Identical Aluminum Research Articles

A Novel High-temperature Aircraft-specific Energy Harvester Using PCMs and State of the art TEGs

Energy self-sufficiency is a key enabling factor in realizing any truly autonomous and completely wireless system. With regard to aeronautical applications, creating autonomous wireless sensor nodes can potentially help to drive the maintenance costs for civil aviation companies down, by converting some of the regular maintenance checks to an on demand basis. Thermoelectric energy harvesting can be used in environments where temperature differences occur naturally or are a byproduct of a process, preferentially in areas difficult to reach. By using phase change materials (PCMs) attached to one side of a thermoelectric generator (TEG), the temperature difference across the device can be temporarily enhanced, leading to increased electrical energy production. Thermoelectric energy harvesting using PCMs has been previously explored as an electrical energy source, in sub-freezing temperature environments and its potential has been evaluated most recently both theoretically and experimentally, but most importantly proven over a six month flight test campaign. Furthermore, the performance of tailored TEGs in combination with different PCMs has been studied up to temperatures of 190°C. In order to expand on previous results, state of the art TEG sets made by Micropelt were installed on two identical aluminium containers. The containers were redesigned to include a mounting ring for easier aircraft installation. Simulations as well as experiments in a climate chamber and on a hot plate were performed. With the latter approach the heating rates typically found near the pylon area are mimicked whereas the first is used to assess different potential ambient conditions in general. In addition, previously used erythritol is compared to H120 offered by PCM-Products Ltd., allowing to investigate and to evaluate the effect different PCMs have on the energy output.

Characterization of Aging Behavior of AA6061 Aluminum Alloy Through Destructive and Ultrasonic Non-destructive Testing Techniques

An experiment was conducted to characterize microstructural and mechanical behavior of AA6061 alloy during an artificial aging treatment through destructive and ultrasonic nondestructive techniques. Identical aluminum plates of AA6061-T6 aluminum alloy were solutionized at ≈800 K, followed by quenching and artificial aging at 493 K up to 8 h. The microstructural evolution was analyzed using scanning electron microscopy. The variations in hardness, yield stress, and ultimate tensile strength with respect to aging time were discussed. Besides, ultrasonic parameters velocity and attenuation were measured and correlated with the microstructural evolution as well as certain mechanical properties. The ultrasonic measurements showed a good correlation with the microstructural features and mechanical properties of the alloy during aging, whereby an excellent correlation was found between the longitudinal wave velocity and strength properties of the aged specimens. The longitudinal wave velocity was found to be directly related to the hardness with a correlation coefficient of 0.99.

Ballistic Resistance of Honeycomb Sandwich Panels under In‐Plane High‐Velocity Impact

The dynamic responses of honeycomb sandwich panels (HSPs) subjected to in-plane projectile impact were studied by means of explicit nonlinear finite element simulations using LS-DYNA. The HSPs consisted of two identical aluminum alloy face-sheets and an aluminum honeycomb core featuring three types of unit cell configurations (regular, rectangular-shaped, and reentrant hexagons). The ballistic resistances of HSPs with the three core configurations were first analyzed. It was found that the HSP with the reentrant auxetic honeycomb core has the best ballistic resistance, due to the negative Poisson's ratio effect of the core. Parametric studies were then carried out to clarify the influences of both macroscopic (face-sheet and core thicknesses, core relative density) and mesoscopic (unit cell angle and size) parameters on the ballistic responses of the auxetic HSPs. Numerical results show that the perforation resistant capabilities of the auxetic HSPs increase as the values of the macroscopic parameters increase. However, the mesoscopic parameters show nonmonotonic effects on the panels' ballistic capacities. The empirical equations for projectile residual velocities were formulated in terms of impact velocity and the structural parameters. It was also found that the blunter projectiles result in higher ballistic limits of the auxetic HSPs.

Material hardness and ageing measurement using guided ultrasonic waves

Elastic properties of materials can be easily determined from the ultrasonic wave velocity measurement. However, material hardness cannot be obtained from the ultrasonic wave speed. Heat treatment and ageing affect the microstructure of many materials changing their hardness and strength. It has been already established that ultrasonic attenuation and dispersion are also affected by the material microstructure. It is investigated in this paper if the attenuation of ultrasonic guided waves can be correlated with the material ageing or duration of heat treatment and material hardness. To this aim six identical aluminum 2024 alloy plate specimens were subjected to different durations of heat treatment at 150°C and were inspected nondestructively propagating Lamb waves through the specimens. Attenuation of the Lamb wave was found to be inversely related to the hardness. Rockwell hardness test was performed to corroborate the ultrasonic observations. In comparison to the Rockwell hardness test the ultrasonic inspection was found to be more sensitive to the heat treatment duration and material ageing. From these results it is concluded that guided wave inspection method is a reliable and probably more desirable alternative for characterizing the hardness and microstructure of heat treated materials. Earlier investigations correlated the bulk wave attenuation with the material ageing while this work is the first attempt to correlate the guided wave attenuation to the material hardness and ageing.

Calorímetro diferencial para estudo do padrão de aquecimento gerado por feixes ultrassônicos terapêuticos

The present work describes the project and construction of a differential calorimeter designed to evaluate the heating generated by ultrasound beam in therapeutic levels. The calorimeter consists of two identical aluminum cylindrical chambers (for measurement and reference) filled with biological tissue mimicking material (phantom). Each chamber is fitted with six thermocouples type E (0.24 mm diameter) disposed along the wave propagation central axis, between the depths of 10-60 mm, distant 10 mm from each other. The power curve and the value of the effective radiation area (ERA) of the two transducers were estimated. From these data, the effective intensity was determined. The calorimeter was tested by using an ultrasound equipment of Physiotherapy, operating at the frequencies 1 and 3 MHz, continuous mode, nominal intensities 0.5, 1.0, 1.5 and 2.0 W.cm-2 and irradiation time 180 seconds. A sequence of eight protocols of measurement was repeated 10 times. At both frequencies, there was a decline of heating along the depth and the phantom region that heated the most corresponded to 10 mm of depth, in all intensities employed. The greatest increase in temperature occurred after application of 2.0 W.cm-2, with averages of 6.7 ± 1.0 oC and 12.6 ± 1.2 oC, at 1 MHz and 3 MHz, respectively. The proposed calorimeter may be useful for identifying possible local temperature maxima (hot spots) that appear along the central axis beam.

Carbon Nanotubes Cathode of Field Emission Lamp Prepared by Electrophoretic Deposition

Field emission lamp is a kind of green and low energy loss light source. Carbon nanotube cathode of field emission lamp was prepared by electrophoretic deposition. Two types of solute salt were added in electrophoretic solution separately, which were used to prepare two types of carbon nanotubes films on identical aluminum sheets by electrophoretic deposition method. Scanning electron microscopy(SEM) were used to observe the surface morphology of the films. The field emission properties of the films were tested by using a diode structure. The turn-on field of the film deposited with CsNO3 / Ca(NO3)2 4H2O solution was 0.7V/μm. The current density of the film was about 4000mA/cm2 at an electric field of 1.8V/μm. While corresponding data by using Mg(NO3)2 6H2O solution was 0.8V/μm and 3800mA/cm2. It is concluded that the field emission properties of the deposited film cathode by using CsNO3/ Ca(NO3)2 4H2O solution better than that using Mg(NO3)2 6H2O solution.

The Hotplate Precipitation Gauge

Abstract A new instrument designed to measure precipitation, the “hotplate precipitation gauge,” is described. The instrument consists of a heated thin disk that provides a reliable, low-maintenance method to measure precipitation rate every minute without the use of a wind shield. The disk consists of two heated, thermally isolated identical aluminum plates—one facing upward and the other downward. The two plates are heated independently, and both are maintained at constant temperature above 75°C by electronic circuitry that heats the plates depending on the deviation from the set temperature. Precipitation rate is estimated by calculating the power required to either melt or evaporate snow or to evaporate rain on the upward-facing plate, compensated for wind effects by subtracting out the power on the lower, downward-facing plate. Data from the World Meteorological Organization reference standard for liquid-equivalent snowfall rate measurements, the Double Fence Intercomparison Reference (DFIR) shield system, were used as the truth to develop the hotplate algorithm. The hotplate measures the liquid-equivalent precipitation rate from 0.25 to 35 mm h−1 within the National Weather Service standard for solid precipitation measurement. The hotplate was also shown to measure wind speed during severe icing conditions and during vibration. The high update rate (precipitation rate, wind speed, and temperature every 1 min), make this an ideal gauge for real-time applications, such as aircraft deicing and road weather conditions. It serves as an accumulation gauge by integrating the 1-min rates over time. It can also be used as a rain gauge for rainfall rates up to 35 mm h−1.

Mapping corrosion of metallic slab by thermography

Thermography is used to detect corrosion on a aluminum specimen. Two identical aluminum plates are extracted from the same base material. One of them is machined on one side, in such a way to simulate a material loss. Both the sound and damaged plate are heated on the undamaged side by a sine modulated heating source. A thermographic camera records a sequence of images of the temperature surface of both the sound and damaged sample on the heated (undamaged) sides. Several sequences are recorded with different modulation periods. By a suitable data reduction procedure, the thermographic sequence is reduced to a couple of images representing amplitude and phase of the oscillating temperature field. A perturbative method is used to solve iteratively the direct problem in the corroded domain that is confronted with the experimental data until an optimum matching is reached.

Design and Experimental Realization of a Broadband Transformation Media Field Rotator at Microwave Frequencies

We designed a metamaterial field rotator that can rotate electromagnetic wave fronts. Our starting point was the transformation-media concept. Effective medium theories and full simulations facilitated the actual design process. We created at a very simple structure comprising of an array of identical aluminum metal plates. We made and measured a sample and we experimentally demonstrated the field rotation effect as well as the broadband functionality at microwave frequencies.

Bending waves and pressure waves in solid rods.

Dimensionally identical aluminum rods are excited by a hammer impulse. One rod is suspended by rubber bands at a distance of nearly 1/4 of the length of the rod near the rod’s ends. The rod is excited near the end in a direction perpendicular to the rod axis. The other rod is supported by a clamp at the middle of the rod. This rod is excited by an impulse on the rod’s end face in the direction along the rod’s axis. In the first case the standing bending wave has a wavelength of nearly the length of the rod. In the second case the length of the standing wave is nearly twice the length of the rod. The resulting pitches observed clearly indicate that the propagation speed of the longitudinal wave by far exceeds the propagation speed of the transverse wave.

Structural assessment of van trailer floor systems with aluminium frame and wood decking

This paper studies the structural performance of two trailer floor systems with identical aluminium frames but different wood decking materials (solid hardwood planks and wood composite panels) when the floor systems are subjected to the forklift wheel loads. Finite element models were developed to simulate the floor response and full-scale static and cyclic loading tests were conducted. To improve the performance of the floor system with wood composite decking, modification of floor configuration was attempted and finite element modelling results predicted higher floor stiffness and load-carrying capacity.

Enhanced energy coupling and x-ray emission in Z-pinch plasma implosions

Recent experiments conducted on the Saturn pulsed-power generator at Sandia National Laboratories [R. B. Spielman et al., in Proceedings of the Second International Conference on Dense Z Pinches, Laguna Beach, CA, 1989, edited by N. R. Pereira, J. Davis, and N. Rostoker (American Institute of Physics, New York, 1989), p. 3] have produced large amounts of x-ray output, which cannot be accounted for in conventional magnetohydrodynamic (MHD) calculations. In these experiments, the Saturn current had a rise time of ∼180 ns in contrast to a rise time of ∼60 ns in Saturn’s earlier mode of operation. In both aluminum and tungsten wire-array Z-pinch implosions, 2–4 times more x-ray output was generated than could be supplied according to one-dimensional (1D) magnetohydrodynamic calculations by the combined action of the j×B acceleration forces and ohmic heating (as described by a classical Braginskii resistivity). In this paper, we reexamine the problem of coupling transmission line circuits to plasma fluid equations and derive expressions for the Z-pinch load circuit resistance and inductance that relate these quantities in a 1D analysis to the surface resistivity of the fluid, and to the magnetic field energy that is stored in the vacuum diode, respectively. Enhanced energy coupling in this analysis, therefore, comes from enhancements to the surface resistivity, and we show that plasma resistivities approximately three orders of magnitude larger than classical are needed in order to achieve energy inputs that are comparable to the Saturn experiment x-ray outputs. Large enhancements of the plasma resistivity increase the rate of magnetic field and current diffusion, significantly modify the qualitative features of the MHD, and raise important questions as to how the plasma fluid dynamics converts enhanced energy inputs into enhanced x-ray outputs. One-dimensional MHD calculations in which resistivity values are adjusted phenomenologically are used to illustrate how various dynamical assumptions influence the way enhanced energy inputs are channeled by the fluid dynamics. Variations in the parameters of the phenomenological model are made in order to determine how sensitively they influence the dynamics and the degree to which the calculated x-ray outputs can be made to replicate the kinds of large variations in the experimental x-ray power data that were observed in three nominally identical aluminum wire shots on Saturn.

Acoustic scattering by a pair of poroelastic spheres

An exact analysis for sound scattering by two interacting fluid-saturated porous-elastic spheres that are insonified by plane waves at arbitrary angles of incidence is outlined. The novel features of the Biot dynamic model for description of poroelastic material behaviour along with the appropriate wave field expansions, the pertinent boundary conditions, and the translational addition theorem for spherical wave functions are employed to develop a closed-form solution in the form of infinite series. The prime objective is to investigate the dynamic poroelasticity effects on acoustic scattering and its associated field quantities. The analytical results are illustrated with a numerical example in which two identical water-saturated aluminium foam spheres are insonified by a plane wave at broadside and end-on incidence. The basic acoustic field quantities, such as the form function amplitude and the scattered far-field pressure directivity pattern, are evaluated and discussed for representative values of the parameters characterizing the system. The effects of incident wave frequency, angle of incidence, and the proximity of the two spheres are examined. Limiting cases involving two rigid as well as two elastic spheres are considered and fair agreements with well-known solutions are established.

Electron energy device for process control

The electron energy is one of the principal parameters that influence the dose distribution within a product treated with a beam of energetic electrons. An easy-to-use and robust device has been developed that can reliably detect day-to-day small variations in the beam energy. It consists of two identical aluminium plates except for their thickness, which are electrically insulated from each other. The thickness of each plate is carefully selected depending on the electron-beam energy. The charge (or current) collected by each plate, while under the beam, is measured by an electrometer. The ratio of the charge (or current) signal from the front plate to the sum of the signals from the front and rear plates is very sensitive to the beam energy. We have used this device with an accelerator with maximum beam energy of 12 MeV. The high sensitivity and robustness make this device quite suitable for process control applications at an e-beam radiation-processing facility.

A comparison of the crashworthiness performance of geometrically identical aluminium and magnesium steering wheel armatures

This research deals with experimental impact testing and crashworthiness evaluation of geometrically identical aluminium and magnesium alloy steering wheel armatures. The aluminium wheel was made of a proprietary alloy developed by K S Centoco Ltd. and has a high degree of ductility and the magnesium wheel was made of an alloy from the AM50A magnesium alloy series. The approximate weight reduction achievable by employing the AM50A alloy is 2.98 N (or a 0.304 kg mass reduction). Sixteen different testing conditions were investigated which considered variations in the impact velocity of a rigid plate and the location of impact on the steering wheel armature. A crashworthiness analysis of the experimental results has shown that the aluminium armature has a higher amount of energy absorption than the magnesium armature with approximately equal peak impact loads. The deflections associated with the impact tests are larger for the magnesium armature. The elastic energy response for the magnesium armature is significantly higher than that of the aluminium armature and the aluminium armature is less sensitive to changes in the energy absorption factor for all the testing conditions considered in this study.

A comparison of the crashworthiness performance of geometrically identical aluminium and magnesium steering wheel armatures

A comparison of the crashworthiness performance of geometrically identical aluminium and magnesium steering wheel armatures

Wave impedances of drill strings and other periodic media.

It is commonly known that wave reflections are caused by abrupt spatial variations in the physical parameter called wave impedance. When a material contains a spatially periodic distribution of wave impedances some very interesting and complex wave propagation phenomena will occur. Two examples of such periodic structures immediately come to mind: the first is a sandwiched structure of two types of plates, say for example, identical layers of thin steel plates interspersed with identical thick aluminum plates; and the second is a large number of identical long thin pipes that are connected from end to end with identical short heavy threaded couplings. The pipe assembly is our primary concern here because it represents the drill string, used worldwide to drill for natural energy resources. We want to understand how waves propagate through drill strings because we want to use them as a means of communication. But while the second structure is our primary concern, it is the study of the first structure, composed of layers, that is the truly historical problem and the source of much of our understanding of this rich set of wave physics. Traditionally, wave propagation in periodic media has been studied as an eigenvalue problem. The eigenvalues themselves yield information about phase velocities, group velocities, passbands, and stopbands. Most often the analysis has stopped there and the eigenvectors have been ignored. Here we turn our attention to the eigenvectors, using them to evaluate the impedance of the periodic structure with particular emphasis on the periodic drill string. As you might expect the impedance of the drill string is a complex number, which is evaluated from a very complicated expression. However, we have discovered that the impedance at two physical locations along the length of each piece of drill pipe in the drill string always reduces to a real number. This is immensely important because it allows us to match the impedance of the drill string to our communication devices. We show how this leads to the effective design of repeaters, noise cancelers, wave terminators, and quarter-wave transformers for a drill-string communication system.

Nondestructive Evaluation of One-Dimensional Periodic Structures by Transmission of Laser-Excited Wide-Band Acoustic Pulses

The propagation of ultrasound in a one-dimensional model and actual periodic structures (PSs) is studied experimentally by the method of optoacoustic spectroscopy based on the laser thermooptical excitation and wide-band piezodetection of short acoustic pulses. It is shown that the ultrasound transmission spectrum of a PS has stop and pass bands, and the greater the number of layers in the PSs, the deeper the stop bands. The case where the thickness, density, and ultrasound velocity of one or several layers in the PS are modified is studied in detail. In this case, a narrow local maximum of ultrasound transmission appears in the stop band, whose location depends considerably on the position of the “defective” layer in the PS. The experimental data obtained coincide well with the theoretical calculation. The nondestructive evaluation of actual PSs consisting of two epoxy-glued identical aluminum plates is carried out by the optoacoustic method. Such materials are widely used in aircraft industry. It is shown that the ultrasound transmission spectrum for these materials depends considerably on the thickness of the epoxy-glue layer.

Spectroscopic Investigations and Molecular Dynamics Studies of Cationic Exchanged EMT Zeolites

Significant Raman and infrared spectra of the fully dehydrated and bare hexagonal M20EMT zeolites (M = Li+, Na+, K+, Rb+, Cs+, NH4+, and H+) have been obtained particularly in the low-frequency region, at room and low temperature. The vibrational properties of M20EMT were found to be analogous to those of cubic M40FAU with identical aluminum content. However, significant changes in position and intensity of the bands assigned to the framework vibrations were observed according to the nature of the extraframework charge-balancing cation of the exchanged zeolites. Molecular dynamics calculations were used to model the vibrational features of the MnEMT (n = 0 or 20; M = Na+ or K+) framework and extraframework cations. The main features of both the IR and Raman spectra were reproduced in the mid as well as in the low-frequency ranges. The results of the calculations demonstrate that the cation vibrations significantly participate in the spectral range from 20 to 250 cm-1 for all cation sites and are in accura...

A solution for the contact between two spherical particles undergoing large deformation

A unit model consisting of two particles in contact and under compression, leading to the development of an internal state variable (ISV) constitutive model incorporating the particle-to-particle contact during large deformations, is studied. Following Matthews' approximation that a general form of the Hertz elastic contact solution holds for nonlinear materials, an analytical solution based on the ISV constitutive model and valid for the small contact stage is first derived for the unit problem. To account for large contact areas, the analytical solution is modified based on numerical results obtained from a detailed finite element analysis of the compression of two identical spherical aluminum particles in contact. A set of unified relations is derived from this analysis that accounts for the strain rate effects and accurately represents the particle-to-particle contact behavior for both small and large contact areas. The performance of the proposed model is validated through comparisons with detailed numerical results obtained for a wide range of strain rates.