Identical Aluminum Research Articles

A dumbbell-shaped 3D flat plate pulsating heat pipe module augmented by capillarity gradient for high-power server CPU onsite cooling

With the development of the data center industry and the increasing power density of servers, it is crucial to remove waste heat from small-area heat sources to ensure the safe and efficient operation of data processing chips. To complement existing studies, in this paper, a novel three-dimensional flat plate aluminum pulsating heat pipe (3D-FPPHP) with four different channel structures for radial heat dissipation of high-power server chips was proposed. The results showed that under the favorable influence of the additional capillarity force provided by the variable diameter channels, the FPPHP filled with acetone can start up easily and has good robustness during variable power operation. When the input power was 150 W, the junction temperature of the heating source could be reduced by 42.49 °C (48.67%) compared to an identical aluminum plate. In addition, a heat sink module based on the proposed 3D-FPPHP with optimal charging ratio was tested in a 1U server chassis. The results showed that it can manage an input power of 300 W (corresponding to a heat flux of 41.15 W/cm2) and achieve a total thermal resistance of 0.2053 °C/W under the premise of ensuring a safe junction temperature of chips below 85 °C.

Ro-vibrational Spectrum of Linear Dialuminum Monoxide (Al2O) at 10 μm.

Dialuminum monoxide, Al2O, has been investigated in the laboratory at mid-IR wavelengths around 10 μm at high spectral resolution. The molecule was produced by laser ablation of an aluminum target with the addition of gaseous nitrous oxide, N2O. Subsequent adiabatic cooling of the gas in a supersonic beam expansion led to rotationally cold spectra. In total, 848 ro-vibrational transitions have been assigned to the fundamental asymmetric stretching mode ν3 and to five of its hot bands, originating from excited levels of the ν1 symmetric stretching mode and the ν2 bending mode. The measurements encompass 11 vibrational energy states (v1 v2l v3). The ro-vibrational transitions show spin statistical line intensity alternation of 7:5, which is caused by two identical aluminum nuclei of spin I = 5/2 at both ends of the centrosymmetric molecule of structure Al-O-Al. The less effective cooling of vibrational states in the supersonic beam expansion allowed measurement of transitions in excited vibrational states at energies of 1000 cm-1 and higher, while rotational levels within vibrational modes exhibited thermal population, with rotational temperatures around Trot = 115 K. Molecular parameters for 11 vibrational states were derived, including rotation and centrifugal distortion constants and l-type doubling constants for the states (v1 v2l v3) = (0 11 0) and (0 11 1) and an l-type resonance between the states (0 20 0) - (0 22 0) and (0 20 1) - (0 22 1). From the experimental results, rotational correction terms and the equilibrium bond length re were derived. The measurements were supported and guided by high-level quantum-chemical calculations that agree well with the derived experimental results.

In situ measurement of cavitation damage from single bubble collapse using high-speed chronoamperometry.

We quantitatively study cavitation damage non-invasively, in-place and time-resolved at microsecond resolution. A single, laser-induced bubble is generated in an aqueous NaCl solution close to the surface of an aluminum sample. High-speed chronoamperometry is used to record the corrosion current flowing between the sample and an identical aluminum electrode immersed in the same solution. This configuration makes it possible to measure the cavitation damage in the nanometer thin passive layer of the aluminum surface via the corrosion current from the repassivation. Synchronously with the corrosion current, the bubble dynamics is recorded via high-speed imaging. Correlation between the two measurements allows contributing cavitation damage to the respective stages of the bubble dynamics. The largest cavitation-induced currents were observed for the smallest initial bubble-to-surface stand-off distances. As the bubble re-expands and collapses again in several stages, further current peaks were detected implying a sequence of smaller damage. At intermediate stand-offs the bubble was not damaging and at large stand-off distances, the bubble was only damaging during the second collapse which again occurs at the solid surface.

Parameter Estimation and Application of Anisotropic Yield Criteria for Cylindrical Aluminum Extrusions: Theoretical Developments and StereoDIC Measurements

Theoretical and experimental studies are presented to characterize the anisotropic plastic response under torsion loading of two nominally identical aluminum Al6061-T6 extruded round bars. Theoretical models are developed using isotropic (Von Mises 1913) and anisotropic (Barlat 1991) yield criteria, along with isotropic strain hardening formulae, to model post-yield behavior under simple torsion loading. For the case of simple shear loading, incremental plasticity theory is used to determine the theoretical elastic, plastic, and total shear strains. A set of experiments are performed to calibrate Barlat’s 1991 yield function. Several specimens are extracted at different orientations to the longitudinal direction of each round Al6061-T6 bar and tested under uniaxial tension and simple torsion to optimally determine all anisotropic (Barlat 1991) yield function parameters. During loading, Stereo Digital Image Correlation (DIC) is used to quantify surface deformations for the torsion experiments and a baseline tension specimen to identify and correct measurement anomalies. Results show the isotropic yield model either underestimates or overestimates the experimental shear strains for both extrusions. Conversely, results using the Barlat 1991 anisotropic yield criteria are in excellent agreement with experimental measurements for both extrusions. The presence of significant differences in the anisotropic parameters for nominally similar extrusions confirms that plastic anisotropy is essential for the accurate prediction of mechanical behavior in longitudinally extruded Al6061-T6 bars.

Comprehensive analysis of the coated component from a FORD engine

The article is devoted to a comprehensive analysis of the coating of a component from the Ford Fo-cus 1.0 l EcoBoost engine. It is one of a pair of materially identical aluminum gears connected by a drive pulley and a drive. Aluminum gear components are surface treated with a mixture of metal powders using PVD technology, where the goal of the coating is to increase the hardness, abrasion resistance and heat of the base material. The chemical composition of the basic material of the gea-red aluminum drive wheel of the FORD engine proves that it is a component made by thermofor-ming and corresponds to the alloy EN AW 6061 (AlMg1SiCu) according to the standard ČSN EN 573 1-3. The microstructure of the base material component exhibits fine intermetallic phases evenly dis-tributed throughout the cross-section of the base base material, without the occurrence of larger inc-lusions and/or porosity. The cross-sectional microstructure in the area of the coating demonstrates that the component has a continuous uniform surface layer of the coating formed without a defect and does not have a diffuse bond with the base material. The measurement of the coating thickness of the component shows a continuous surface layer formed by powder metallography, which ranges from 70.1 µm to 143.9 µm. The surface EDS of the surface proves that it consists of deposited tungsten carbides produced by powder metallography and the bonding material is cobalt. Area EDS analysis of the surface coating identified morphologically two distinct areas of dark and light, where tungsten carbides and cobalt are based, and only the tungsten carbide and cobalt carbide contents change. The oxygen and carbon content also changes in the dark and light areas.

On the Energy Absorption Capability of Metallic Tubes Subjected to the Radial Wall Crushing Process

Metallic tubes, under axial loading, are frequently preferred in many different industries due to their high energy absorption efficiency. The studies to increase the energy absorption capacity (EAC) of these structures are still up to date. In this study, the deformation behavior and EAC of regionally pre-deformed identical aluminum and steel tubes under axial loading were investigated experimentally. Regional strength increase in tubes was obtained by the radial wall crushing (RWC) process. The RWC process is carried out by radially crushing the desired areas of the metallic tube from the outside with the aid of a specially designed device. Strengthening (hardening) occurs in the pre-deformed regions and as a result, the EAC of the metallic tubes can be increased. It is also noteworthy that the increase in absorbed energy is provided without reinforcement materials. When the experimental results were examined, it was seen that the RWC increased the energy absorption value of aluminum and steel tubes approximately 23% and by 33%, respectively. In addition to energy increases, the folding beginning of the metallic tubes can also be directed by using the RWC process.

High-velocity impact response of fiber metal laminates: Experimental investigation of projectile's deformability

The aim of this research is to investigate the influence of projectile's deformability on ballistic impact response of fiber metal laminates. High-velocity impact experiments have been carried out via a light gas gun setup using rigid, semi-rigid and deformable projectiles with the same diameter, nose shape and mass. Fiber metal laminates have been made of two identical aluminum facing plates and different number of glass/epoxy composite plies in the middle. Several local and global mechanisms for kinetic energy absorption of projectiles have been detailed and ballistic limit velocity, as well as specific perforating energy for all cases have been determined. The results indicated that by increasing the deformability of the projectile, the amount of local and global wasting energy mechanisms for dissipating the velocity of projectiles have been increased. Furthermore, the interaction between non-rigid projectiles and fiber metal laminate targets as well as permanent deformation of non-rigid projectiles, had important effects on preventing the projectile penetration. By increasing the deformability of projectiles and/or increasing the number of composite plies, permanent deformation of facing plates, fiber breakage, crushing as well as delamination and debonding have been increased and local damage modes in facing plates changed from petalling to plugging. Besides, rigid projectiles possessed less specific perforating energy compared with deformable projectiles and required minimum initial velocity for full penetration.

Microchannel Thermal Management System With Two-Phase Flow for Power Electronics Over 500 W/cm2 Heat Dissipation

In this article, a microchannel thermal management system (MTMS) with the two-phase flow using the refrigerant R1234yf with low global warming potential is presented. The thermal test vehicles (TTVs) were made of either single or multiple thermal test chips embedded in the substrates, which were then attached to the MTMS. The system included two identical aluminum microchannel heat sinks (MHSs) connected in series in the cooling loop, which also consisted of a gas flowmeter, a miniature compressor, a condenser, a throttling device, and accessory measurement components. The experimental results showed that the thermal management system could dissipate a heat flux of 526 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> while maintaining the junction temperature below 120 °C. For SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> with a higher junction temperature, e.g., 175 °C, the current system is expected to dissipate a heat flux as high as about 750 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The effects of the rotational speed of the compressor, the opening of the throttling device, TTV layout on MHS, and a downstream heater on the cooling performance of the system were analyzed in detail. The study shows that the present thermal management with a two-phase flow system is a promising cooling technology for the high heat flux SiC devices.

Experimental and numerical study on energy absorption performance of CFRP/aluminum hybrid square tubes under axial loading

Metal/composite hybrid square tubes that combine the advantages of low-density of composite with low-cost of metal provide a potential energy absorption device for automobiles. The axial crushing performance of CFRP/aluminum hybrid square tubes wrapped with single angle-ply and antisymmetric angle-ply was studied by experimental and numerical methods. Results show that for tubes wrapped with single angle-ply [0]4 or [45]4, crack propagation occurred and the CFRP separated from aluminum, which resulted in worse energy absorption capacity than pure aluminum tube. A stable symmetric deformation was observed in hybrid square tubes wrapped with antisymmetric angle-ply. The specific energy absorption (SEA) for those tubes was improved 11% and they showed better energy absorption performance compared to pure aluminum tube. Then, the effect of thickness of tubes, including hybrid square tubes with identical aluminum and hybrid square tubes with identical mass, on the energy absorption capacity was further investigated by simulation. It was found that only when the number of CFRP layer reaches a certain value, hybrid square tubes perform better than pure aluminum tube with identical mass in energy absorption. Moreover, influence of mass of the tube, and substituting aluminum alloy with CFRP on the energy absorption of hybrid square tubes with identical aluminum and different number of CFRP layers was studied.

Quasi-Static Axial Compression Behavior and Energy Absorption Evaluation of Steel Foam-Filled Tubes

The aim of this paper is to study the quasi-static axial compressive performance of newly developed steel foam-filled tubes (SFFTs). The energy absorption capability of steel foam-filled tubes was assessed. The results show that steel foam-filled tubes collapse in the axisymmetric-concertina deformation mode. The plateau stress of the plastic deformation of the steel foam-filled tubes decreases with the increase of porosity of steel foams, and is significantly higher than the sum of the identical steel foam and aluminum tube. The absorbed energy per unit volume of the steel foam-filled tubes is 8%~ 15% higher than the sum of those of identical aluminum tubes and steel foams with porosity ranging from 65% to 80%.

Low Power RF Test of a Quadrupole-free X-Band Mode Launcher for High Brightness Applications

In this work we present the low power RF characterization of a novel TM01 X-band mode launcher for the new generation of high brightness RF photo-injectors. The proposed mode launcher exploits a fourfold symmetry which minimizes both the dipole and the quadrupole fields in order to mitigate the emittance growth in the early stages of the acceleration process. Two identical aluminum mode launchers have been assembled and measured in back-to-back configurations for three different central waveguide lengths. From the back-to-back results we infer the performance of each mode launcher. The low power RF test, performed at the Istituto Nazionale di Fisica Nucleare Laboratori Nazionali del Sud (INFN-LNS), validate both the numerical simulations and the quality of fabrication. An oxygen-free high-conductivity copper version of the device is being manufactured for high power and ultra high vacuum tests that are planned to be conducted at SLAC.

On the Potential Static Strength of Hybrid (Bolted/Bonded) Lap Joints with Functionally Graded Adhesives

In this paper, the potential static strength of hybrid (bolted/bonded)—termed “HBB”—joints with functionally graded adhesives (FGA) is theoretically investigated, in reference to the pure bolted joint, the pure bonded joint, and the HBB joint with homogeneous adhesive (HA). The investigation is performed on a particular in-plane tensile-loaded single-lap joint made of identical aluminum adherends with two lines of fasteners and three various adhesive symmetrical graduation laws. The stress analysis is performed using the macro-element technique within 1D-bar framework. Moreover, closed-form expressions for the bolt load transfer rates and maximal adhesive stresses of balanced single-lap HBB joint with two identical fasteners are derived. It is shown that the FGAs allow fort a better load sharing between the adhesive and the fasteners than the HA. Moreover, the use of FGAs instead of HA could lead to a potential static strength benefit for the adhesive layer part rather than for the fastening part.

ANALYSIS OF THE REGULATORY FRAMEWORK AND METHODOLOGICAL PROBLEMS OF HOUSEHOLD FOIL TESTING WITH REGARD TO THE AMOUNT OF ALUMINUM MIGRATION INTO FOOD PRODUCTS

The paper shows that the technical regulation of the Russian Federation regarding the safety of aluminum foil for consumer health has a number of methodological problems. We studied the laboratory test reports and found the reasons that could cause the lack of reproducibility of the studies’ results for a number of identical aluminum foil samples. A number of differences were identified in domestic and foreign regulatory and procedural documents on the evaluation of household foil testing with regard to the amount of aluminum migration from packaging materials into food products. It is necessary to clarify the methods for sanitary-chemical research of products in contact with food. It is proposed to conduct a detailed study of the conformity of specific model media to certain food products and make changes and additions to regulatory and methodical instruments as a result.

A generalizable deep learning framework for localizing and characterizing acoustic emission sources in riveted metallic panels

Abstract This paper introduces a deep learning-based framework to localize and characterize acoustic emission (AE) sources in plate-like structures that have complex geometric features, such as doublers and rivet connections. Specifically, stacked autoencoders are pre-trained and utilized in a two-step approach that first localizes AE sources and then characterizes them. To achieve these tasks with only one AE sensor, the paper leverages the reverberation patterns, multimodal characteristics, and dispersive behavior of AE waveforms. The considered waveforms include AE sources near rivet connections, on the surface of the plate-like structure, and on its edges. After identifying AE sources that occur near rivet connections, the proposed framework classifies them into four source-to-rivet distance categories. In addition, the paper investigates the sensitivity of localization results to the number of sensors and compares their localization accuracy with the triangulation method as well as machine learning algorithms, including support vector machine (SVM) and shallow neural network. Moreover, the generalization of the deep learning approach is evaluated for typical scenarios in which the training and testing conditions are not identical. To train and test the performance of the proposed approach, Hsu-Nielsen pencil lead break tests were carried out on two identical aluminum panels with a riveted stiffener. The results demonstrate the effectiveness of the deep learning-based framework for single-sensor, AE-based structural health monitoring of plate-like structures.

Stress wave propagation in a functionally graded adhesive layer between two identical cylinders

ABSTRACTThis study investigates the stress wave propagation in circular aluminum cylinders bonded with a functionally graded adhesive layer subjected to an axial impulsive load. The adhesive joint consists of two identical (aluminum) cylinders and a functionally graded adhesive layer. The volume fractions of the two constituents: aluminum and epoxy in the adhesive layer were functionally tailored through the adhesive thickness by obeying a power-law. Therefore, the effective material properties at any point in the adhesive layer were predicted by the Mori-Tanaka homogenization scheme. The governing equations of the wave propagation in the joint were discretized by means of the finite difference method. The influence of the compositional gradient exponent on the displacement and stress distributions of the joint was examined. It was observed that changing the material composition of the adhesive layer had an evident effect on the displacement and stress levels, especially in the lower cylinder. On the contrary, the influence of the compositional gradient exponent was found to be minor on the displacement and stress distributions. The displacement and stress distributions were also investigated along the upper and lower cylinder-adhesive interfaces. Accordingly, with increasing the ductility of the adhesive layer the waves transmitted to the lower cylinder caused lower displacement levels. The normal stresses become peak at the bottom corners of the upper and lower cylinder-adhesive interfaces whereas the shear stresses concentrate in the middle region of the interfaces. In addition, the temporal variations of the displacement and stress components were evaluated at some critical points of the adhesive and lower cylinder. The compositional gradient exponent played an important role on the displacement and stress levels as well as the wave speeds in the adhesive and lower cylinder rather than in the upper cylinder. The stresses in the joints were observed to be alleviated by employing a functionally graded adhesive layer.

Experimental validation of mathematical models of identical aluminum and stainless steel engineered conical solar collectors

This paper studies the mathematical modeling of a conical solar collector (CSC) based on different reflector materials and view angles. The optical performance testing using both stainless steel reflector (SSR) and aluminum mirror reflector (AMR) was performed under similar conditions at reflector view angles of 35°, 40°, and 45°, respectively. Main operational parameters related to the thermal/optical efficiencies of the SSR and AMR systems were determined and compared with each other. In addition, the interdependent transient temperature responses of both system components were predicted using Matlab® ordinary differential equation (ODE) solvers. For the purpose of model validation, simulation results from both systems were compared with experimental data. Results showed that the highest efficiencies and maximum water temperatures were achieved at reflector view angle of 45°, but these values were significantly higher in AMR system than SSR system for all of the aforementioned cases.

Observation of pH Value in Electrokinetic Remediation using various electrolyte (MgSO4, KH2PO4 and Na(NO3)) for Barren Acidic Soil at Ayer Hitam, Johor, Malaysia

Barren acidic soil collected at Ayer Hitam, Johor Malaysia was recorded at pH value of 2.36 with relative humidity of 86%. This pH value is not suitable for the growth of any plants especially for the soil stabilization purposes. Gradation weathering within the range of 4 to 6 indicates an incomplete/partial weathering process. The soil grade in this range is known as a black shale mudstone. Beside, this also influences to a factor of the high surface water runoff at this particular soil species. As the acidic pH become a major problem for soil fertilizing hence an appropriate technique was implemented known as using ‘Electrokinetic Remediation’, EKR. This technique has a great potential in changing the soil pH value from acidic to less acidic and also kept maintain the pH at the saturated rate of electrochemical process. This research study presents the monitoring data of pH value due to the effect of various electrolyte consist of 0.5M of MgSO4, KH2PO4, and Na(NO3). Here, the distilled water (DW) was used as reference solution. The electric field was provided by dipping two pieces of identical rectangular aluminum foil as anode and cathode. The EKR was conducted under a constant voltage gradient of 50 V/m across the sample bulk at 0.14 m length measured between both electrodes. The data collection was conducted during the total period of 7 days surveillance. The variation of pH values at the remediation area between anode and cathode for various type of electrolyte indicates that there are a significant saturated value as it reaches 7 days of treatment. During the analysis, it is found that the highest pH value at the remediation area after 7 days treatment using Na(NO3), KH2PO4 and MgSO4 was 3.93, 3.33 and 3.39 respectively. Hence from the last stage of pH value observation, it can be conclude that the best electrolyte for barren soil treatment is Na(NO3) whereby it contribute to highest pH value and turn the soil to be less acidic.

Damage imaging using non-contact air-coupled transducer/laser Doppler vibrometer system

In this work, a rapid imaging technique is proposed for imaging damage in metallic plates using a zero-lag cross-correlation imaging condition in the frequency domain. A fully non-contact, single-side access, hybrid inspection system employing air-coupled transducer (ACT) for the generation of anti-symmetric Lamb wave mode and laser Doppler vibrometer (LDV) for dynamic visualization of the Lamb wavefield is used to experimentally verify the proposed technique on three identical aluminum plates with same notch geometry but with various orientations at different locations. The notches (10 mm × 5 mm) are grooved in the aluminum plates using electric discharge machining with a maximum depth of 40% of plate’s thickness and with the following orientations 90°, 60°, and 45° with respect to the horizontal axis. A damage image is constructed by cross-correlating the forward and backward propagating wavefields in the aluminum plates which are separated by analyzing the actual laser Doppler vibrometer measured wavefield using a frequency–wavenumber filtering post-processing technique. The experimental results demonstrate a strong capability of guided wave zero-lag cross-correlation imaging condition technique in localizing, sizing, and detecting the orientation of relatively small defects in the isotopic material.

Experimental Investigation of the Role of Large Scale Cavitating Vortical Structures in Performance Breakdown of an Axial Waterjet Pump

Flow phenomena and mechanisms involved in cavitation breakdown, namely, a severe degradation of pump performance caused by cavitation, have been a longstanding puzzle. In this paper, results of high-speed imaging as well as pressure and performance measurements are used to elucidate the specific mechanism involved with cavitation breakdown within an axial waterjet pump. The experiments have been performed using geometrically identical aluminum and transparent acrylic rotors, the latter allowing uninhibited visual access to the cavitation phenomena within the blade passage. The observations demonstrate that interaction between the tip leakage vortex (TLV) and trailing edge of the attached cavitation near the rotor blade tip that covers the suction side (SS) of the blade plays a key role in processes leading to breakdown. In particular, the vortical cloud cavitation developing at the trailing edge of the sheet cavity near the blade tip is entrained and re-oriented by the TLV in a direction that is nearly perpendicular to the blade SS surface, and then convected downstream through the blade passage. Well above breakdown cavitation indices, these “perpendicular cavitating vortices” or PCVs occur in the region where blades do not overlap, and they only affect the local flow complexity with minimal impact on the global pump performance. With decreasing pressure and growing sheet cavitation coverage of the blade surface, this interaction occurs in the region where two adjacent rotor blades overlap, and the PCV extends from the SS surface of the originating blade to the pressure side (PS) of the neighboring blade. Cavitation breakdown begins when the PCV extends between blades, effectively blocking the tip region of the rotor passage. With further decrease in pressure, the PCVs grow in size and strength, and extend deeper into the passage, causing rapid degradation in performance. Accordingly, the casing pressure measurements confirm that attachment of the PCV to the PS of the blade causes rapid decrease in the pressure difference across this blade, i.e., a rapid decrease in blade loading near the tip. Similar large perpendicular vortical structures have been observed in the heavily loaded cavitating rocket inducers (Acosta, 1958, “An Experimental Study of Cavitating Inducers,” Proceedings of the Second Symposium on Naval Hydrodynamics, ONR/ACR-38, pp. 537–557 and Tsujimoto, 2007, “Tip Leakage and Backflow Vortex Cavitation,” Fluid Dynamics of Cavitation and Cavitating Turbopumps, L. d'Agostino and M. Salvetti, eds., Springer, Vienna, Austria, pp. 231–251), where they extend far upstream of the rotor and cause global flow instabilities.

Development of numerical realistic model for predicting low-velocity impact response of aluminium honeycomb sandwich structures

This paper presents the results of an experimental and numerical study on aluminium honeycomb sandwich structures under low-velocity impact loadings. In order to investigate the impact behavior of honeycomb sandwich structures, which is consisted of two identical aluminium facesheets and an aluminium honeycomb core, an experimental study was carried out by using a drop-weight impact test system. Using this system, the contact forces and absorbed energies were measured to determine the influence of impact energy for one configuration of the sandwich structure. According to these results, a numerical model by finite element method of sandwich structures was developed, which is in good agreement with experimental results in terms of contact forces and deformations. Later, the effect of the cell size and the height variation of aluminum honeycomb core on the impact response of sandwich structures were investigated using the improved numerical model. The obtained numerical and experimental results were interpreted in detail.