Showing papers on "Material properties published in 1993"
TL;DR: In this article, the authors compared the National Institute of Standards and Technology's Standard Reference Material 720 certificate values for heat capacity with those obtained from recent experimental determinations, which indicated the possibility of a systematic error in the certificate values.
Abstract: Comparison of the National Institute of Standards and Technology’s Standard Reference Material 720 certificate values for heat capacity with those obtained from recent experimental determinations indicated the possibility of a systematic error in the certificate values. Selected experimental determinations of enthalpy increments and heat capacities were fitted in order to obtain a representation of the thermodynamic properties of α‐Al2O3, a sample of which is the standard reference material (SRM‐720) for calibration of some types of calorimeters. The fitted equation and calculated values of the heat capacity, the relative enthalpy, and the entropy are given. The new values are more accurate and result from a better representation of the experimental values than did the 1982 SRM‐720 certificate values. Additionally, the general problem of the effect of changes in practical temperature scales on thermodynamic properties is briefly discussed, using the results for α‐Al2O3. A recent report from the I.U.P.A.C. Commission on Thermodynamics gave a method for the conversion of thermodynamic properties for changes in practical temperature scale. The I.U.P.A.C. method is shown to be not generally correct. A better method for estimation of these changes is given.
356 citations
TL;DR: In this paper, a rigorous and computationally efficient thermodynamic model that estimates the state and composition of atmospheric inorganic species between the gas and aerosol phases is presented, and the estimation of important thermodynamic properties, equilibrium constants, ionic activity coefficients, water activity, and deliquescence points is described.
Abstract: A rigorous and computationally efficient thermodynamic model that estimates the state and composition of atmospheric inorganic species between the gas and aerosol phases is presented. The estimation of important thermodynamic properties, equilibrium constants, ionic activity coefficients, water activity, and deliquescence points is described. Various sources and estimation methods for inorganic gas-liquid-solid equilibrium properties are compared and optimal approaches for the new equilibrium routine are incorporated.
337 citations
TL;DR: In this article, a theoretical study of the deformation of a spherical liquid droplet impinging upon a flat surface is presented, which accounts for the presence of surface tension during the spreading process.
Abstract: This article presents a theoretical study of the deformation of a spherical liquid droplet impinging upon a flat surface. The study accounts for the presence of surface tension during the spreading process. The theoretical model is solved numerically utilizing deforming finite elements and grid generation to simulate accurately the large deformations, as well as the domain nonuniformities characteristic of the spreading process. The results document the effects of impact velocity, droplet diameter, surface tension, and material properties on the fluid dynamics of the deforming droplet. Two liquids with markedly different thermophysical properties, water and liquid tin, are utilized in the numerical simulations because of their relevance in the industrial processes of spray cooling and spray deposition, respectively. The occurrence of droplet recoiling and mass accumulation around the splat periphery are standout features of the numerical simulations and yield a nonmonotonic dependence of the maximum splat radius on time.
308 citations
01 Oct 1993-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, all available thermodynamic and phase diagram data have been critically assessed for all phases in the CaO-Al 2O3, Al2O3-SiO2, and CaO al2O 3-Si2 systems at 1 bar pressure from 298 K to above the liquidus temperatures.
Abstract: All available thermodynamic and phase diagram data have been critically assessed for all phases in the CaO-Al2O3, Al2O3-SiO2, and CaO-Al2O3-SiO2 systems at 1 bar pressure from 298 K to above the liquidus temperatures. All reliable data for the binary systems have been simultaneously optimized to obtain, for each system, one set of model equations for the Gibbs energy of the liquid slag and all solid phases as functions of composition and temperature. The modified quasichemical model was used for the slag. With these binary parameters and those from the optimization of the CaO-SiO2 system reported previously, the quasichemical model was used to predict the thermodynamic properties of the ternary slag. Two additional small ternary parameters were required to reproduce the ternary phase diagram and ternary activity data to within experimental error limits. The calculated optimized phase diagram and thermodynamic properties are self-consistent and are the most reliable currently available estimates of the true values.
263 citations
TL;DR: In this paper, a crack in a strip of Functionally Gradient Material mathematically modeled by a nonhomogeneous solid with the prescribed surface temperature is studied, where all material properties depend only on the coordinate y (perpendicular to the crack faces) in such a way that the properties are some exponential functions of y.
185 citations
TL;DR: A simple physical model of 1-3 composite piezoelectrics that was advanced for the material properties relevant to thickness-mode oscillations is extended to address the hydrostatic response.
Abstract: A simple physical model of 1-3 composite piezoelectrics that was advanced for the material properties relevant to thickness-mode oscillations is extended to address the hydrostatic response. The model is valid when the lateral spatial scale of the composite is sufficiently fine that the composite can be treated as an effective homogeneous medium. Expressions are derived for the composite's material parameters in terms of the volume fraction of piezoelectric ceramic and the properties of the constituent piezoelectric ceramic and passive polymer. The results are similar to those derived by Haun and Newnham (1983, 1986) using a parallel-series connectivity model. The model is illustrated by analyzing composites made from conventional PZT5 and anisotropic modified lead titanate piezoelectric ceramics. For PZT5, the composite structure enhances its hydrostatic charge coefficient, hydrostatic voltage coefficient, hydrophone figure of merit, and hydrostatic coupling coefficient, while three of these quantities fall short of their pure ceramic values in the modified lead titanate composites. The shortfall is due to an enhanced composite that arises from lateral stress on the polymer being transferred to a longitudinal stress along the ceramic rods by the Poisson effect in the polymer, thus producing a charge through the ceramic's d/sub 33/. >
183 citations
TL;DR: In this paper, the effects of the friction coefficient and brake material properties on the critical speeds were examined and the most influential properties were found to be the coefficient of friction and the thermal expansion coefficient of drum materials.
Abstract: Thermoelastic instability in automotive drum brake systems is investigated using a finite layer model with one-sided frictional heating. With realistic material properties of automotive brakes, the stability behavior of the one-sided heating mode is similar to that of the antisymmetric mode of two-sided heating but the critical speed of the former is higher than that of the latter. The effects of the friction coefficient and brake material properties on the critical speeds are examined and the most influential properties are found to be the coefficient of friction and the thermal expansion coefficient of drum materials. Vehicle tests were performed to observe the critical speeds of the drum brake systems with aluminum drum materials. Direct comparisons are made between the calculation and measurement for the critical speed and hot spot spacing. Good agreement is achieved when the critical speeds are calculated using the temperature-dependent friction material properties and the reduced coefficient of friction to account for the effect of intermittent contact.
166 citations
TL;DR: In this paper, an indirect identification technique to predict the mechanical properties of composite plate specimens is presented, which makes use of experimental eigenfrequencies, the corresponding numerical eigenvalue evaluation, sensitivity analysis and optimization.
153 citations
TL;DR: In this paper, all available thermodynamic and phase diagram data have been critically assessed for all phases in the MnO-TiO2, MgO-MgO,TiO 2, FeO-FeO 2, Na2O-Na2O 2 and NaO-K2O 3 systems at 1 bar pressure from 298 K to above the liquidus temperatures, and the modified quasichemical model was used for the molten slag phases.
Abstract: All available thermodynamic and phase diagram data have been critically assessed for all phases in the MnO-TiO2, MgO-TiO2, FeO-TiO2, Ti2O3-TiO2, Na2O-TiO2, and K2O-TiO2 systems at 1 bar pressure from 298 K to above the liquidus temperatures All reliable thermodynamic and phase diagram data have been simultaneously optimized to obtain, for each system, one set of model equations for the Gibbs energy of the liquid slag as a function of composition and temperature and equations for the Gibbs energies of all compounds as functions of temperature The modified quasichemical model was used for the molten slag phases
138 citations
TL;DR: In this paper, a modified quasichemical model was proposed to describe the properties of ordered solutions and represent the measured properties of binary silicates over broad ranges of composition and temperatures.
Abstract: Molten silicates are ordered solutions whose excess Gibbs energies cannot be well represented by the usual polynomial representation of deviations from ideal solution behavior. An adaptation of quasichemical theory has been proposed which is capable of describing the properties of ordered solutions and of representing the measured properties of binary silicates over broad ranges of composition and temperatures. For simple silicates such as the MgO-FeO-SiO2 ternary system in which silica is the only acid component, a combining rule generally leads to good predictions of the thermodynamic properties of ternary (and probably higher order) solutions from those of the binaries. In basic solutions, these predictions are consistent with those of the Conformal Ionic Solution Theory. Our results indicate that our approach could provide a potentially powerful tool for representing and predicting the thermodynamic properties of multicomponent molten silicates. A complete critical evaluation of the thermodynamic properties and phase diagrams of the FeO-MgO, FeO-SiO2, MgO-SiO2 and FeO-MgO-SiO2 systems is presented in which the modified quasichemical model is used for the liquid phase. Optimized equations for the thermodynamic properties of all phases are obtained which reproduce all thermodynamic and phase diagram data to within experimental error limits from 25°C to liquidus temperatures at all compositions. The optimized thermodynamic properties and phase diagrams are the best estimates presently available.
122 citations
TL;DR: In this article, a theory for the prediction of damping and natural frequencies of laminated composite beams with multiple viscoelastic damping layers is described, and the design of composite beams for maximizing the damping capacity is also presented.
Abstract: This paper describes the formulation of a theory for the prediction of damping and natural frequencies of laminated composite beams with multiple viscoelastic damping layers. The damping layers are constrained (or sandwiched) by anisotropic laminates. The in-plane shear strains of the damping layers and the constraining layers are included in the model. Closed-form solutions for the resonance frequencies and modal loss factors of the composite beam system under simple supports are derived using the energy and Ritz method. A parametric study has been conducted to study the variation of dynamic stiffness and modal loss factor of the system with structural parameters (e.g., the ply orientations of laminas, thickness of the damping layers and the laminates), operating temperature, and damping material properties. The design of composite beams for maximizing the damping capacity is also presented in this paper which includes the determination of operating temperature range corresponding to given structural parameters and finding optimal structural parameters corresponding to given temperature range. Finally, some experimental results are compared with theory for the cases of single and double damping layer beam systems that show good agreement between predicted and measured natural frequencies.
TL;DR: In this paper, the Gibbs energies of all phases in Na2OSiO2 and K2O-SiO 2 systems were evaluated at 1 bar pressure from 298 K to above the liq-uidus temperatures.
Abstract: Available thermodynamic and phase diagram data have been evaluated for all phases in the Na2O-SiO2 and K2O-SiO2 systems at 1 bar pressure from 298 K to above the liq-uidus temperatures. All reliable thermodynamic and phase diagram data have been simultaneously optimized in order to obtain one set of model equations for the Gibbs energies of all phases as functions of temperature and composition. The thermodynamic properties and phase diagrams calculated from these parameters are self-consistent. The modified quasi-chemical model was used to represent the Gibbs energies of the molten slag phases.
TL;DR: In this article, a nonlinear theory of plates has been employed to obtain the five nonlinear differential equations with appropriate boundary conditions; these equations are solved numerically with iteration Experiments were conducted at the Glass Research and Testing Laboratory at Texas Tech University, Lubbock, Tex, to validate the mathematical model Laminated glass units 1524 m × 15 24 m (60 in × 60 in) in size with two glass plates each 4763 mm (01875 in) thick with a polyvinyl butyral (PVB) of thickness equal to 152 mm (006 in
Abstract: Laminated glass units for glazing buildings consist of two thin glass plates bonded together by a thin core material, called polyvinyl butyral (PVB) As the plates are usually thin and undergo large lateral displacements, the conventional thin plate theory cannot be applied; instead, a nonlinear theory of plates has to be employed As well, the interlayer, though soft in material properties, provides significant change in the overall behavior of the composite Variational calculus and minimum potential energy theorem are employed to obtain the five nonlinear differential equations with appropriate boundary conditions; these equations are solved numerically with iteration Experiments were conducted at the Glass Research and Testing Laboratory at Texas Tech University, Lubbock, Tex, to validate the mathematical model Laminated glass units 1524 m × 1524 m (60 in × 60 in) in size with two glass plates each 4763 mm (01875 in) thick with a PVB of thickness equal to 152 mm (006 in) were tested up to a lateral pressure of 6895 kPa (1 psi) Lateral displacements and strains at four different locations at the top and bottom of the units were measured The experimental results are compared with those from the mathematical model and presented in this paper
TL;DR: In this paper, the EM plane-wave shielding properties of anisotropic laminated composites are analyzed, based on a model that treats each lamina as a homogeneous and an isotropic sheet and then uses a method that cascades the wave-transmission matrices in the computation, Numerical results are presented for graphite/epoxy laminates.
Abstract: The EM plane-wave shielding properties of anisotropic laminated composites are analyzed, based on a model that treats each lamina as a homogeneous and anisotropic sheet and then uses a method that cascades the wave-transmission matrices in the computation, Numerical results are presented for graphite/epoxy laminates. In particular, the parameters that influence the shielding effectiveness, such as material properties, laminate thickness, fiber orientation and anisotropy of laminates, and angle and polarization of incident wave, are investigated in detail. For design purposes, empirical formulas are also proposed to estimate the shielding effectiveness of the laminated composites in the lower frequency range. >
TL;DR: In this paper, an improved parametric equation for the thermodynamic properties of fluids is presented that incorporates the crossover from singular thermodynamic behavior in the immediate vicinity of the critical point to regular thermodynamic behaviour far away from a critical point.
Abstract: An improved parametric equation for the thermodynamic properties of fluids is presented that incorporates the crossover from singular thermodynamic behavior in the immediate vicinity of the critical point to regular thermodynamic behavior far away from the critical point Based on a comparison with experimental data for ethane and methane, it is demonstrated that the crossover model is capable of representing the thermodynamic properties of fluids in a large range of temperatures and densities around the critical point
TL;DR: Using the Redlich-Kister expression to represent the Gibbs energies of the liquid, fcc and hcp phases in the Al-Zn binary system, the model parameter values were obtained by optimization using thermodynamic and phase equilibrium data available in the literature as discussed by the authors.
Abstract: Using the Redlich-Kister expression to represent the Gibbs energies of the liquid, fcc and hcp phases in the Al-Zn binary system, the model parameter values were obtained by optimization using thermodynamic and phase equilibrium data available in the literature. Not only are the model-calculated values for the thermodynamic properties in agreement with the available experimental data, but also the calculated phase diagram is in agreement with the phase boundary data. The thermodynamic description obtained in the present study is an improvement over the previous descriptions reported in the literature.
TL;DR: In this paper, the authors presented a model-calculated thermodynamic values and phase diagram of binary Al-Mg for the various phases in the binary AlMg and obtained them by optimization using the thermodynamic and phase equilibrium data.
Abstract: Thermodynamic descriptions for the various phases in the binary Al-Mg are presented. These descriptions were obtained by optimization using the thermodynamic and phase equilibrium data available in the literature. The calculated phase diagram of Al-Mg using these thermodynamic descriptions is in excellent agreement with experimental phase equilibrium data reported in the literature. In comparison to earlier evaluations of Al-Mg, we use considerably less model parameters. Yet, the model-calculated thermodynamic values and phase diagram are in good, if not better, agreement with experimental data than those obtained using previous descriptions.
TL;DR: In this article, Chen et al. extended the renormalized Landau expansion to obtain a crossover free energy for binary fluid mixtures in the region around the vapor-liquid critical line.
Abstract: In a previous publication [Z. Y. Chen, A. Abbaci, S. Tang, and J.V. Sengers, Phys. Rev. A 42, 4470 (1990)] a renormalized Landau expansion was constructed for the thermodynamic free energy of one-component fluids that incorporates the crossover from singular thermodynamic behavior at the critical point to regular behavior far away from the critical point. In the present paper the approach is extended to obtain a crossover free energy for binary fluid mixtures in the region around the vapor-liquid critical line. The thermodynamic equations thus obtained are compared with experimental equation-of-state and specific-heat data for mixtures of carbon dioxide and ethane.
TL;DR: In this article, the optimization of the thermodynamic parameters of the various phases existing in the Cr-Ta system was performed taking into account all available thermodynamic and phase diagram data.
Abstract: The optimization of the thermodynamic parameters of the various phases existing in the Cr-Ta system was performed taking into account all available thermodynamic and phase diagram data. The liquid and the two terminal bcc solid solutions were described by a Redlich-Kister equation. The Laves phases, C14 and C15-Cr2Ta, were described by the sublattice model; two different descriptions were used for each of these phases. The set of optimized parameters and the calculated phase diagrams are presented.
TL;DR: Within the linearized theory of heat conduction with fading memory, some restrictions on the constitutive equations are found as a direct consequence of thermodynamic principles as mentioned in this paper, which allow us to obtain existence, uniqueness, and stability results for the solution to the heat flux equation.
Abstract: Within the linearized theory of heat conduction with fading memory, some restrictions on the constitutive equations are found as a direct consequence of thermodynamic principles. Such restrictions allow us to obtain existence, uniqueness, and stability results for the solution to the heat flux equation. Both problems, which respectively occur when the instantaneous conductivity kQ is positive or vanishes, are considered.
TL;DR: A number of useful thermodynamic approximations of wide applicability for describing high-pressure and high-temperature behavior of solids are discussed in this article with particular emphasis on the origin and equivalence of such approximates.
Abstract: A number of useful thermodynamic approximations of wide applicability for describing high-pressure and high-temperature behaviour of solids are discussed with particular emphasis on the origin and equivalence of such approximations. Calculations of various thermodynamic quantities for NaCl crystals are performed and compared with available experimental data to demonstrate the usefulness of the approximations considered.
TL;DR: A quasi-harmonic model has been used to simulate the thermodynamic behavior of the CaCO3 polymorphs, by equilibrating their crystal structures as a function of temperature so as to balance the sum of inner static and thermal pressures against the applied external pressure as discussed by the authors.
Abstract: A quasi-harmonic model has been used to simulate the thermodynamic behaviour of the CaCO3 polymorphs, by equilibrating their crystal structures as a function of temperature so as to balance the sum of inner static and thermal pressures against the applied external pressure. The vibrational frequencies and elastic properties needed have been computed using interatomic potentials based on two-body Born-type functions, with O-C-O angular terms to account for covalency inside the CO3 molecular ion. A good agreement with experimental data is generally shown by simulated heat capacity and entropy, while the thermal expansion coefficient seems to be more difficult to reproduce. The results obtained for aragonite are less satisfactory than those of calcite, but they are improved by using a potential specifically optimized on properties of that phase itself.
TL;DR: In this article, a method for predicting the highly nonlinear stress-strain behavior and dilatation induced by cavitation of highly filled particulate composites from constituent properties has been developed.
Abstract: A method for predicting the highly nonlinear stress-strain behavior and dilatation induced by cavitation of highly filled particulate composites from constituent properties has been developed. The approach presented uses a variation of linear elasticity throughout and has no adjustable parameters, unlike the methods currently used, which require large numbers of fitting factors and complicated nonlinear analyses. An energy balance derived from the first law of thermodynamics calculates critical strain values at which filler particles will debond when subjected to deformation. Repeated calculations of critical strain values using re-evaluated material properties accounting for the damage caused by debonding give very nonlinear stress-strain and dilatation curves. Experimentally observed dependencies on particle size, filler concentration, adhesion, and matrix and filler properties are correctly predicted. The method can be generalized for any state of stress or particle shape. Comparisons of experimental data with the model results give good agreement.
TL;DR: In this article, the Atoms and Bonds approach is applied to the estimation of thermodynamic and physical properties of hydrocarbons, including the standard enthalpy of formation, standard entropy, normal boiling point, standard enthpy of vaporization, critical pressure, critical temperature, and critical volume.
Abstract: Fast and reliable estimation of thermodynamic and physical properties of organic compounds is essential for the analysis and design of chemical processing systems. The ABC approach is based on the contributions of Atoms and Bonds in the properties of Conjugate forms of a molecular structure. The principles of this approach are applied to the estimation of thermodynamic and physical properties of hydrocarbons. Standard enthalpy of formation, standard entropy, normal boiling point, standard enthalpy of vaporization, critical pressure, critical temperature, and critical volume are estimated. Compared to a group-contribution approach, the ABC technique is more accurate, and it involves the same or substantially smaller number of parameters
TL;DR: In this paper, a thermodynamic evaluation of the Cr-Mn and Fe-CrMn systems has been made by using thermodynamic models for the Gibbs energy of the individual phases.
Abstract: A thermodynamic evaluation of the Cr-Mn and Fe-Cr-Mn systems has been made by using thermodynamic models for the Gibbs energy of the individual phases An optimized set of thermodynamic parameters was obtained taking into consideration related experimental information The thermodynamic parameters of the Cr-Mn and Fe-Cr-Mn systems and comparisons between calculation and experimental data are presented
TL;DR: In this article, the complete phase diagram from pure boron to pure nickel at 600-2100°C was calculated using a thermodynamic approach and the thermodynamic mixing properties of the solution phases, as modelled by Redlich-Kister polynomials.
Abstract: The available experimental observations on the equilibrium phase diagram and on the mixing thermodynamics of the Ni–B system have been compiled and critically evaluated. An internally consistent set of thermodynamic model parameters for the solution phases as well as for the intermetallic compounds has been estimated by means of a least squares method and the Lukas program, simultaneously using phase diagram and thermodynamic observations. The complete phase diagram from pure boron to pure nickel at 600–2100°C was calculated using a thermodynamic approach and the thermodynamic mixing properties of the solution phases, as modelled by Redlich–Kister polynomials. The Gibbs energies of formation of the intermetallic phases, described as stoichiometric compounds, have been estimated from the experimental data and refined by means of a least squares treatment. No reliable observations are available on the alloys above 60 at.-%B and, thus, an extrapolated phase diagram has been calculated for the boron ...
TL;DR: In this article, three-dimensional finite element models are used to assess the accuracy of the thermoelastic and thermal properties of unidirectional fiber-reinforced composites predicted by six different micromechanical models.
TL;DR: In this paper, the authors show how the contact structure on the space of thermodynamic parameters M allows the construction of a contact vector field X corresponding to a thermodynamic function, and how the flow associated with such a vector field may be treated as a thermodynamics process if it maps a Legendre manifold representing a given thermodynamic system onto itself.
TL;DR: In this article, isothermal sections of metal-metal-oxygen subsystems of the Al-Ca-Mg-Si-O system were calculated from available thermodynamic descriptions of binary alloy and oxide systems.
Abstract: Isothermal sections of metal-metal-oxygen subsystems of the Al-Ca-Mg-Si-O system were calculated from available thermodynamic descriptions of binary alloy and oxide systems. A comparison with experimental data on the Al-Ca-O system came out less satisfactorily mainly due to the thermodynamic description of the Al-Ca liquid.