Isothermal Plane Research Articles

The Constitution of Alloys and Phase Diagram of the Ternary Al–Cr–Pt System at 50–100 at.% Pt. I. Solidus Surface and Isothermal Section in the Al–Cr–Pt System at 1350 C in the Range 50–100 at.% Pt

The results of high-temperature diffraction, metallography, X-ray diffraction, electron microprobe analysis, and differential thermal analysis are used to specify the constitution of the Al–Pt system in the near-equiatomic range. The solidus surface is constructed for the first time on the composition triangle, and the constitution of the isothermal section at 1350°C in the range 50–100 at.% Pt of the Al–Cr–Pt ternary system is specified. The solidus surface consists of six single-phase surfaces corresponding to the ternary τ 1 phase (unknown structure), solid solutions based on platinum, and four binary phases existing in the Al–Pt system; nine ruled surfaces bounding two-phase volumes; and four isothermal planes forming invariant four-phase equilibria with participation of a liquid phase. When temperature decreases from subsolidus to 1350°C, stability of the phase based on the compound (low-temperature modification) increases substantially. This phase takes part in equilibria with other intermediate phases and with the Pt-based solid solution.

PIV measurements of a plane wall jet in a confined space at transitional slot Reynolds numbers

Wall jets are important for a wide variety of engineering applications, including ventilation of confined spaces and cooling and drying processes. Although a lot of experimental studies have been devoted to wall jets, many of these have focused on laminar or turbulent wall jets. There is a lack of experimental data on transitional wall jets, especially transitional wall jets released into a confined space or enclosure. This paper presents flow visualizations and high-resolution Particle Image Velocimetry measurements of isothermal transitional plane wall jets injected through a rectangular slot in a confined space. As opposed to many previous studies, not only the wall jet region but also the recirculation region in the remainder of the enclosure is analyzed. The data and analysis in this paper provide new insights into the behavior of transitional plane wall jets in a confined space and will be useful for the validation of numerical simulations of this type of jets.

Constitution of alloys and phase diagram of the Al–Ti–Rh system. III. Solidus surface of the Ti–TiRh–AlRh–Al partial system

The data obtained by metallography, x-ray diffraction, electron microprobe and differential thermal analyses as well as by Pirani–Alterthum incipient melting technique are used to construct the solidus surface projection of the Ti–TiRh–AlRh–Al partial system onto the composition triangle for the first time. The participation of two ternary compounds (τ1, Al67Ti27Rh6, with AuCu3-type structure, and τ2, Al49.6Ti27.1Rh23.3, with Th6Mn23+1-type structure) in phase equilibria is confirmed. Thirteen single-phase surfaces corresponding to solid solutions based on components and to the phases based on binary and ternary compounds are found on the solidus surface. This surface also contains 25 ruled surfaces bounding two-phase volumes as well as 13 isothermal planes that are constituents of invariant four-phase equilibria.

Calculation of the ampacity of high voltage cables by accounting for radiation and solar heating effects using FEM

SUMMARY The paper presents a finite-element model for the evaluation of the ampacity of an underground 110-kV three-phase system of cables in normal operation and in case of emergency. The proposed model takes the effects of convection, radiation, and solar heating at the trench surface into account, which enhances the previous approaches. The calculations performed have shown that these phenomena affect the heating of cables and that the IEC approach that treats the trench surface as an isothermal plane at ambient temperature, widely used in practice, might underestimate the ampacity of cables in certain cases. The model considers in detail the shape and construction of the cable trench, and the thermal properties of backfilling materials and concrete and asphalt covers including the effects of the drying out of soil. The effects of various approximations have been also investigated. The model has been applied to a real life example, and the calculation results have been compared to some experimental data. Copyright © 2011 John Wiley & Sons, Ltd.

Study on Microstructure Evolution of TA1 during Plane Compression and its Similarity to Power Spinning

The hot power spinning process of TA1 has been studied on the base of isothermal plane compression model in this paper. The microstructures of spun workpieces and plane compression specimens are analyzed and the microstructure evolution mechanism has been investigated. The results reveal that the microstructure evolution has similar mechanism between power spinning and plane compression. Plane strain compression can be used to predict and control the microstructure of as-spun TA1 workpiece.

The Al–Cr–Fe phase diagram. I. Phase equilibria at subsolidus temperatures over composition range 58–100 at.% Al

Based on transmission and scanning electron microscopy, x-ray diffraction, electron microprobe and differential thermal analyses, the solidus surface of the ternary Al–Cr–Fe system is constructed for the first time on the concentration triangle over composition range 58–100 at.% Al. Four ternary compounds, D3, O1, H, and e, with decagonal, orthorhombic base-centered, hexagonal, and orthorhombic primitive lattices participate in phase equilibria on the solidus surface. Solid solutions based on aluminum and binary compounds as well as ternary phases form 12 single-phase surfaces, 25 ruled surfaces of two-phase equilibria bounding two-phase regions, and 14 three-phase isothermal planes corresponding to invariant four-phase equilibria on the solidus surface.

The formability of aluminum foam sandwich panels

The present paper aims to study the formability of Aluminum Foam Sandwich (AFS) panels. At now, the final shape of foamed devices is directly obtained through the foaming process itself and no further shaping steps are expected. In any case, further manufacturing processes may be exploited to produce more complex parts. Among forming operations, bending can be regarded as one of the simplest processes for both study and application. Besides, bending tests may yield interesting information about material properties. With regard to the metal foams characterization, several bending tests on AFS panels fabricated by Alulight® were carried out by varying the process conditions. A universal testing machine was employed for this purpose, collecting data about the deformed geometry and about load vs. displacement. Even though the samples deformation was related to the occurrence of foam cells failure or collapse, once the process was terminated, they still retained a significant bending strength. The metal foams properties were also investigated using both non-destructive and mechanical tests. In particular, thickness measurements (using an ultrasonic feeler), X-ray analysis and foam density measurements were carried out on AFS specimens before the execution of both upsetting and bending tests. Finite Element simulations of the foam bending process were performed to investigate stress and strain distributions on the specimens. In particular, an isothermal plane strain model of the bending process was setup using the FEM commercial code Deform 2D. The results of this study were used to produce closed structure components (square shapes) by combining three 90° bends. A further improvement consisted in joining the open ends, to enhance shear and torsion resistance. Among joining techniques conventional welding processes (Tungsten Inert Gas—TIG and laser) and a non-conventional method (Friction Stir Welding—FSW) were investigated. Finally, the mechanical properties of the joints were characterized using both three and four point bending tests.

Molecular dynamics studies on the thermodynamics of supercooled sodium chlorideaqueous solution at different concentrations

In this paper we compare recent results obtained by means of molecular dynamicscomputer simulations on the thermodynamics of TIP4P bulk water and onsolutions of sodium chloride in TIP4P water. The concentrations studied arec = 0.67, 1.36 and2.10 mol kg − 1. The results are checked against change of water–salt potential and size effects. Thesystems are studied in a wide range of temperatures, going from ambient temperature tothe supercooled region. Analysis of simulated state points, performed on the isochores andon the isotherm plane, allowed the determination of the limit of mechanical stability and ofthe temperature of maximum density lines. While the presence of ions in thesystem does not affect the limit of mechanical stability with respect to the bulk, itcauses the temperature of the maximum density line to shift to lower pressureand temperature upon increasing concentration. The occurrence of minima inthe trend of potential energy as a function of density and the inflections in thelow temperature isotherms suggest the presence of liquid–liquid coexistence forbulk water and for the sodium chloride solutions at all concentrations studied.

Surface Morphological Changes in Monolayers of Aromatic Polyamides Containing Various N-Alkyl Side Chains

We synthesized new aromatic polyamides (poly-(N-alkylated benzamides), abbrev. PABA(n)) having both a rigid main chain and a flexible side chain with different lengths. We investigated the solid-state structures, that is, the molecular orientation and surface morphology, of organized molecular films of PABA(n) by performing surface pressure-area (pi-A) isotherm, in-plane and out-of plane X-ray diffraction (XRD), polarized infrared spectroscopy, and atomic force microscopy (AFM) measurements. The solid-state structure of poly-(N-methyl benzamide) (PABA(1)) belonged to the monoclinic system, whereas PABA(3), PABA(4), and PABA(5) showed an orthorhombic packing pattern. PABA(7) and PABA(8) formed amorphous polymers. In the case of PABA(17), a two-dimensional hexagonal lattice was formed as a subcell consisting of side chains. These polymer monolayers were highly condensed on a water surface at 15 degrees C. Out-of-plane XRD measurement results showed that the PABA(1), PABA(3), PABA(4), and PABA(5) multilayers showed large periodicities of 50-60 A. From AFM observation results, it was found that these aromatic polyamides formed single particle layers of hydrophilic groups localized at the bottom of the particles. On the other hand, PABA(7) and PABA(8) monolayers showed irregularity and exhibited shapeless morphologies. In addition, an organized molecular film of PABA(17) formed a highly ordered layer structure (periodicity of 30 A) and a giant circular domain (diameter of 20 nm) made of a side chain crystal. The PABA(17) monolayer showed a hexagonal packing pattern formed due to van der Waals interaction between the flexible side chains. From these experimental findings, it was concluded that the polymer synthesis method employed in the present study can be directly used to control the crystal structure (the third order structure of polymers), molecular arrangement, and surface morphologies of polymer monolayers.

Surface Morphology and Molecular Arrangement of Organized Films of Poly-(N-alkylated benzamides) Containing Various Chain Lengths

We investigated the molecular arrangement and surface morphology of organized molecular films with regard to solid-state structures for newly synthesized aromatic polyamides with various side chain length by surface pressure-area (π–A) isotherm, in-plane and out-of plane X-ray diffraction (XRD), and atomic force microscopy (AFM). Since the aromatic polyamides have rigid main chain and flexible side chain, it may be possible to form the phase separated structure at sub-nanometer scales. These polyamides form the extremely condensed monolayer on the water surface. Multilayers of these polyamides transferred by Langmuir-Blodgett (LB) method construct highly order layer structure. On the other hand, in the two-dimensional film plane of polyamides, amorphous structure of side chains is formed except for octadecyl derivatives. Changes in the surface morphology of monolayers for these polyamides definitely depend on the side chain length. Spherulitic, fibril like, and homogeneous flat morphologies of the film surface are systematically observed by AFM measurement.

Thermal criticality for a reactive gravity driven thin film flow of a third-grade fluid with adiabatic free surface down an inclined plane

This study is devoted to the investigation of thermal criticality for a reactive gravity driven thin film flow of a third-grade fluid with adiabatic free surface down an inclined isothermal plane. It is assumed that the reaction is exothermic under Arrhenius kinetics, neglecting the consumption of the material. The governing non-linear equations for conservation of momentum and energy are obtained and solved by using a new computational approach based on a special type of Hermite-Pade approximation technique implemented in MAPLE. This semi-numerical scheme offers some advantages over solutions obtained with traditional methods such as finite differences, spectral method, and shooting method. It reveals the analytical structure of the solution function. Important properties of overall flow structure including velocity field, temperature field, thermal criticality, and bifurcations are discussed.

Combined Forced and Free Convective Flow in a Vertical Porous Channel: The Effects of Viscous Dissipation and Pressure Work

Buoyant flow is analysed for a vertical fluid saturated porous layer bounded by an isothermal plane and an isoflux plane in the case of a fully developed flow with a parallel velocity field. The effects of viscous dissipation and pressure work are taken into account in the framework of the Oberbeck–Boussinesq approximation scheme and of the Darcy flow model. Momentum and energy balances are combined in a dimensionless nonlinear ordinary differential equation solved numerically by a Runge–Kutta method. Both cases of upward pressure force (upward driven flows) and of downward pressure force (downward driven flows) are examined. The thermal behaviour for upward driven flows and downward driven flows is quite different. For upward driven flows, the combined effects of viscous dissipation and pressure work may produce a net cooling of the fluid even in the case of a positive heat input from the isoflux wall. For downward driven flows, viscous dissipation and pressure work yield a net heating of the fluid. A general reflection on the roles played by the effects of viscous dissipation and pressure work with respect to the Oberbeck–Boussinesq approximation is proposed.

Pattern Competition in Homogeneously Heated Fluid Layers

Simulations examining pattern competition have been performed on a horizontal homogeneously heated layer that is bounded by an isothermal plane above an adiabatic plane. Several different circulation patterns arose as the heating regime applied to the horizontal layer was modified. The sequence of the patterns formed as the Grashof number was increased had the following order: laminar layer, rolls, squares, hexagons and pentagons, and then two square modes of differing orientations. Fourier analysis was used to determine how the key modes interact with each pattern.

Glassy solidification criterion of Zr50Cu40Al10 alloy

We examined the solidification morphology and structure of arc-melted Zr50Cu40Al10 glass-forming alloys. Since the crystal growth rate is much lower than the velocity of isothermal plane of glass transition temperature (Tg), arc-melted Zr50Cu40Al10 alloy sometimes reveals glassy phase at finally solidified region (top-side) after crystal growth (bottom side). Vitrification in front of the crystalline solidification interface of arc-melted Zr50Cu40Al10 alloy Zr can be seen when the crystal phase is an Al-supersaturated B2-type ZrCu phase.

Stability of plane Poiseuille–Couette flows of a piezo-viscous fluid

We examine stability of fully developed isothermal unidirectional plane Poiseuille–Couette flows of an incompressible fluid whose viscosity depends linearly on the pressure as previously considered in Hron et al. [J. Hron, J. Málek, K.R. Rajagopal, Simple flows of fluids with pressure-dependent viscosities, Proc. R. Soc. Lond. A 457 (2001) 1603–1622] and Suslov and Tran [S.A. Suslov, T.D. Tran, Revisiting plane Couette–Poiseuille flows of a piezo-viscous fluid, J. Non-Newtonian Fluid Mech. 154 (2008) 170–178]. Stability results for a piezo-viscous fluid are compared with those for a Newtonian fluid with constant viscosity. We show that piezo-viscous effects generally lead to stabilisation of a primary flow when the applied pressure gradient is increased. We also show that the flow becomes less stable as the pressure and therefore the fluid viscosity decrease downstream. These features drastically distinguish flows of a piezo-viscous fluid from those of its constant-viscosity counterpart. At the same time the increase in the boundary velocity results in a flow stabilisation which is similar to that observed in Newtonian fluids with constant viscosity.

Revisiting plane Couette–Poiseuille flows of a piezo-viscous fluid

We re-examine fully developed isothermal unidirectional plane Couette–Poiseuille flows of an incompressible fluid whose viscosity depends linearly on the pressure as previously considered in [J. Hron, J. Málek, K.R. Rajagopal, Simple flows of fluids with pressure-dependent viscosities, Proc. R. Soc. Lond. A 457 (2001) 1603–1622]. We show that the conclusion made there that, in contrast to Newtonian and power-law fluids, piezo-viscous fluids allow multiple solutions is not justified, and that the inflection velocity profiles reported in [J. Hron, J. Málek, K.R. Rajagopal, Simple flows of fluids with pressure-dependent viscosities, Proc. R. Soc. Lond. A 457 (2001) 1603–1622] cannot exist. Subsequently, we undertake a systematic parametric study of these flows and identify three distinct families of solutions which can exist in the considered geometry. One of these families has no similar counterpart for fluids with pressure-independent viscosity. We also show that the critical wall speed exists beyond which Poiseuille-type flows are impossible regardless of the magnitude of the applied pressure gradient. For smaller wall speeds channel choking occurs for Poiseuille-type flows at large pressure gradients. These features distinguish drastically piezo-viscous fluids from their Newtonian and power-law counterparts.

Numerical Study of the Inlet Conditions Influence on Laminar Plane Wall Jets

In this paper, we present a numerical investigation of a laminar isothermal plane two dimensional wall jets. Special attention has been paid to the effect of the inlet conditions at the nozzle exit on the flow thermal characteristics in forced convection regime. Two velocities profiles at the nozzle exit are used: uniform profile and parabolic profile. The system of equations governing the studied configuration is solved with a finite difference scheme and an implicit scheme, for numerical stability we use a staggered non uniform grid. The obtained results show, first, that the inlet conditions affect the flow in the immediate neighbourhood of the nozzle (core region) in which the flow is governed mainly by the inertias forces. At the established region the results become independent of the flow inlet conditions.

Alloys and phase equilibria in the Al-Ti-Rh system. I. Solidus surface of the TiRh-Rh-AlRh partial system

The data of metallography, x-ray diffraction, electron microprobe, and differential thermal analyses are used to project the solidus surface of the partial TiRh-Rh-AlRh system onto the concentration triangle for the first time. No ternary compounds are found in this system. It is established that there are four single-phase surfaces corresponding to the rhodium solid solution, phases based on Ti3Rh5 and TiRh3 compounds, and the δ phase (continuous series of solid solutions between isostructural CsCl-type AlRh-based phases and high-temperature modification of the TiRh-based phase). The solidus surface also contains five ruled surfaces bounding two-phase volumes and two isothermal planes that are constituents of invariant four-phase equilibria reached at 1714 and 1675°C, respectively.

Enhancement of Structural Fluctuation in the Region Connecting Two Kinds of Critical Points in Temperature−Pressure−Composition Three-Dimensional Phase Diagram: Raman Studies of Benzene/CO2 Binary Systems up to Supercritical Region

Pressure dependence of Raman spectra of benzene/CO2 two-component systems was systematically studied at different temperatures and compositions. We estimated the magnitude of inhomogeneous component in Raman bandwidth to get information on the structural fluctuation in the system. It was found that the inhomogeneous bandwidth attains a maximum on an isothermal plane in the temperature-pressure-composition three-dimensional phase diagram when the state point crosses the line connecting the region where the density fluctuation is large (the vicinity of the critical point of neat CO2) and the region where the concentration fluctuation in a binary system is enhanced (the vicinity of the critical solution point). By accumulating such data, we found that the points of large structural fluctuation comprise a sheet that includes the extension line of the gas-liquid equilibrium line in the phase diagram of neat CO2 and the line connecting critical solution points of the two-component system at different temperatures. Interaction between benzene and CO2 molecules in the supercritical region is briefly discussed.

Measurement of flow stress in hot plane strain compression tests

This Good Practice Guide is applicable to hot (isothermal) plane strain compression (PSC) tests at medium to high rates of strain (10–3 to 102 s–1) at deformation temperatures below the solidus.Guidance is provided on appropriate testpiece geometries and methods of verifying the temperature distribution along the length of the testpiece. Flow diagrams are given showing all the steps that are necessary, including the correction factors that need to be applied for breadth spreading of the testpiece; machine origin and compliance, friction effects and deformational heating. Details are given of the calibration procedures that should be followed to provide traceability to the National Measurement System.The development of the procedure has been supported through experimental tests on type 316 austenitic stainless steel at 1050–1150°C and an aluminium alloy, AA5052, at 300°C to 500°C at strain rates ranging up to 100 s–1.Technical input to the document has been provided by a steering group comprising academic researchers, representatives of industrial users and producers of a wide range of engineering materials.