Small Aluminum Research Articles

Informative Bayesian tools for damage localisation by decomposition of Lamb wave signals

Ultrasonic guided waves offer a convenient and practical approach to structural health monitoring and non-destructive evaluation, thanks to some distinct advantages. Guided waves, in particular Lamb waves, can be used to localise damage by utilising prior knowledge of propagation and reflection characteristics. Typical localisation methods make use of the time of arrival of waves emitted or reflected from the damage, the simplest of which involves triangulation (with a known wave speed). In order to obtain reflection information, it is useful to decompose the measured signal into the expected waves propagating directly from the actuation source in the absence of damage, called a baseline, and for this paper referred to as nominal waves. This decomposition allows for determination of the residual signal which contains only waves from reflection sources such as damage, boundaries or other local inhomogeneities. Previous decomposition methods make use of accurate analytical models, but there is a gap in methods of decomposition for complex materials and structures. A new method is shown here which uses a Bayesian approach to decompose single-source signals, requiring only prior information on surface displacement along the propagation path. This Bayesian decomposition has the advantage of generating a distribution of possible nominal signals and allows for quantification of the uncertainty of the expected signal. Furthermore, the approach produces inherent parametric features which correlate to known physics of guided waves, and likelihood estimates can be used to assess the quality of the decomposition. In this paper, the decomposition method is demonstrated on data from a simulation of guided wave propagation in a small aluminium plate, using the local interaction simulation approach, for a damaged and undamaged case. Analysis of the decomposition method is done in three ways; inspect individual decomposed signals, track the inherently produced parametric features along propagation distance, and use method in a localisation strategy. The localisation method is demonstrated using the decomposed signal at several sensor locations and triangulates for the source of reflected waves from damage. The Bayesian decomposition was found to work well in returning signals containing only reflected waves, as well as obtaining parametric features that can be used to assess damage and confidence in the decomposed wave. The use of these waves in the localisation method returned estimates accurate to within 1 mm in many sensor configurations. Leading on from the work shown here, the paper finishes with future work; the authors intend to extend this method to scenarios where less prior knowledge is available.

Numerical Analysis of Microstructure Anomalies during Laser Welding Nickel-Based Single-Crystal Superalloy Part I: Salient Aluminum Redistribution Melioration

Correlation between welding conditions, such as laser power, welding speed and welding configuration, microstructure anomalies, including columnar/equiaxed transition (CET) and stray grain formation, and metallurgical factors, such as aluminum redistribution and supersaturation near dendrite tip, is elucidated by thorough numerical analysis to explain prevalent phenomenon of insidious microstructure development and face the challenge of microstructure amelioration as well as solidification cracking resistance improvement during course of ternary single-crystal Nickel-Chromium-Aluminum superalloy melt-pool solidification for crack-free laser surface modification. Metallurgical factors of γ gamma phase microstructure development strongly depend on welding configuration, and heat input is not as important as welding configuration. Although melted-pool center region is susceptible to microstructure anomalies, (001)/[100] welding configuration possesses auspicious growth crystallography under which the bimodal profiles of solid aluminum concentration and liquid aluminum supersaturation ahead of dendrite tip are symmetrically distributed to potentially decrease solute redistribution and increase resistibility to solidification cracking. Dissimilarly, (001)/[110] welding configuration possesses insidious growth crystallography under which the profiles of solid aluminum concentration and liquid aluminum supersaturation ahead of dendrite tip are asymmetrically distributed to preferably facilitate alloying plentiful enrichment and differentiate problematical microstructure instability on half side of molten pool. In the bottom of molten pool, beneficial Al-barren [001] dendrite is kinetically driven by homologous single-crystal epitaxial growth without columnar/equiaxed transition. On the right side of molten pool, detrimental Al-rich [100] dendrite is spontaneously susceptible to stray grain formation with equiaxed morphology. Symmetrical microstructure development is more enrichment-resistant than asymmetrical microstructure development, which is crystallographically ascribable to favorable thermo-metallurgical factors, i.e. aluminum redistribution mitigation and supersaturation relief, and substantially reduce metallurgical degradation and microstructure failure. The faster welding speed and the lower laser power are used, the smaller aluminum concentration and supersaturation ahead of dendrite tip are kinetically incurred to suppress columnar/equiaxed transition and stray grain formation with a number of thermometallurgical factors contribution to considerable microstructure amelioration and increasingly improve solidification cracking resistance and vice versa. Shallow molten-pool shape with symmetrical growth crystallography efficiently advances anomalies-resistant microstructure development with diminution of partition driving forces for solute redistribution and supersaturation during nonequilibrium solidification instead of deep molten-pool shape with asymmetrical growth crystallography. The latter importantly aggravates stray grain formation. Useful combination of optimum solidification conditions and favorable growth crystallography predominantly minimizes diffusion-controlled solute deviation and microstructure anomalies for excellent single-crystal superalloy laser processing without cracking, and possesses tenable relationship between welding conditions, solute redistribution and microstructure anomalies. The mechanism of crystallography-aided concentration fluctuation and copious supersaturation behind prominent phenomenon of microstructure anomalies, where nucleation and growth of stray grain formation near dendrite tip are activated, is consequently proposed. The comparison between numerical analyses and experiment results are valid and satisfactory. Microstructure anomalies are predictable for proper understanding of multicomponent microstructure development in the interior of fusion zone. The theoretical methodology is reproducible as consequence of availability of thermodynamic and kinetic properties of Nickel-based or Iron-based single-crystal superalloys.

Laser-plasma jet driven sub-millimeter diameter aluminum flyer and its gesture diagnosis

Laser-driven flyer has been studied for decades as it promises to possess many applications such as in measuring the equation of state (EOS) under ultrahigh pressure, investigating the material dynamic properties under high strain rate, simulating the high-speed impact for aircraft protection, and igniting explosives. However, the planarity and integrity of flyers are determined by indirect velocity lnterferometer system for any reflector (VISAR) or witness slab results due to its high speed and small dimension. For further and wide applications, it is very important to obtain direct experimental proof of the flyer gesture and configuration. Thus, the acceleration and gesture investigation of aluminum flyer driven by laser plasma are studied on Xingguang-III laser facility. The X-ray radiography is achieved by a picosecond laser irradiating the copper wire target. The shadowgraph of flyer and plasma are realized by the incidence of a bunch of infrared laser through the flyer flight path. In additon, photon Doppler velocimetry is employed to measure the flyer velocity simultaneously. The radiography, shadowgraph and velocity of typical small aluminum flyer are obtained. By optimizing the thickness of both CH ablation layer and vacuum gap, the flyer is slowly accelerated via consecutive stress wave produced by plasma colliding. The aluminum flyer has a thickness of 20 μm and diameter of about 500 μm. The whole flyer remains the integrated shape after a great angle of rotation due to uneven plasma loading. The flight distance is about 400 μm, giving an average velocity of 2.2 km/s. The planarity of the flyer is good except a little bend on the two sides due to side rarefaction of plasma. The study verifies that the laser plasma collision can generate a sub-millimeter-diameter metal flyer with integrated shape and a velocity of several kilo-meters per second, showing that it possesses the promising applications in measuring the EOS and igniting explosive .

Development of an adaptive CTM–RPIM method for modeling large deformation problems in geotechnical engineering

In this paper, a meshfree method called adaptive CTM–RPIM is developed to model geotechnical problems with large deformation. The developed adaptive CTM–RPIM is a combination of the Cartesian transformation method (CTM), the radial point interpolation method (RPIM) and the alpha shape method. To reduce the requirement for meshes, the CTM is adopted to transform domain integrals into line integrals, and the RPIM is applied to construct interpolation functions. The alpha shape method, which is capable of capturing severe boundary evolution due to large deformations, is then introduced into the CTM–RPIM to form the adaptive CTM–RPIM. The accuracy of CTM–RPIM is first verified by considering a cantilever beam under small deformation, where the influence of key parameters on the simulation results is explored. Afterward, the ability of the adaptive CTM–RPIM to handle large deformation problems is demonstrated by simulating cantilever beams with large deformations for which analytical solutions are available. Finally, the ability of the proposed method to model the geotechnical large deformations is illustrated from both quasi-static and dynamic aspects, where a slope failure problem and a footing bearing capacity problem are modeled to evaluate the stability of geotechnical structures; and a 2-D soil collapse experiment using small aluminum bars is simulated to show the method capability in describing the soil flows. These benchmark examples demonstrate that the adaptive CTM–RPIM is a numerical method with broad application prospects for modeling large deformation problems in geotechnical engineering.

Electromagnetic attraction bulging of small aluminum alloy tube based on a field shaper

Electromagnetic attraction bulging of small aluminum alloy tube based on a field shaper

3D characterisation of debris clouds under hypervelocity impact with large-field pulsed digital in-line holography

To expand the field of view and obtain a full-scale image of a debris cloud, a large-field pulsed digital in-line holography (DIH) system is developed to study the three-dimensional (3D) positions and shapes of debris clouds generated by hypervelocity impact. A general model for the large-field pulsed DIH system is introduced. Derived from strict theoretical analysis, it suggests that the hologram recorded by a large-field pulsed DIH system can be described by an equivalent lensless system. At the Hypervelocity Impact Research Centre of the China Aerodynamics Research and Development Centre, based on hypervelocity impact equipment with a 7.6 mm bore, experiments on a 3 mm aluminium sphere impacting a 1 mm thick aluminium target plate with a velocity of 3.58 km/s were carried out. Ensuring the successful capture of the transient state of debris clouds, the large-field pulsed DIH system is synchronised with the impact event and the combination of the neutral density filter and the bandpass filter is proposed, to eliminate the plasma radiation and enhance the signal-to-noise ratio of the hologram. The experimental results show that the holographic fringes are clearly recorded and the detailed shapes and structures of both large and small aluminium fragments are observed after reconstruction. The structure of debris clouds can be divided into three parts: front, core and shell, agreeing well with results measured by laser shadowgraph. The study demonstrates the feasibility of a large-field pulsed DIH system for accurate measurements of ultrafast debris clouds and shows great potential in the diagnostics of hypervelocity impacts.

The Effect of using Compound Techniques (Passive and Active) on the Double Pipe Heat Exchanger Performance

This experimental study explores the effect of using compound technique (passive techniques (packing the shell side with small cylindrical aluminium pieces) and active techniques (air injection or bubble generation) were securitized. It is conducted for both configurations (parallel and counter) flow with applying both techniques (compound) at the same conditions in a double pipe heat exchanger. The main objective of this study is to indicate the effect of employing the two techniques simultaneously and compare the outcomes without and with the passive (packing) method under the same conditions. The heat transfer of heat exchanger in terms of cost and size has been For this purpose the test rig is prepared by designing and making a suitable heat exchanger equipped with flow meters and thermocouples for measuring flow rates and temperatures (Tin and Tout) of both fluids (hot and cold) . The hot fluid is heated in a small tank by electrical heater with temperature controller from (TEquipment). The results show that the performance parameters of the heat exchanger enhanced about (15%) for case of applying the both techniques together and (25)% for case of using active method only.

Effects of the Particle Size and Gas Environment on Afterburning Reactions and Explosion Performance of Aluminized HMX-Based Explosives

In this paper, confined explosions of HMX-based aluminized explosives in a spherical chamber are studied. The effects of aluminum particles on the afterburning reaction and explosive performance are obtained by changing the size of the particles and the gas environment. The results show that the concentration of oxygen in air is not sufficient to support complete combustion of aluminum particles. The estimated oxidation rate of aluminum particles is 87–93%, and it tends to decrease with increasing particle size. Part of aluminum particles oxidize with detonation products, and the reaction can last for hundreds of microseconds. However, the degree of oxidation between the large-sized aluminum particles and detonation products is small. A new method is used to estimate the initial energy of detonation by observing the time difference between sensing the initial light and the pressure wave. This method leads to a conclusion that some of the aluminum particles are oxidized during detonation and provide additional energy to the primary blast wave. Small micron-sized aluminum particles in the range of 48.9 nm to 46.7 $$\mu$$ m extend the duration of the fireball.

Implementação da Norma Regulamentadora NR-12 em uma máquina fundidora de peças de alumínio

<span class="fontstyle0">In the current political and economic environment that we live in Brazil, a conservative wave is in constant movement and has been modifying the social rights of workers, among them the risks exposed in the use of machines and equipment, guaranteed by Normative Resolution NR-12. This article aims to gather the technical methodology that aims to assist the decision making in the choice of actions for the adequacy of the NR-12 for its application in an aluminum casting machine. This work aims to assist the professional in the area of work safety engineering to have parameters of choice and application for the most diverse measures and possible actions regarding the mechanical and electrical devices to be used as protection of a small aluminum parts casting machine (machine object of study), guaranteeing the safety objectives in the operation of this equipment, based on the Literature review for the correct application of the legislation. In conclusion, the adaptations will be carried out in the equipment in a safe, dynamic and low cost way for the company and with the minimum possibility of rework, the application of the correct measurement and also the involvement of a multidisciplinary team with representatives of the maintenance, production and process.</span> <br /><br />

An experimental study of non-spinning stone-skipping process

The process of throwing a small aluminum circular disk toward the water surface to simulate the stone-skipping phenomenon is experimentally observed and analyzed in this paper. Four stages consisting of pre-hitting, hitting, sliding, and aft-sliding stages for a single skipping process are proposed for a thorough analysis and better understanding of the fundamental physical mechanism of the stone-skipping phenomenon. It is found through this study that, if spinning is not allowed, it is hardly possible to generate the stone-skipping phenomenon when the initial inclined angle of throwing is greater than 8°. Moreover, the maximum number of skips is less than that when spinning is allowed. For larger initial inclined angles of throwing, water walking with or without lateral roll are observed, which is quite different from the stone-skipping phenomena usually observed.

Twice-FFT demodulation for signal distortion in optical fiber FP acoustic sensor

A Twice-FFT demodulation method for signal distortion state is proposed and experimentally demonstrated in an optical fiber Fabry-Perot (FP) acoustic sensor. Here the fiber FP acoustic sensor element is build with fiber end face and combination of diaphragms which is composed of a small round aluminum foil and a polymer PET film. The hypotenuse intensity demodulation method is applied to acquire the acoustic signal in time domain assisted with a Photodetector (PD) and an oscilloscope. The first Fast Fourier transform (FFT) processing results show harmonic distortion on the frequency domain spectrum. To demodulate the acoustic frequency and amplitude information, twice-FFT processing is preformed. Experimental results reveal an accuracy up to 95.6% of acoustic signal in the frequency range 2–100 Hz. Our scheme provides a new option for signal demodulation of optical fiber acoustic sensors (OFAS).

Coagulation behaviors of aluminum salts towards humic acid: Detailed analysis of aluminum speciation and transformation

The hydrolysis of Al-based coagulants, especially aluminum speciation and transformation, is necessary for organic matter removal by the coagulation process. The goal of this study was to investigate the efficiency and mechanism of hydrolyzed Al species in the coagulation of humic acid (HA) removal. Three aluminum coagulants have been applied to investigate HA coagulation, which are aluminum chloride AlCl3 dominated by monomeric aluminum species Ala, polyaluminum chloride PACl1 dominated by medium polymer species Alb, and commercial polyaluminum chloride PACl2 dominated by larger polymer species and/or colloidal aluminum species Alc. Results showed that the best coagulation effect on HA removal (higher than 90%) occurred at pH 6 for three aluminum coagulants and their effect decreased in the order: PACl1 > AlCl3 > PACl2. Except that, the in situ hydrolyzed aluminum species produced by AlCl3 had synergistic effects on various sites of HA, and showed good adaptability to raw water and coagulant dosage. Hydrolyzed larger polymeric aluminum species of PACl1 could selectively bind to the HA site with strong binding, especially Al13 under the weak acidic condition. While for PACl2, complexation of small and median polymeric aluminum species, charge neutralization effect of Al13, and the effect of sweep coagulation of large polymeric aluminum species were involved. Moreover, diversity of hydrolyzed aluminum species in the coagulation process presented a significantly impact on flocs characteristics. This study provided a new insight into the relationship between HA and aluminum speciation and transformation for Al-based coagulants, which can be indicative to select suitable coagulants according to the water quality in the coagulation process.

Neutral and Multicharged Ions of Small Aluminum Oxides: Structures, Spectroscopy, and Energetics.

We use accurate ab initio methodologies at the Coupled Cluster level to compute the stable forms of AlxOyq+ (x = 1, 2; y = 1, 2; q = 0-3) species for which we derive an accurate set of geometrical and vibrational spectroscopic data. We also determine their adiabatic single, double, and triple ionization energies. These spectroscopic and thermodynamical data may help for identifying these species in laboratory, in astrophysical media, and in plasma and confirm previous observations of multi-charged AlxOy clusters by Atom Probe Tomography (ATP) coupled to mass spectrometry. They should help for identifying and understanding the complex chemical processes occurring during the Al2O3 growth in laboratory and in astrophysical media and those taking place at the degradation of Al-containing materials by high temperature corrosion/oxidation.

RANCANGAN PERCOBAAN INFRARED THERMOMETER: KALIBRASI DAN KEUNGGULAN PEMANFAATANNYA

His experiment aims to determine whether the reading of the infrared thermometer depends on the distance or angle of the incident ray, know the calibration and validation of the infrared thermometer and determine the temperature as a function of position and time for 1-D and 2-D objects and analyze the measurement results. The first experiment was carried out on objects with different areas, namely walls and small aluminum slabs with a size of 3.8cm x 3.8cm. The second experiment was also conducted on different objects, namely water with a temperature of 30oC and 60oC, which was measured at the same temperature using an infrared thermometer and an alcohol thermometer. The third experiment was carried out on 1D objects with 2 different types of materials and one type of 2D material. From the results of the experiment it can be concluded several things, for experiment one obtained differences in the reading of the thermometer at various angles and distances for object 2 (small plates), while for objects with large areas such as thermometer reading walls remain the same for different distances and angles. The thermal conductivity coefficient of aluminum is greater than iron.

Atomistic Structures, Stabilities, Electronic Properties, and Chemical Bonding of Boron–Aluminum Mixed Clusters B3Al0/−/+n (n = 2–6)

Neutral, anionic, and cationic B3Aln0/−/+ (n = 2–6) clusters were systematically explored using density functional theory and coupled cluster CCSD(T) methods to investigate the structural evolution of small mixed aluminum–boron clusters. The lowest energy structures of these clusters were obtained using an unbiased global minimum search, and their structural growth behaviors are discussed. The three boron atoms in B3Aln0/−/+ preferentially form a stable triangle, with additional Al atoms occupying the periphery of the boron triangle. For small clusters of n ≤ 3, the studied clusters show planar two–dimensional configurations. When n ≥ 4, the clusters prefer three–dimensional configurations. Average binding energies, fragmentation energies, second–order differences, HOMO–LUMO gaps, ionization potentials and electron affinities are discussed in detail. For cationic B3Aln+ (n = 2–6) clusters, the even n systems are more stable than the odd n systems, while the stabilities of neutral B3Aln and anionic B3Aln− clusters do not change significantly with growing n. The infrared spectrum and photoelectron spectroscopy of these clusters are simulated, which will be useful for future experimental research. We also compare the chemical bonding of neutral B3Aln (n = 2–6) clusters with their ionic clusters by AdNDP analysis.

Copper Oxide Passivation Effect on Electromigration Lifetime of Plasma Etched Copper Lines

Copper (Cu) is a widely used interconnection material in high density ICs, large area TFT LCDs etc. CMP is a production method used in etching Cu fine lines in ICs [1,2]. Although plasma etching is widely used in preparing small geometry aluminum and other metal lines [3], it cannot be used to etch Cu at room temperature due to the low volatility of copper halides [4]. A plasma-based high-rate, room-temperature Cu etch process was invented by Kuo’s group [5-7]. It includes the plasma/Cu reaction followed with a dilute HCl dipping step. This process has been successfully demonstrated on BiCMOS and TFT LCD products [8,9]. The electromigration (EM) method has been used in the evaluation the reliability of Cu lines [10-14]. Recently, the authors have reported that copper oxide (CuOx) is a potential useful passivation material for Cu line [15]. In this study, layer thickness effects of Cu and CuOx passivation films on the reliability are studied.The TiW/Cu stack was sputter deposited on a pre-cleaned Corning glass and etched into a 4-point line pattern. The Cu layer was converted into a CuClx layer under the condition of CF4/HCl 5/20 sccm, 70 mTorr, 600W, and room temperature for 2 minutes in a parallel-plate reactor (PlasmaTherm 700C) operated at the RIE mode. The CuClx layer was subsequently dissolved in a H2O:HCl (8:1 v/v) solution for 1 minute. Then, the TiW barrier film was etched in CF4 20 sccm at 60 mTorr and 600 W for 2 minutes in the same RIE reactor. After the photoresist pattern was wet stripped off, the sample was exposed to the O2 plasma at 200 mTorr, 100 W in the same plasma reactor but under the plasma etching mode. The CuOx passivation layer was formed on the exposed Cu surface. The EM lifetime of two types of samples, i.e., TiW/Cu and TiW/Cu/CuOx lines, were measured under the constant current density (J) stress condition.Figure 1 shows the line broken time as a function of the stress current density of TiW/Cu/CuOx lines of different Cu film thickness. The general trend is that the lifetime of the line decreases with the increase of the current density. This result is consistent with previous reports on the TiW or Mo passivated Cu lines [14]. The large stress current accelerated the voids formation and merging process, which shortened the line breakage time. Fig. 1 also shows the sample with the thinner Cu layer has a longer lifetime than with the thicker Cu layer. This can be explained by more resistant to thermal strain and the longer thermal fatigue failure time of the thin Cu film [16].Figure 2 shows the top view of a TiW/Cu/CuOx line broken region observed under the dark-field (DF) of an optical microscope. It clearly shows the distribution of a large number of voids along the current flow direction in this region while the adjacent unbroken region has much fewer voids.More detailed characterization of the EM stressed lines and the CuOx passivation layer thickness effect will be presented and discussed.Authors acknowledge the financial support of this work through NSF CMMI project 1633580. J. Proost, T. Hirato, T. Furuhara, K. Maex and J.-P. Celis, J. Appl. Phys., 87(6), 2792-2802 (2000).C. S. Hau-Riege, S. P. Hau-Riege and A. P. Marathe, J. Appl. Phys., 96(10), 5792-5796 (2004).D. A. Danner, M. Dalvie and D. W. Hess, J. Electrochem. Soc., 134(3), 669-673 (1987).H. Miyazaki, K. Takeda, N. Sakuma, S. Kondo, Y. Homma and K. Hinode., J. Vacuum Science and Technology B, 15(2), 237-240 (1997).Y. Kuo and S. Lee, Japan J. of Appl. Phys., 39(3A), L188 (2000).S. Lee and Y. Kuo, J. Electrochem. Soc., 148(9), G524-G529 (2001).Y. Kuo and S. Lee, Appl. Phys. Lett., 78(7), 1002-1004 (2001).Y. Kuo and S. Lee, Vacuum, 74(3-4), 473-477 (2004).J. Yang, Y. Ahn, J. Bang, W. Ryu, J. Kim, J. Kang, M. S. Yang, I. Kang, I. Cung, ECS Trans., 16(9), 13 (2008).C. S. Hau-Riege, Microelectronics Reliability, 44(2), 195-205 (2004).G. Liu and Y. Kuo, J. Electrochem. Soc., 156(7), H579-H584 (2009).C.-C. Lin and Y. Kuo, J. Appl. Phys., 111(6), 064909 (2012).M. Li and Y. Kuo, ECS Trans., 86(8), 41-47 (2018).J. Q. Su, M. Li, Y. Kuo and S. Hamaguchi, ECS Trans., 92(5), 39-46 (2019).J. Q. Su and Y. Kuo, ECS Trans., Submitted (2020).R. Mönig, Y.-B. Park and C. A. Volkert, AIP Conf. Proc., 817(1), 147-156 (2006). Figure 1

Aluminum Oxide Nanoparticle Films Deposited from a Nonthermal Plasma: Synthesis, Characterization, and Crystallization.

Aluminum oxide, both in amorphous and crystalline forms, is a widely used inorganic ceramic material because of its chemical and structural properties. In this work, we synthesized amorphous aluminum oxide nanoparticles using a capacitively coupled nonthermal plasma utilizing trimethylaluminum and oxygen as precursors and studied their crystallization and phase transformation behavior through postsynthetic annealing. The use of two reactor geometries resulted in amorphous aluminum oxide nanoparticles with similar compositions but different sizes. Size tuning of these nanoparticles was achieved by varying the reactor pressure to produce amorphous aluminum oxide nanoparticles ranging from 6 to 22 nm. During postsynthetic annealing, powder samples of amorphous nanoparticles began to crystallize at 800 °C, forming crystalline θ and γ phase alumina. Their phase transformation behavior was found to be size-dependent in that powders of small 6 nm amorphous particles transformed to form phase-pure α-Al2O3 at 1100 °C, while powders of large 11 nm particles remained in the θ and γ phases. This phenomenon is attributed to the fast rate of densification and neck formation in small amorphous aluminum oxide particles.

Deformation of small diameter aluminum alloy (AA6063T5) circular tubes subjected to lateral low-velocity impact

Abstract This paper presents an experimental and theoretical study on the deformation of small diameter aluminum alloy (AA6063T5) circular tubes under lateral impact loading. Seven specimens classified as three groups were investigated by the drop weight test. The patterns and extent of damage between specimens were compared and discussed. Moreover, the experimental results show that the performance of specimens subjected to the lateral impact is significantly affected by the diameter-thickness ratio and impact energy while the impact momentum has little effect. The springback of the global displacement is found to be negatively correlated with the ratio of the impact energy and the diameter-thickness ratio. Afterward, this study develops an analytic solution on the elastoplastic global displacement of AA6063T5 tubes based on vibration theory. Compared to the experimental results, the elastic solution predicted the global displacement of the aluminum alloy specimens reasonably.

Pulsed Laser Influence on Temperature Distribution during Dual Beam Laser Metal Deposition

Wire-based Laser Metal Deposition (LMD-w) is a suitable manufacturing technology for a wide range of applications such as repairing, coating, or additive manufacturing. Employing a pulsed wave (pw) laser additionally to the continuous wave (cw) process laser has several positive effects on the LMD process stability. The pw-plasma has an influence on the cw-absorption and thus the temperature distribution in the workpiece. In this article, several experiments are described aiming to characterize the heat input during dual beam LMD. In the first setup, small aluminum and steel disks are heated up either by only cw or by combined cw and pw radiation. The absorbed energy is then determined by dropping the samples into water at ambient temperature and measuring the water’s temperature rise. In a second experiment, the temperature distribution in the deposition zone under real process conditions is examined by two-color pyrometer measurements. According to the results, the pw plasma leads to an increase of the effective absorption coefficient by more than 20%. The aim of this work is to achieve a deeper understanding of the physical phenomena acting during dual beam LMD and to deploy them selectively for a better and more flexible process control.

Development of AlMg35-TiH2 composite foaming agent and fabrication of small pore size aluminium foams

Abstract In the melt foaming process of aluminium foams, small pore size aluminium foam is difficult to fabricate, this is mainly due to the early decomposition and poor dispersion of foaming agent (usually TiH2). In this study, these two problems are solved concurrently by introducing a TiH2-AlMg35 composite foaming agent in the melt foaming process. The composite foaming agent was fabricated by premixing the foaming agent (oxidizing treated TiH2) into a low melting point master alloy (AlMg35) melt. Microstructure and particulate distribution of the composite foaming agent were examined. Suitable dispersing parameters were obtained. Aluminium foams, with small pore size, better porous structure uniformity and good process controllability were fabricated using the TiH2-AlMg35 composite foaming agent. Average pore size reached as small as 0.6mm. This process has a simple procedure, low cost, and is suitable for commercial production.