonate exploration. Commonly in carbonate reservoirs, dolomitized zones have better reservoir quality than limestones. Because dolomite has a lower Poission's ratio than limestone, AVO might be able to detect dolomite trends. In this paper, we use AVO analysis to detect gas-producing dolomite in the nonproducing Black River limestone. The available data are: (1) NMO-corrected CDP gathers for three 2D lines (lines 1, 2, and 3); (2) log data for five wells: A (a gas dolomite well @ CDP 376) and B (a dry limestone well @ CDP 114) on line 1; C (gas dolomite well @ CDP 486) and D (dry limestone well @ CDP 410) on line 2; and E (dry limestone well @ CDP 148) on line 3. The main zone of interest is the high impedance Lower Ordovician Black River carbonate (Figures 1–3) at depths greater than 8000 ft. This reservoir is believed dolomitized by hydrothermal fluids moving through the host limestone along fractures associated with faults. Well-log data show that the dolomitized reservoir porosity averages about 5%. The limestone is very tight with average porosity less than 2%. Figures 4–8 show the well-log characters of the Black River carbonate in the available wells. Figure 1. Line 1 showing Black River reflector. Figure 2. Line 2 showing Black …

Elastic properties of model random three-dimensional open-cell solids

Most cellular solids are random materials, while practically all theoretical structure–property relations are for periodic models. To generate theoretical results for random models the finite element method (FEM) was used to study the elastic properties of open-cell solids. We have computed the density ( ρ) and microstructure dependence of the Young's modulus ( E) and Poisson's ratio ( ν) for four different isotropic random models. The models were based on Voronoi tessellations, level-cut Gaussian random fields, and nearest neighbour node-bond rules. These models were chosen to broadly represent the structure of foamed solids and other (non-foamed) cellular materials. At low densities, the Young's modulus can be described by the relation E∝ ρ n . The exponent n and constant of proportionality depend on microstructure. We find 1.3< n<3, indicating a more complex dependence than indicated by periodic cell theories, which predict n=1 or 2. The observed variance in the exponent was found to be consistent with experimental data. At low densities we found that ν≈0.25 for three of the four models studied. In contrast, the Voronoi tessellation, which is a common model of foams, became approximately incompressible ( ν≈0.5). This behaviour is not commonly observed experimentally. Our studies showed the result was robust to polydispersity and that a relatively large number (15%) of the bonds must be broken to significantly reduce the low-density Poission's ratio to ν≈0.33.

Thin film characterization by acoustic microscopy

In this paper a brief review of the recent applications of acoustic microscopes for material property determination of thin films is given. Acoustic microscopes generate Rayleigh waves near the surface (up to one or two wave length depth) of the specimen under inspection. Since the Rayleigh wave speed is sensitive to thin film properties such as Young's modulus, Poission's ratio, longitudinal and shear wave speeds, elastic wave attenuation coefficient and density, these properties, in principle, can be extracted from the acoustic microscope generated signals. In this paper it is discussed how one can extract these properties from the V(z) curve generated by an acoustic microscope using the simplex algorithm. V(z) curve is obtained by vertically moving the microscope lens from the specimen surface, thus varying the distance (z) between the focal point of the lens and the reflecting surface of the specimen and recording the corresponding variation of the voltage (V) with z. Extraction of material properties of a thin film specimen from its V(z) curve requires solving the inversion problem, that has not been done by many investigators. The author does it by the simplex algorithm technique which is an optimization technique for solving one or more unknowns in linear or nonlinear equations. Some theoretical and experimental results involving thin (a few micron thick) metal films on a substrate and thin biological cells are also presented in this paper.

Pressure-Sensitive Microvalves Made from Polymer Brushes

AbstractWe describe a novel microvalve, constructed from polymer chains end-grafted onto opposing surfaces of a narrow slit. The assembly of polymer chains acts as both sensor and valve for microflow control and bypasses the need to construct an external feedback mechanism. This microflow control results from densely grafted chains which repel one another and stretch away from the surface, forming a brush which acts as an elastic and impenetrable layer. The height of a sheared brush increases or decreases depending upon solvent quality, i.e the layer can show a negative Poission's ratio. The discharge through the brushlined conduit is a non-linear function of pressure enabling different modes of valve operation. For brushes which extend moderately into the inter-slit region the valve assembly maintains constant discharge over a wide range of pressure. For brushes which extend far into the inter-slit region the valve assembly cuts off flow above a critical pressure, limiting the maximum discharge.

Interpretation of plate load test data

Abstract The International Society for Rock Mechanics (ISRM) has a suggested method for determining in situ the deformability of rock using a plate test. Previous studies using a method of data interpretation that is similar to that recommended by the ISRM show that there is a potential for significant error when interpreting plate load test data. In particular, the determined deformation modulus of a rock mass may be larger than Young's modulus of the intact rock, even where the rock mass is jointed and should intuitively have a deformation modulus that is less than that of the intact rock. Simulations of plate load tests in jointed and unjointed rocks were made using a finite element code to assess some of the effects of jointing and excavation geometry on the determination of the deformation modulus. The results of the simulations are also used to demonstrate a modification of the ISRM suggested method of interpreting plate load test data that should help in interpreting the sometimes apparently counterintuitive results. The proposed modification uses least squares to calculate Young's modulus of the rock mass and also allows Poisson's ratio to be calculated, which is in contrast to the ISRM suggested method that requires Poission's ratio to be known a priori.

一つの不連続面のある岩石試験片の一軸圧縮

For the purpose to investigate the behaviour of jointed rock mass, uniaxial compression tests were performed for specimens each including one artificial joint, horizontal or vertical, and stratiform rock specimens composed of two different rock species which were combined longitudinally. Following results were obtained.1) Strength and deformability of specimens including horizontal joint, are almost equal to those of intact rocks, and are not affected by the planar joint.2) For specimens including vertical joint, both strength and Young's modulus are lower than those of intact rocks.3) For the stratiform specimens, failure occur at the stress, that equals the strength of the weaker rock species which ν/E value (ν: Poission's ratio, E: Young's modulus) is higher. But the mode of failure vary according to combinations of rock species and loading rates. For combination of rock species which strengths are relatively high, both rock species will fail si multaneously. Even for those stratiform specimens, which are composed of two rock species which strengths differ considerably, simultaneous failure may occur in the case of low loading rate. It is considered that the mode of failure results from the interaction of two rock species at the joint.4) It is found by FEM analysis, that failure mode of the stratiform rock specimens mostly depends on the difference of ν/E values of two rock species.