Volumetric Compressibility Research Articles

The role of adhesive in the ballistic/structural performance of ceramic/polymer–matrix composite hybrid armor

Transient non-linear dynamics computational finite-element analyses are employed to investigate the role of the adhesive used in ceramic strike-face/composite back-face hybrid armor. The role of the adhesive is investigated under: (a) high loading-rate conditions accompanying impact of an armor-piercing projectile onto the armor structure; and (b) low loading rate conditions associated with the ingress of the loads which are generated at the road/tire contact interfaces and transmitted into the armor structure through the vehicle frame. The high loading-rate conditions were analyzed since they reveal the role of the adhesive under ballistic impact scenarios which controls the overall penetration resistance of the armor. On the other hand, the low loading-rate conditions were analyzed since they may reveal the potential structural damage that armor may experience due to sustained in-service loads. Since structural thermoset-polymer-based adhesives suffer from inadequate ductility, only the case of flexible (elastomer-based) adhesives was considered. The following two specific aspects of the adhesive mechanical response are given special attention: (a) strain rate sensitivity and (b) the degree of volumetric compressibility. The results obtained show that while significant improvements in the ballistic protection performance and durability of hybrid armor can be attained by proper modifications in the adhesive layer mechanical properties, there is no single combination of these properties which simultaneously optimizes all the performance requirements.

Investigation on Harmonic Response of Pneumatic Vibration Isolation System with Single and Double-Frequency Excitations

In this paper, a nonlinear model of pneumatic vibration isolator was established, considering the volumetric compressibility of air. Based on this, simulation analyses were done using matlab/simulink software. The response to two different types of disturbances is studied: single-frequency excitation and double-frequency excitation. Single-frequency excitation can induce harmonic frequency response and offset response at the zero frequency. When the frequency is near to the the linearized natural frequency, the harmonic frequency response become stronger. Nonlinear characters have much to do with the drive amplitude. When the drive amplitude become large, the nonlinear characters are more obvious. Double-frequency excitation can induce combination resonance. When the two drive frequencys are close, combination resonance are more strong.

Contribution of the Cytoskeleton to the Compressive Properties and Recovery Behavior of Single Cells

The cytoskeleton is known to play an important role in the biomechanical nature and structure of cells, but its particular function in compressive characteristics has not yet been fully examined. This study focused on the contribution of the main three cytoskeletal elements to the bulk compressive stiffness (as measured by the compressive modulus), volumetric or apparent compressibility changes (as further indicated by apparent Poisson's ratio), and recovery behavior of individual chondrocytes. Before mechanical testing, cytochalasin D, acrylamide, or colchicine was used to disrupt actin microfilaments, intermediate filaments, or microtubules, respectively. Cells were subjected to a range of compressive strains and allowed to recover to equilibrium. Analysis of the video recording for each mechanical event yielded relevant compressive properties and recovery characteristics related to the specific cytoskeletal disrupting agent and as a function of applied axial strain. Inhibition of actin microfilaments had the greatest effect on bulk compressive stiffness (∼50% decrease compared to control). Meanwhile, intermediate filaments and microtubules were each found to play an integral role in either the diminution (compressibility) or retention (incompressibility) of original cell volume during compression. In addition, microtubule disruption had the largest effect on the “critical strain threshold” in cellular mechanical behavior (33% decrease compared to control), as well as the characteristic time for recovery (∼100% increase compared to control). Elucidating the role of the cytoskeleton in the compressive biomechanical behavior of single cells is an important step toward understanding the basis of mechanotransduction and the etiology of cellular disease processes.

Volumetric and Isentropic Compressibility Behavior of Ionic Liquid, 1-Propyl-3-Methylimidazolium Bromide in Acetonitrile, Dimethylformamide, and Dimethylsulfoxide at T = (288.15 to 308.15) K

Density and speed-of-sound data for 1-propyl-3-methylimidazolium bromide ([C3mim][Br]) + acetonitrile (MeCN), [C3mim][Br] + dimethylformamide (DMF), and [C3mim][Br] + dimethylsulfoxide (DMSO) binary mixtures in the dilute concentration region are reported at T = (288.15 to 308.15) K. From these data, apparent molar volume, isentropic compressibility, excess molar volume, and isentropic compressibility deviation values have been calculated. Negative deviations from the ideal behavior of both molar volume and isentropic compressibility have been observed for all systems investigated in this study. It has been found that deviations from ideal behavior for the [C3mim][Br] + MeCN system are larger than those for the [C3mim][Br] + DMF system which, in turn, are larger than those for the [C3mim][Br] + DMSO system. The results have been interpreted in terms of ion–dipole interactions and structural factors of the ionic liquid and investigated organic solvents.

Truss‐type systems exhibiting negative compressibility

AbstractWe propose novel two‐ and three‐dimensional truss structures made from rods of different materials connected together through pin‐joints to form triangular units which can exhibit anomalous compressibility properties. In particular, we show that these systems may be made to exhibit negative linear compressibility along certain directions or compressibilities that are even more positive than any of the component materials, i.e. the end product is a system with tunable compressibility properties that can be tailor made for particular practical applications. We also show that in specific cases, these systems can exhibit an overall negative area compressibility and sometimes even negative volumetric compressibility (i.e. negative bulk modulus) thus confirming that this property can indeed exist. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Preface: phys. stat. sol. (b) 245/11

Preface: phys. stat. sol. (b) 245/11

The immersed/fictitious element method for fluid–structure interaction: Volumetric consistency, compressibility and thin members

AbstractA weak form and an implementation are given for fluid–structure interaction by the immersed/fictitious element method for compressible fluids. The weak form is applicable to models where the fluid is described by Eulerian coordinates while the solid is described by Lagrangian coordinates, which suits their intrinsic characteristics. A unique feature of the method is the treatment of the fictitious fluid by a Lagrangian description, which simplifies the interface conditions. Methods for enforcing volumetric consistency between the fluid and solid and treating thin members are given. Although a compressible viscous fluid is considered here, the new developments can be applied to incompressible fluids. Copyright © 2007 John Wiley & Sons, Ltd.

The effect of plastic fines on the pore pressure generation characteristics of saturated sands

Pore water pressure generation during earthquake shaking initiates liquefaction and affects the shear strength, shear stiffness, deformation, and settlement characteristics of soil deposits. The effect of plastic fines (kaolinite) on pore pressure generation in saturated sands was studied through strain-controlled cyclic triaxial tests. In addition to pore pressure generation, this experimental study also focused on evaluating the threshold shear strain for pore pressure generation and the volumetric compressibility of specimens during pore pressure dissipation. The results reveal that specimens having up to 20% plastic fines content generated larger values of pore water pressure than clean sand specimens. At 30% fines content, the excess pore water pressure decreased below that of clean sand. The threshold shear strain, which indicates the strain level above which pore pressures begin to generate, was assessed for different kaolinite–sand mixtures. The threshold shear strain was similar for 0–20% fines ( γ t∼0.006–0.008%), but increased to about 0.025% for 30% fines. The volumetric compressibility, measured after pore pressure generation, was similar for all specimens. The transition of behavior at fines contents between 20% and 30% can be attributed to a change in the soil structure from one dominated by sand grains to one dominated by fines.

Volumetric and isentropic compressibility behaviour of aqueous solutions of (polyvinylpyrrolidone + sodium citrate) at T = (283.15 to 308.15) K

The apparent specific volumes and isentropic compressibilities have been determined for polyvinylpyrrolidone in aqueous solutions of sodium citrate by density and sound velocity measurements at T = (283.15 to 308.15) K at atmospheric pressure. The results show a positive transfer volume of PVP from an aqueous solution to an aqueous sodium citrate solution. For low concentrations of PVP, the apparent specific volumes of PVP in water increased along with an increase in the polymer mass fraction, while in aqueous sodium citrate solutions decreased along with an increase in the polymer mass fraction. For high concentrations of PVP, the apparent specific volumes of PVP in water and in aqueous sodium citrate solutions were independent of the polymer mass fraction. The apparent specific isentropic compressibility of PVP is negative at T = (283.15 and 288.15) K, which imply that the water molecules around the PVP molecules are less compressible than the water molecules in the bulk solutions. The positive values of apparent specific isentropic compressibility at T = (298.15, 303.15, and 308.15) K imply that the water molecules around the PVP molecules are more compressible than the water molecules in the bulk solutions. Finally, it was found that the apparent specific isentropic compressibility of PVP increases as the concentration of sodium citrate increases.

Brain tissue deforms similarly to filled elastomers and follows consolidation theory

Slow, large deformations of human brain tissue—accompanying cranial vault deformation induced by positional plagiocephaly, occurring during hydrocephalus, and in the convolutional development—has surprisingly received scarce mechanical investigation. Since the effects of these deformations may be important, we performed a systematic series of in vitro experiments on human brain tissue, revealing the following features. (i) Under uniaxial (quasi-static), cyclic loading, brain tissue exhibits a peculiar nonlinear mechanical behaviour, exhibiting hysteresis, Mullins effect and residual strain, qualitatively similar to that observed in filled elastomers. As a consequence, the loading and unloading uniaxial curves have been found to follow the Ogden nonlinear elastic theory of rubber (and its variants to include Mullins effect and permanent strain). (ii) Loaded up to failure, the “shape” of the stress/strain curve qualitatively changes, evidencing softening related to local failure. (iii) Uniaxial (quasi-static) strain experiments under controlled drainage conditions provide the first direct evidence that the tissue obeys consolidation theory involving fluid migration, with properties similar to fine soils, but having much smaller volumetric compressibility. (iv) Our experimental findings also support the existence of a viscous component of the solid phase deformation. Brain tissue should, therefore, be modelled as a porous, fluid-saturated, nonlinear solid with very small volumetric (drained) compressibility.

Elastoplastic Damage Modeling in Unsaturated Rocks and Applications

This paper is devoted to coupled hydromechanical modeling of an underground cavity subjected to excavation, drying, and resaturation. An elastoplastic damage model is proposed for the description of poromechanical behavior of semiductile rocks in saturated and unsaturated conditions. The poroelastic behavior of material is nonlinear and dependent on water saturation degree. The plastic deformation is described using a curved yield surface and a nonassociated flow rule, in order to describe the pressure sensitivity and transition from volumetric compressibility to dilatancy. The evolution of material damage is related to tensile plastic strains. The coupling between plastic deformation and damage is taken into account. The capillary effects on plastic deformation are considered through a generalized effective stress concept. The proposed model is implemented in a finite element code for fully coupled thermohydromechanical problems. An example of application is presented for a cavity subjected to excavation...

Experimental study of consolidation properties of unsaturated soils during draining

AbstractChanges in groundwater elevation may cause a change in the net normal stress and matric potential within the soil mass, which results in volume changes of unsaturated soil. This research investigated the relationship between the drawdown of groundwater and the characteristics of volumetric compressibility of unsaturated soil. Sand column experiments were designed and conducted to measure the volume changes of coarse and fine sands under different types of drainage conditions at fast and slow drainage rates. The finite element program FEMWATER was calibrated and used to simulate the distributions of stress, tension and moisture content within the sands. Finally, based on the changes of net normal stress and matric potential and the observed volume change of the sands, a least‐square method was applied to determine the volumetric consolidation parameters of the unsaturated soils. Copyright © 2004 John Wiley & Sons, Ltd.

DDX diffraction system: A combined diffraction system with EDX and ADX for high-pressure structure studies

A dual dispersive x-ray (DDX) diffraction system which combines energy dispersive x-ray (EDX) diffraction with angle dispersive x-ray (ADX) diffraction has been developed on the cubic-type multianvil press named MAX80 at the beamline NE5C at the TRISTAN Accumulation Ring (6.5 GeV) of the Photon Factory. With the DDX diffraction system, quick recording of the diffraction pattern is made in the EDX diffraction mode for pressure determination and sample identification, and high-quality diffraction patterns with reliable diffraction intensities are obtained in the ADX diffraction mode for structure analysis. It requires only three minutes to switch between the EDX and ADX diffraction modes. The structure relation between Bi iii and Bi iii′ which was suggested by previous researchers has been investigated with this system. The volumetric compressibility was obtained by the EDX diffraction mode and the atomic arrangement was determined from the data collected in the ADX diffraction mode. No significant change was found around the suggested transition pressure. The crystal structure of Bi iii′s is therefore determined to be identical to that of Bi iii.

A general constitutive equation for transient and stationary creep of rock salt

A constitutive equation, which besides creep describes volumetric dilatancy and/or compressibility, is subjected to some restrictions if we would like it to describe both stationary and transient creep. These general formulations are discussed here. A procedure to determine a viscoplastic potential for stationary creep from experimental data is presented. An example is given for rock salt, but the procedure is quite general and can be used for any creeping geomaterial, possessing the property of being either dilatant or compressible. Comparison of the model prediction with the data is presented. Long-term failure, or creep-failure, is also considered. Typical mining examples of creep, wall convergence for both short-term failure and long-term failure are given for vertical shafts or boreholes. Other examples will be given elsewhere.

The mechanical properties of the Microcystis gas vesicle

Gas vesicles isolated from the cyanobacterium Microcystis sp. retained their high stability and critical pressure on storage and could be held under a sustained pressure of 0·5 MPa without collapse. Application and release of pressures up to 0·5 MPa gave reversible changes in volume that indicated an elastic compressibility of 0·0087 MPa−1, which was linear with pressure. The elastic bulk modulus of the Microcystis gas vesicle was 115 MPa. The average yield pressure of the gas vesicles, 4·3 MPa, was determined by infiltrating them with gas at high pressure and then releasing the pressure so that they exploded. From these two measurements the proteinaceous wall of the gas vesicle was calculated to have a Young’s modulus of 3·8 GPa and a yield stress of 78 MPa. These values correspond closely to those of nylon, which has a similar secondary structure to that of the gas vesicle protein. The critical collapse pressure of the Microcystis gas vesicle, 0·8 MPa, is substantially higher than the theoretical buckling pressure, 0·2 MPa, for an unstiffened homogeneous cylinder of similar relative dimensions. The stiffening of the gas vesicle may be provided by its outer layer of GVPc, since the removal of this protein decreases the critical pressure to 0·23 MPa. The volumetric compressibility of the gas vesicle generates a small reversible change in turbidity (0·008 MPa−1). Spectrophotometric measurements showed that a gas vesicle suspension containing 1 μl ml−1 of gas gives a pressure-sensitive optical density of 2·03 cm−1 at a wavelength of 500 nm.

Structure refinement of GeO2 polymorphs at high pressures and temperatures by energy-dispersive spectra of powder diffraction

Profile fitting of energy-dispersive (ED) X-ray diffraction spectra of GeO2 polymorphs, hexagonal (P3221, Z = 3) and tetragonal (P42/mmm, Z = 2), was examined under high-pressure and high-temperature conditions. These ED spectra were observed with a diamond-anvil cell on a synchrotron-radiation source. Structure refinement of hexagonal GeO2 at several pressures was made, in which diffraction intensities were corrected for the energy spectrum of the incident radiation, escape efficiency of the detector, background scattering and absorption. It was confirmed that the Ge—O distances in hexagonal GeO2 vary little with pressure, whereas the mean O—O distance and volume of the GeO4 tetrahedron decrease linearly with pressure. The decrease in the Ge—O—Ge linking angle between tetrahedra causes the deformation of the framework composed of corner-linked tetrahedra, which is mainly responsible for the bulk volume compression. The bulk modulus of the two polymorphs has been calculated on the basis of the volumetric compressibility up to 10 GPa.

Elastic/viscoplastic constitutive equations for rock

Abstract The experimental data needed for the formulation of a constitutive equation to describe the creep of rocks in uniaxial or triaxial tests are reviewed and the influence of loading rate on dilatancy is pointed out. The assumptions which have to be made in obtaining a constitutive equation from these experimental data are specified. A general constitutive equation is then formulated for rocks, which can describe their elastic and viscoplastic properties for any triaxial compressive stress state. Dilatancy and volumetric compressibility of rocks are defined in mathematical terms and so are the concepts of the compressibility/ dilatancy boundary and that of damage. Various time-dependent effects which can be modelled with such a constitutive equation are illustrated. It is shown, for instance, how the loading rate influences the dilatancy and/or the compressibility as well as the various stress-strain curves and the ultimate failure. The peculiarities of the creep phenomenon as described by the model are discussed. Numerical examples are given for several rocks. Various mining engineering problems have already been solved with such constitutive equations.

Thermodynamics of binary polymer alloys. Polyethylene oxide-polymethyl methacrylate system

The phase state and thermodynamic properties of blends of PEO and PMMA of different MM have been studied in the melt. Drop in the crystallinity of PEO to zero (for a PMMA content ⋍0·8 gravimetric fractions), negative deviations from addivity of the specific volume, the coefficients of volumetric thermal expansion and isothermal compressibility and the parameters of the Sanchez-Lacombe equation of state (for a PMMA content in the system ∼0·2) and also the diagram of state of the system are discussed in terms of the existence of specific interactions between the components of the system.

Petrographic Factors Affecting Jointing in the Banded Series, Stillwater Complex, Montana

Joint spacings for two mutually perpendicular joint sets were measured in each of five sample sites in gabbronorites and anorthosites. Joint density ranges from $$3-13 joints/m^{2}$$ for the mafic rocks and from $$1-6 joints/m^{2}$$ for the felsic rocks. Joint spacing varies from 1-128 cm in mafic rocks (average, 4-65 cm) and from 1-300 cm in felsic rocks (average, 9-144 cm). Layer thickness ranges from 1 to 6 m. Mineral mode and clump size consistently show strong relations with joint density and average joint spacing; the higher the mafic mode and the larger the mafic clumps, the greater the joint density and the smaller the average spacing. Felsic grain size decreases with increasing joint density. Layer thickness shows no relation with average spacing for either joint set, with joint density, or with mineral mode. Cooling and unloading could account for most of the differences in joint density because volumetric thermal expansion for pyroxene is about 50% more than for calcic plagioclase, but volumetric compressibility of pyroxene is about 50% less. The initiation of microcracks leading to joints may thus be favored by petrographic contrasts within the rock.

Verdichtung von proben eines dystrandepts und palehumults aus südchile

Samples were taken from one of the upper layers in each of four profiles, two of each of a Dystrandept and a Palehumult. One profile of each kind of soil was in a lightly grazed and the other in a heavily grazed area. The samples were then loaded and unloaded at three different moisture contents. From the compression curves for the samples, the maximum pressure applied to the soil in the past, the compression index, the volumetric compressibility coefficient, the expansion index and the modulus of elasticity were computed. The mechanical coefficients for the Palehumult samples are correlated under both light and heavy loadings with bulk density, moisture contents and past levels of grazing. For the Dystrandept samples under light loadings, however, the coefficients are correlated with degree of aggregation and the nature of the mineral components. In contrast, the relations of the Dystrandept under heavy loading with bulk density and moisture levels are similar to those for the Palehumult samples.