Modulus Data Research Articles

Dynamic-Triaxial Tests of Dynamic Shear Modulus and Damping Ratio for sandy silt in Beijing area

To study on relationship between dynamic shear modulus and damping ratio with shear strain, a new dynamic-triaxial test is performed on sandy silt in Beijing area. The testing data of the dynamic-shear modulus are compared with the existing statistical data in Beijing area and the statistical curve to prove the rationality of the test results. Comparsion presents a good agreement.

Holographic dark energy: constraints on the interaction from diverse observational data sets

The present work deals with holographic dark energy models with Hubble horizon as the infra-red cut-off. The interaction rate between dark energy and dark matter has been reconstructed with three different choices of the interaction term. It is shown that the coupling parameter of the interaction term should evolve with redshift to allow the successful transition from decelerated to accelerated phase of expansion. Constraints on the model parameters are obtained from Markov Chain Monte Carlo (MCMC) analysis using the supernova distance modulus data and observational measurements of the Hubble parameter. Results show that the model with the coupling parameter increasing with redshift (z) or equivalently decreasing with the evolution, are ruled out. On the other hand, coupling parameters, increasing or slowly varying with the evolution, are consistent with the observed evolution scenario. A Bayesian evidence calculation has been carried out for statistical selection of the reconstructed models. Though the kinematical parameters are well behaved for these models, the physical variables which determine the nature of the components in the matter sector, are not at all realistic. We have concluded that the existence of spatial curvature is essential for this particular type of dark energy models.

Structural assessment of asphalt pavement condition using backcalculated modulus and field data

Abstract This study aims to assess asphalt pavement condition in terms of backcalculated moduli of asphalt concrete (AC) and unbound material layers. An integrated Artificial Neural Network – Genetic Algorithm (ANN-GA) program was developed to backcalculate layer moduli using pavement surface deflection measured under falling weight deflectometer (FWD) test. Three pavement sections with FWD testing conducted at different time periods were used in the analysis. As damage developed in AC layer over years, the master curve of AC dynamic moduli showed the similar sigmoidal shapes but the modulus decreases as compared to the undamaged AC. The relatively greater variation of modulus degradation was observed for dynamic modulus in the high frequency range. On the other hand, the nonlinearity parameters obtained from backcalculation can be used to characterize modulus distribution at different depths in granular base layer and subgrade. The slight modulus degradation was observed in granular base layer and subgrade. The deterioration trend of AC modulus was found consistent with fatigue cracking measured at pavement surface based on field distress survey results. The study results indicate that FWD testing with advanced analysis can be successfully used to evaluate in situ pavement condition from structural point of view.

Reinvestigation of the Bulk Modulus for fcc Al using a Helmholtz Energy Approach

While extensive studies on the bulk modulus of fcc Al have been conducted, there still exist controversies regarding to the experimental values. In the present work, we adopted a Helmholtz energy approach based on the Morse function, the free electron Fermi gas model, as well as a modified Debye–Gruneisen model ensuring intrinsic thermodynamic relationship satisfied. To identify consistent bulk modulus data, all the model parameters for fcc Al were evaluated by using comprehensively available experimental data on heat capacity, elastic modulus, thermal expansivity, molar volume, etc., over wide temperature and pressure ranges. Reasonable agreements have been achieved in this work without inconsistency among various thermodynamic and thermophysical properties. Our calculated bulk modulus of fcc Al agrees well with the data reported by Kamm and Alers, Gerlich and Fisher, Ho and Ruoff and the assessment done by Wang and Reeber. However, it is impossible to reconcile the parameters to fit the recent data from Raju et al., as well as the results from Tallon and Wolfenden due to the intrinsic thermodynamic constraints.

Simultaneous prediction of rock matrix modulus and critical porosity

The matrix modulus and critical porosity in rocks are two critical parameters to seismic rock physics models; however, the critical porosity is difficult to obtain. Based on the linear relation between the effective bulk modulus and porosity, we propose a fast method for calculating the matrix modulus and critical porosity by least square fitting of effective bulk modulus and porosity data measured in laboratory or field. The proposed method is well suited for samples with wide porosity range. The calculation results accurately reflect the differences in clay content, pressure, and saturation state. Samples with high clay content have low matrix modulus and critical porosity. The matrix modulus is independent of pressure, whereas the critical porosity increases with increasing pressure. The calculated matrix modulus for water-saturated samples is higher than that for dry rock samples.

Mechanical properties, wear resistance and surface damage of glasses and MgAl2O4 spinel ceramic after abrasion and scratch exposure

A transparent spinel ceramic is compared to different types of glasses, including unhardened and hardened material, as well as a polymer in terms of mechanical behavior and optical appearance before and after mechanical exposure. The mechanical behavior of the materials is compared on the basis of depth-sensitive indentation and ring-on-ring bending tests, deriving hardness, elastic modulus, and fracture stress data. The focus of this research is the analysis of specimens after certain exposure times of sand blasting and different loads during scratch tests via weight balance, confocal laser scanning, and optical microscopes to assess wear resistance including surface roughness, mass loss, critical loads, and initial damage. Results are critically discussed in terms of differences in the performance of the diverse materials and the correlation of optical appearance, abrasive behavior, and apparent scratch testing damage. The overall comparison of properties and application relevant to damage resistance indicates that the tested transparent ceramic and the surface hardened Gorilla glass are superior to all other tested variants.

Transport mechanism of deformable micro-gel particle through micropores with mechanical properties characterized by AFM

Deformable micro-gel particles (DMP) have been used to enhanced oil recovery (EOR) in reservoirs with unfavourable conditions. Direct pore-scale understanding of the DMP transport mechanism is important for further improvements of its EOR performance. To consider the interaction between soft particle and fluid in complex pore-throat geometries, we perform an Immersed Boundary-Lattice Boltzmann (IB-LB) simulation of DMP passing through a throat. A spring-network model is used to capture the deformation of DMP. In order to obtain appropriate simulation parameters that represent the real mechanical properties of DMP, we propose a procedure via fitting the DMP elastic modulus data measured by the nano-indentation experiments using Atomic Force Microscope (AFM). The pore-scale modelling obtains the critical pressure of the DMP for different particle-throat diameter ratios and elastic modulus. It is found that two-clog particle transport mode is observed in a contracted throat, the relationship between the critical pressure and the elastic modulus/particle-throat diameter ratio follows a power law. The particle-throat diameter ratio shows a greater impact on the critical pressure difference than the elastic modulus of particles.

PEO: An immobile solvent?

Despite used for half a century as host for salt-polymer complexes, PEO is still not a fossil and due to its availability, remains regularly used as a reference in solvent-free polymer electrolytes and related electrochemical cells. Often qualified as macromolecular solvent or immobile solvent, its drawbacks (crystallinity, mechanical strength) are well identified. On the other hand, its electrolyte conductivity maxima are considered as the best possible in absence of molecular solvents or ionic liquids. The comparison of PEO/LiTFSI based on raw PEO and ultrafiltrated one, shows unambiguously the impact of unentangled oligomers not only on ionic transport but also on mechanical behavior. Conductivity, cationic transference numbers and storage modulus data go in the same direction and the cationic conductivity (O/Li = 30) is divided by 2, following PEO purification.

Artificial Neural Network Approach to Predict the Elastic Modulus from Dynamic Mechanical Analysis Results

AbstractCharacterizing viscoelastic materials over a range of temperatures and strain rates requires an elaborate experimental scheme. Methods are available that allow testing a single specimen and then transform the storage modulus data to recover elastic modulus. However, applying these methods to polymers with more than one thermal transitions is challenging. As the form of artificial neural network (ANN) follows the time–temperature superposition principle, it is used in the present work to establish the master relation for storage modulus. The neural network is built with various neuron numbers and regularization factors, and two magnitudes of Gaussian noises. The predictions achieve the best accuracy when the regularization factor equals 10−4 and neuron number equals the number of thermal transitions in the material. Then the ANN is trained on storage modulus data of graphene‐epoxy nanocomposites and achieves 4.1% average error. The storage modulus is transformed to time domain relaxation function using integral relation of viscoelasticity. Stress response over the strain history is determined and the elastic modulus is extracted. Compared to the tensile test results, the predictions achieve an average error of 0.7%, which indicates that the method can predict the material behavior over a wide range of temperatures and strain rates.

Structural and bio-mineralization features of alumina zirconia composite influenced by the combined Ca2+ and PO43− additions

The structural and bioactivity features of alumina zirconia composite (AZC) due to Ca2+ and PO43− additions are demonstrated. An in situ synthetic approach, starting from the solution precursors is devised for the powder synthesis in which the assorted range of Ca2+ and PO43− additions were done to the equimolar concentrations of Al3+ and Zr4+ precursors. The results witnessed the unique crystallization of tetragonal zirconia (t-ZrO2) at 1100 °C while Ca2+, PO43− and Al2O3 remained in their amorphous state in the system. On further heat treatment, α-Al2O3 crystallized at 1200 °C, which enforced t- → m-ZrO2 transformation while Ca2+ and PO43− still retained their amorphous state. The immersion tests in simulated body fluid (SBF) solution validated the enhanced bio-mineralization activity of AZC due to Ca2+ and PO43− additions. The results from the indentation tests demonstrated good uniformity in the elastic modulus and hardness data of the investigated specimens. Further, in vitro cell culture tests ascertained the bioactivity of all the AZC compositions.

Giant dielectric response in microwave processed CaCu3Ti4O12 ceramics: A correlation among microstructure, dielectric and impedance properties

Polycrystalline CaCu3Ti4O12 (CCTO) ceramics was synthesized by microwave assisted solid-state reaction. Effect of sintering at different temperatures on the crystal structure, dielectric and impedance properties was investigated in detail. Rietveld analysis of X-ray diffraction data identified that crystal structure was a mixture of cubic CCTO and monoclinic CuO phases. Lattice parameters and amount of CuO secondary phase were also estimated as a function of sintering temperature. Microstructural investigation confirmed the existance and successive increase of the melted phase near the grain boundary region with increasing temperature of sintering. Cu-rich nature of the melted phase was further confirmed by selective area EDX spectra. Dielectric and impedance properties were studied as a function of frequency (100Hz to 1MHz) and temperature (room temperature to 300?C). Improvement in dielectric properties as a function of sintering temperature (1000 to 1050?C) was explained in terms of reduction in grain boundary dimension due to the successive increase in Cu-rich melted phase. However, dielectric constant started falling when sintered at 1075?C, which may be accounted in terms of segregation of large amount of CuO phase after a certain temperature and hence a non-stoichiometry of Cu in CCTO lattice. Impedance data were modelled by equivalent electrical circuits to investigate different contributions of electrically heterogeneous systems. In addition, probable relaxationmechanism has been discussed on the basis of impedance and modulus data. Activation energies were calculated from different characterizations and a non-Debye-type relaxation phenomena were observed. In this work, an attempt is made to build up a correlation among synthesis procedure, sintering temperature, dielectric, impedance and microstructural properties.

Structure, dielectric and electrical properties of relaxor lead-free double perovskite: Nd2NiMnO6

In this paper, dielectric relaxor, impedance, AC conductivity and electrical modulus of double perovskite Nd2NiMnO6, prepared by a solid state reaction method and sintered at 1250?C, have been reported in the wide temperature (25-150?C) and frequency (1 kHz-1MHz) ranges. From the preliminary X-ray structural analysis, it is found that the structure of the material is monoclinic. In the study of the temperature dependence of the dielectric constant, the relaxor behaviour of the material is observed. Such type of behaviour is explained by a modified Curie-Weiss and a Vogel-Fulcher law. By analysing Nyquist plots, the existence of grain and grain boundary effects is established. The non-Debye type of relaxation is investigated by the analysis of complex impedance and the modulus data. From the study of impedance data, it is found that the grain resistance is reduced with the increase in temperature indicating the existence of negative temperature coefficient of resistance (NTCR) behaviour in the material which also matches with temperature versus AC conductivity plots. From these results, it may be concluded that this compound may have extreme potential for different high temperature applications.

Fabrication, dielectric and electrical characteristics of 0.94 (BI0.5Na0.5)TiO3-0.06 BaTiO3 ceramics

In the present paper, high temperature synthesis was used to prepare the complex electronic system 0.94 (Bi0.5Na0.5)TiO3-0.06 BaTiO3 (BNT-BT-6). The relationship between the structure and electrical properties have been presented. The crystal data (i.e. unit cell dimensions and tetragonal crystal system) was obtained by preliminary structural analysis using room temperature X-ray diffraction spectra. The unequally distributed and densely packed ceramics were observed in the SEM micrograph of the sintered sample. The vibrational modes of BNT-BT-6 system using room temperature Raman and FT-IR spectra were reported. Temperature and frequency dependent dielectric parameters of BNT-BT-6 exhibit the shift in transition temperature, enhancement of dielectric constant and decrease in dissipation factor of BNT on the addition of BT even in a small amount. Analysis of the frequency and temperature dependent electrical modulus and impedance data of the system shows that the material follows non-Debye type of dielectric relaxation process. The overview of grain effect on the capacitive and resistive characteristics of the BNT-BT-6 material was studied experimentally from the Nyquist plots. Analysis of conductivity spectra was used to calculate activation energy and determine the electrical transport mechanism of the material.

Constraining the dark energy statefinder hierarchy in a kinematic approach

In the present work, we have adopted a kinematic approach for constraining the extended null diagnostic of concordance cosmology, known as the statefinder hierarchy. A Taylor series expansion of the Hubble parameter has been utilised for the reconstruction. The coefficients of the Taylor series expansion are related to the kinematical parameters like the deceleration parameter, cosmological jerk parameter etc. The present values of the kinematical parameters are constrained from the estimated values of those series coefficients. A Markov chain Monte Carlo analysis has been carried out using the observational measurements of Hubble parameter at different redshifts, the distance modulus data of type Ia supernovae and baryon acoustic oscillation data to estimate the coefficient of series expansion of the Hubble parameter. The parameters in the statefinder diagnostic are related to the kinematical parameters. The statefinder diagnostic can form sets of hierarchy according to the order of the kinematical parameters. The present values of statefinder parameters have been constrained. The first set in the statefinder hierarchy allows ΛCDM to be well within the 1-σ confidence region, whereas the second set is in disagreement with the corresponding ΛCDM values at more than 1-σ level. Another dark energy diagnostic, namely the Om-parameters, is found to be consistent with concordance cosmology.

Rheological constitutive equations for glassy polymers, based on trap phenomenology

The present work comprises an upgraded version of a previous research of ours, referring to the evaluation of viscoelastic functions in a broad frequency and time scale. Our analysis is based on the assumption that the polymeric structure consists of an ensemble of meso-regions, with their own energy barrier, which follows a distribution. Through a cooperative process, the meso-regions are linked to each other, and perform rearrangements by changing their positions. The time-dependent behavior is controlled by the distribution energy barriers. In the present analysis, the distribution function will be evaluated by the experimental data of loss modulus. Hereafter, the viscoelastic functions can be evaluated, with further parameters. In addition, the temperature dependence of storage and loss modulus at a constant frequency can be described within the context of the proposed model.

Predicting elastic anisotropy of dual-phase steels based on crystal mechanics and microstructure

This work utilizes mean-field self-consistent and full-field fast Fourier transform-based homogenizations to study the effective elastic behavior of several steels: three dual-phase (DP), DP 590, DP 980, and DP 1180, and one martensitic (MS), MS 1700. Crystallographic textures and phase fractions of these steels are characterized using electron microscopy along with electron-backscattered diffraction to initialize the models. A comprehensive set of Young's modulus and Poisson's ratio data, measured at the ambient temperature as a function of orientation with respect to the rolling direction for each steel sheet, is used to calibrate and validate the models. The calibration of the models enabled us to estimate the single crystal elastic constants for both the martensitic phase and ferrite, while calculating the orientation dependent effective properties. Half of the data was used in the calibration. Subsequent predictions of the orientation dependent effective elastic properties for the remaining data verified that the estimated single crystal properties are reliable. As the steels exhibit a different level of anisotropy in their effective behavior, good predictions allowed us to discuss the role of texture, grain structure, phase fraction and distribution on the effective properties. The results of this work represent a significant incentive to introduce elastic anisotropy in numerical tools for simulating metal forming processes of dual-phase steels, in particular those processes involving springback, using the texture informed crystal mechanics-based models to more accurately estimate the effective elastic properties required by such simulations.

Long-term creep behavior of resin-based polymers in the construction industry

For lifetime assessment of resin-based injection mortar systems in structural applications, a fundamental knowledge of the long-term deformation and failure behavior of such materials is required. This research work addresses the long-term deformation behavior by experimental determination of creep modulus curves for two commercially available epoxy resin (EP) and vinyl ester (VE) resin applied in the construction industry, e.g. for post-installed fastenings, retrofitting and strengthening (FRPCs). The experimental approach involves an accelerated procedure for providing creep modulus data for these complex material systems, considering various material states of practical engineering relevance. Three reference material states were defined as upper and lower bound states, respectively, for the expected creep behavior. They were experimentally accomplished by appropriate temperature and moisture preconditioning. The upper bound reference state I represents and is referred to as the “(fully) cured & dry” state. Conversely, two lower bound reference states representing (a) reference state II “standard-cure – as received” and (b) reference state III “(fully) cured & wet” were defined. For reference state I (upper bound), a stress level of 10 MPa was chosen for the creep experiments at different temperatures, and creep modulus master curves for a temperature of 23 °C and up to 50 years were deduced making use of the time-temperature equivalency principle. The creep modulus curves for the lower bound material reference states II and III were assessed based on modulus reduction factor deduced from short-term tensile experiments together with the functional creep characteristics of the upper bound reference state I. In addition, a hypothetical quasi-worst-case material state as a third “conservative” lower bound state was defined by simply superimposing and hence multiplying the reduction factors for reference states II and III. In this manner, a creep modulus function scatter band for the defined upper and lower bound conditions was achieved, which can be used for deformation modeling and simulation of injection mortar systems. While for the EP resin based resin the effect of curing state was found to be negligible (at least over the range investigated) with the effect of moisture content being more apparent, for the VE resin based resin, both material conditions profoundly affect the creep modulus properties.

A new approach for developing resilient modulus master surface to characterize granular pavement materials and subgrade soils

Resilient modulus is a fundamental material property used for pavement materials characterization. A new methodology for predicting the resilient modulus of unbound/stabilized pavement materials and subgrade soils is developed based on a master surface function at a reference water content. The resilient modulus measurements at different levels of water content are shifted horizontally with respect to the octahedral shear stress, and bulk normal stress; simultaneously. A total of 2754 resilient modulus laboratory measurements, obtained from literature, for five granular base materials, four subgrade soils, one recycled crushed concrete material, and three cement-treated stabilized fine materials are used to evaluate the proposed Master Surface model for the resilient modulus prediction as a function of the stress state, and water content. The proposed predictive methodology is compared to well-known models from literature. The comparison of the investigated models exhibits that the Master Surface model has the most precise and unbiased predictions after numerically optimizing the resilient modulus data.

Multi-scale assessment of mechanical properties of organic-rich shales: A coupled nanoindentation, deconvolution analysis, and homogenization method

The boom of unconventional shale plays has brought significant attention during the last decade to shale rocks. Elastic properties of shale are one of the most important parameters to be known for hydraulic fracturing success which is necessary for production from organic-rich unconventional reservoirs. In this study, we combined experimental methods including, XRD, Rock-Eval, and nanoindentation on eight Bakken Shale samples with various thermal maturity, taken from different wells and depths in the Williston Basin, ND, to examine their mineralogy, and geochemistry with the emphasis on variations on the elastic properties. Expectation Maximization (EM) based statistical deconvolution was applied to the nanoindentation modulus data to distinguish individual mechanical phases. Then homogenization method was used to upscale the elastic properties to macro-scale, and the data were compared with the values reported in the literature. The results showed that the elastic properties of individual mechanical phases could be distinguished and evaluated through a statistical deconvolution approach. Three main mechanical phases were recognized for each shale sample. It was found that homogenized samples have Young's modulus values in the range of 18.2 GPa–38.8 GPa, which were consistent with the range of mechanical property values of the Bakken Shales reported in the literature. Correlative relationship analysis between mineralogy and thermal maturity with elastic properties showed that Young's modulus decreases with increasing TOC content and increases with the increasing maturity.

Comparisons of complex modulus provided by different DMA

Dynamic mechanical analysis (DMA) is one of the most common methods employed to study the materials’ composition and properties. However, the complex modulus estimates provided by DMA are well-known to show divergences between samples and loading clamps. Few works in literature explore these divergences and do not address the mathematical formulation and comparative data of complex modulus in different operational modes provided by different DMA machines. Aiming at contributing to fill this gap, this work presents an investigation on the mathematical formulation for complex modulus determined by this technique and how it is evaluated in three operational modes by three different analyzers. Measurements were performed in single cantilever, dual cantilever and three-point bending modes using basically the same test conditions. Comparisons of the results were made in order to observe the effects of testing equipment and testing parameters.