Aluminum Alloy Tubes Research Articles

Relationship among joined tubular material properties, joining behavior and performance by elastomeric swaging

Joining by elastomeric swaging (ES) is a deformation-based way to manufacture tubular form-fit joints composed of aluminum alloy (AA) tubes and high-strength steel sleeve-fittings. To explore the relationship among the joined tubular material properties, joining behavior and performance of tubular form-fit joints fabricated by elastomeric swaging (ES), this paper took 6061-T4 and 5052-O AA tubes as material cases and carried out a comprehensive investigation by modeling and experiments. In terms of these two AA tubes, their microstructure was characterized by means of EBSD; their mechanical properties were characterized by tension tests based on digital image correlation and Visco-plasticity Self Consistent modeling. The characterization results demonstrate that the 6061-T4 tube has precipitation strengthening mechanism, texture unfavorable to shear, no Portevin–Le Chatelier (PLC) effect, larger strain hardening exponent and higher strength. In view of process, based on the material modeling for anisotropic AA tubes, hyperelastic polyurethane elastomer hose and 15-5PH sleeve, implicit axisymmetric numerical models of ES joining process with loading and unloading were established and validated. The simulation results show that there is a larger normal deformation in the 5052-O tube under the same extrusion depth and rate, and at the same bulging heights as 5052-O, the 6061-T4 tubular joints have larger residual contact shear stress at the undercuts. As for service performance, the ES joining tests and joining performance verification experiments were carried out. The experimental results show that the 6061-T4 tubular joining components have higher pressure resistance, larger pull-out force and better fatigue endurance. In conclusion, the joined tubes with texture unfavorable to shear, higher strength, larger strain hardening exponent and no PLC effect are beneficial to forming form-fit joints.

Characterization of high frequency welded aluminium microfin tube for heat exchangers

An aluminium alloy tube produced using linear high frequency welding of a strip consisting of a 3xxx-series alloy core with an embossed inner part and a thin 7xxx-series outer clad layer has been investigated in this work. Characterization techniques such as scanning electron microscopy, energy dispersive X-ray spectroscopy, electron backscatter diffraction, optical microscopy, and X-ray tomography have been utilized to understand the change in microstructure due to embossing and welding process. It is found that welding creates a high-quality joint without any observable flaws along the weld. The weld region contains a deformed microstructure as a result of compression applied during welding. The width of this plastically deformed region is 150–200 μm. On both sides adjacent to the deformed weld region there are approximately 250–300 μm-wide partially recrystallized heat-affected zones. The rest of the tube retains the deformed microstructure of the embossed strip. The microhardness of the welded tube follows the microstructural variations, with higher values in the deformed regions and lower values in the partially recrystallized heat-affected zones. The influence of the manufacturing process on the observed microstructural characteristics is discussed.

Experimental Investigation of Illumination Performance of Hollow Light Pipe for Energy Consumption Reduction in Buildings

This work investigates the light illumination intensity, light transmission performance, light distribution on the floor, and daylight factor of vertical light hollow tubes at various incident elevation angles of a light source. The light tubes were made from commercial aluminum alloy sheets and commercial zinc alloy sheets to investigate internal illuminance for buildings and reducing the demand of electrical energy from artificial lighting. The vertical light tubes with a constant length of 0.5 m and diameters of 0.20, 0.25, and 0.30 m were designed in a testing room model, with dimensions of 1 m × 1 m × 1 m. A 20-W light-emitting diode (LED) lamp was used as the light source for the lighting simulations, which was placed away from the top of the light tube. The incident elevation angle of the light source was changed between 0° and 80° with 5° increments. It was found that the elevation angle of the incidence light had an influence on the light intensity distribution on both ends of light tube. The average illuminance performance of both material types increased with an increase of the incidence angle from 0° to 80° and an increase of the tube diameter from 0.20 m to 0.30 m. The commercial aluminum alloy tube promotes greater light transmission and daylight factor when compared with the commercial zinc alloy tube in each condition. This illuminance measurement demonstrates that the light tube could be included in the lighting systems of some deeper or windowless areas of buildings to decrease the demand of energy consumption in the lighting of buildings.

Investigation of Friction-Stir Welding Parameters in the Fabrication of a 2-Layer Aluminum–Copper Pipe with Monolithic Interface

In this study, the friction-stir welding process was used to fabricate a 2-layer pipe consisting of AA5086 aluminum alloy and Cu12200 pipes. The welding was done with cylindrical and conical pin tool. The effect of rotational speed and linear velocity of the tool on the microstructure, macrostructure and mechanical properties of the joints was investigated. In this study, AA5086 aluminum alloy tube was placed upon the copper tube. Macro-studies have shown that at a rotational-travel speed ratio of 5–15 rev/mm using a conical pin tool and at a rotational-travel speed ratio of less than 10 rev/mm using a cylindrical pin tool, the tunnel defect was created in the weld cross section. The heat input is a more effective factor than the strain applied during the process, on the grain size of the stir zone. The cylindrical pin tool at rotational speed 600 rpm and travel speeds of 40 and 60 mm/min results in sound weld and a 2-layer Al/Cu pipe with monolithic interface. The effective bonding thickness and the distribution of copper particles and intermetallic compounds are important factors in achieving maximum joint strength.

Macro-meso Scale Coupling Modeling and Simulation of Surface Roughening in Aluminum Alloy Tube Bending

Macro-meso Scale Coupling Modeling and Simulation of Surface Roughening in Aluminum Alloy Tube Bending

Variation of the 90° Redundant-hole Diameter Effect on the Response and Failure of Round-hole 6061-T6 Aluminum Alloy Tubes under the Cyclic Bending

This paper presents an experiment and an analysis for examining the variation of the 90° redundant-hole diameter effect on the cyclic bending mechanical behavior and fracture failure of round-hole 6061-T6 aluminum alloy tubes. In this investigation, a round-hole 6061-T6 aluminum alloy tube with a 6 mm hole diameter was drilled to obtain a 90° redundant hole but with different hole diameter of 2, 4, 6, 8, or 10 mm. It can be observed that from the first bending cycle, the bending moment-curvature curve describes a stable loop. The diameter of the 90° redundant hole has little effect on the bending moment-curvature relationship. However, when the number of bending cycles increases, the ovalization-curvature curve shows an increasing, asymmetrical, ratcheting, and bow-like tendency. The diameter of 90° redundant-hole shows a significant influence on the ovalization-curvature relationship. In addition, five non-parallel straight lines corresponding to five different 90° redundant hole diameters were discovered for the controlled curvature-number of bending cycles necessary to cause failure relationship on the double logarithmic coordinates. Finally, a formula was presented to simulate the above relationship. It is found that the experimental and analytical data were in good agreement.

FORMATION OF ANODIC POROUS ALUMINA IN OXALIC ACID AND ELECTRODEPOSITION OF NI.

Nanoporous anodic aluminum oxide (AAO) tubular membranes were fabricated from aluminum alloy tubes in sulfuric and oxalic acid electrolytes using a two-step anodization process. The membranes were investigated for characteristics such as pore size, interpore distance and thickness by varying applied voltage and electrolyte concentration. Morphology of the membranes was examined using light optical and scanning electron microscopy and characterized using Image software. Results showed that membranes having narrow pore size and uniform pore distribution with parallel channel arrays were obtained. The pore sizes were ranging from 10 to 100 nm and the wall thicknesses 60 μm. The catalysts are obtained by impregnation of 3d metals into nanosized pores of aluminum oxide. The obtained catalysts based on nickel and porous Al2O3 are studied by scanning microscopy (SEM-EDX). The results of SEM-EDX analysis shows that a spongy structure with filament sizes of 100 nanometers containing particles of 3d metals formed on the surface of the aluminum oxide matrix.

Deformation Behavior Causing Excessive Thinning of Outer Diameter of Micro Metal Tubes in Hollow Sinking

The deformation behavior of microtubes during hollow sinking was investigated to clarify the mechanism of the excessive thinning of their outer diameters. Stainless-steel, copper, and aluminum alloy tubes were drawn without an inner tool to evaluate the effect of Lankford values on outer diameter reduction. Drawing stress and stress-strain curves were obtained to evaluate the yielding behavior during hollow sinking. The observed yielding behavior indicated that the final outer diameter of the drawn tube was always smaller than the die diameter due to the uniaxial tensile deformation starting from the die approach end even though the drawing stress was in the elastic range. The results of a loading-unloading tensile test demonstrated that the strain remained even after unloading. Therefore, the outer diameter is considered to become smaller than the die diameter during hollow sinking due to microscopic yielding at any Lankford value. Furthermore, the outer diameter becomes smaller than the die diameter as the Lankford value increases, as theorized. As the drawing stress decreases or the apparent elastic modulus of the stress-strain curve increases, the outer diameter seems to approach the die diameter during unloading, which is caused by the elastic recovery outside the microscopic yielding region.

Experimental studies on the impact characteristics of seamless fibre metal laminate (FML) tubes

The aim of this study was to investigate the energy absorption and impact characteristics a new tubular and seamless type of Fibre Metal Laminate (FML) fabricated from braided fibreglass sleeve and aluminium alloy tubes. Aluminium tubes was precisely machined to specific thickness then chemically treated to improve the adhesive bonding. Sleeve type braided fibreglass was selected as it comes in specific dimension and more importantly, it is seamless and produces an excellent composite tube. Tubes carefully assembled to form 2/1 and 3/2 layup configurations and highly adhesive resin was introduced as interlayer, which is composed of two layers of aluminium tubes and one layer of glass fibre braided sleeve in between for 2/1 layup. The new designed tubes were tested together with aluminium bare tubes with identical mass and inner dimension to 2/1 tube to evaluate the behaviour and impact characteristics under low velocity axial impact loading. This tube crushed progressively and unlikely to fail under catastrophic failure. The results also indicate that the mechanical performance of a new FML tube have a good potential to be applied as a new and efficient energy absorber.

Reaction Behavior, Microstructure, and Radiative Properties of In Situ ZrB2-SiC Ceramic Composites from a Si-Zr-B4C System

The present work focuses on the in situ self-propagating high-temperature synthesis (SHS) of ZrB2-SiC (ZS) ceramic composites in a Si-Zr-B4C system. The reaction process characteristics, microstructure and radiative properties of products were investigated. The thermal conductivity of ZS/acrylic composite coating filled with 40 wt.% ZS is 1.77 W/m K, which is ninefold enhancement in comparison with neat acrylic coating. In addition, in situ ZS/acrylic composite coatings showed an excellent increase in infrared emissivity up to 0.93 for 45 wt.% in situ ZS content, which was nine times more than bare aluminum alloy substrate. The produced coatings remarkably increased the heat dissipation performance of an aluminum alloy tube by 17.9%, implying a promising prospect for real passive heat dissipation applications.

Hot Gas Forming of Aluminum Alloy Tubes Using Flame Heating

Hot metal gas forming (HMGF) is a desirable way for the automotive industry to produce complex metallic parts with poor formability, such as aluminum alloys. A simple hot gas forming method was developed to form aluminum alloy tubes using flame heating. An aluminum alloy tube was heated by a flame torch while the tube was rotated and compressed using a lathe machine and simultaneously pressurized with a constant air pressure. The effects of the internal pressure and axial feeding on expansion and wall thickness distribution were examined. The results showed that the proposed gas forming method was effective for forming aluminum alloy tubes. It was also indicated that axial feeding is a vital parameter to prevent reductions in wall thickness by supplying the material flow during the forming process.

Effect of Variable Tube Wall Thicknesses of Al-Mg-Si Alloy Tube During Electromagnetic Compression using Four Turn Axi-Symmetric Coil

Electromagnetic compression (EMC) is a solid state, high velocity process of deformation of materials. In this process the enhancement of the formability is achieved due to high strain rate forming. In the present study Aluminum alloy AA6061 tube has been compressed using four turn axisymmetric coil. The effect of variable tube wall thicknesses i.e. 1.0, 1.7, and 2.4 mm during the compression of the Al-Mg-Si Aluminum alloy tube electromagnetically has been studied. A constant gap between coil inner diameter (ID) and workpiece outer diameter (OD) was maintained. It has been found that the tube deformation was maximum when the wall thickness was minimum. For compression, 8 kJ energy was used with double power bank. A three dimensional (3D) model of four turn compression coil has been proposed using LS-DYNA software. Comparison between the numerical simulation and experimental results showed a close agreement between both the results. Compression using EMF process can be used in modern industries like automotive, aerospace and nuclear power plants.

Experimental investigations on the implosion characteristics of thin cylindrical aluminium-alloy tubes

Experimental studies are conducted to investigate the implosion characteristics of thin cylindrical aluminium-alloy tubes. The effects of various parameters that generate different responses on the implosion behaviours are investigated. Aluminium-alloy tubes are fabricated from a 6061-T6 material and designed in the range of 2.5–6.7 length-to-diameter ratios; wall thickness-to-diameter ratios are varied from 55 to 69. The geometric imperfection parameters, defined as the initial ovality and thickness unevenness, are considered. Two different pressurising media, i.e., water only and the combination of water and nitrogen gas are employed. In addition small- and medium-sized of pressure chamber are utilised to clarify the pressure drop after the ultimate strength reached. Furthermore, non-linear finite element analyses, benchmarked for quantitative validation and comparison of the imploded tubes, are conducted. The numerical benchmark quantities are initial ovality, thickness unevenness, and air-backed fluid cavity parameters. The results of these experiments indicated that the effects of combined water and nitrogen can reproduce a constant pressure environment similar as actual undersea conditions, but the combined pressuring media can reduce the pressuring rate.

Experimental Study of Cyclic Bending Failure for Round-hole Tubes with a Redundant Round Hole in the Same Direction but Different Cross Sections

This paper presents the influence of a redundant round hole in the same direction but different cross sections on the response and failure of round-hole 6061-T6 aluminum alloy tubes subjected to cyclic bending. In this study, round-hole 6061-T6 aluminum alloy tubes with a constant hole diameter of 6 mm were drilled to obtain a redundant round hole in the same hole direction but different cross sections. The experimental results revealed that the moment–curvature relationship exhibited an almost steady loop from the beginning of the first cycle. The redundant round hole showed minimal influence on the moment–curvature relationship. However, the ovalization–curvature relationship demonstrated an asymmetrical, increasing, ratcheting and bow pattern along with the bending cycle, while the redundant round hole showed a significant influence on this relationship. In addition, six groups of round-hole 6061-T6 aluminum alloy tubes were tested, the controlled curvature-number of bending cycles required to ignite failure relationships on double logarithmic coordinates exhibited nonparallel straight lines. Finally, a theoretical model was proposed for simulating the controlled curvature–number of cycles to ignite failure. The simulation result was compared with experimental test data, which showed generally good agreement.

Stability research on spinning of ultra-thin-wall aluminum alloy tube

In this paper, the instability in spinning process of ultra-thin-wall tube is analyzed, and the influence law of different parameters of roller and main process parameters in spinning forming process. Firstly, the forward spinning finite element model of ultra-thin wall tube is established and its reliability is verified. It is concluded that the instability of ultra-thin-wall aluminum alloy tube during spinning is caused by its poor rigidity and material flow disorder. The effects of different parameters of roller (roller diameters, roller forming angles and roller corner radii) and the main process parameters (feed rates, friction coefficients and thinning rates) on the equivalent plastic strain and diameter expansion amount in spinning forming process were investigated. The results show that the influence of each parameter on the stability of ultra-thin-wall is quite different. The influence of roller corner radius is stronger than roller diameter and much stronger than roller forming angle. The influence that feed rate does the expansion amount to exist a minimum value. The friction coefficient and thinning rate have positive correlation with expansion amount. The optimum combination of process parameters was further determined, and the accuracy of the results was verified by experiments, which provided reference and guidance for actual production.

Numerical and experimental studies on thin-walled aluminum alloy tube hydroforming using differential lubrication method

In this paper, it was analyzed that the friction forces that affected the material flow were influenced by the friction coefficient and the load path of internal pressure and feeding in T-shaped tube hydroforming process. Therefore, a novel differential lubrication method was proposed to adjust the material flow through changing the friction coefficient in the asymmetric zone in the T-shaped tube besides the loading path design method. The differential lubrication zones in T-shaped tube were divided, and a method called intermediate semiring differential lubrication was designed. The effects of differential lubrication and traditional uniform lubrication methods on the wrinkle, height of branch tube and wall thickness distribution of the T-tube were investigated under the same loading path of internal pressure and axial feeding. Meanwhile, the differential lubrication methods were also simulated under the different loading paths of the internal pressure and axial feeding. The differential lubrication experiments of T-shaped tubes hydroforming were carried out with fluorosilicone grease and PEFT film as lubrication medium. The simulation and experimental results showed that the differential lubrication method more effectively avoided wrinkles in the back zone of the main tube, increased the height of branch tube and weakened the thickening than the traditional uniform lubrication method. And it was a promising way to improve the formability of T-shaped tube hydroforming and reduced the over-reliance on the loading path.

Electromagnetic impacting medium forming (EIMF) for aluminum alloy tube by using flat spiral coil

This paper proposes an innovative electromagnetic forming process for the manufacturing of aluminum alloy tubes, namely electromagnetic impacting medium forming (EIMF) process using flat spiral coil. The proposed EIMF process was implemented and characterized by numerical and experimental methods. Based on medium height and discharge energy, deformation region of tube was analytically determined and verified by finite element (FE) analysis. Effects of medium height and discharge energy for maximum diameter and strain rate of deformation tube were characterized numerically and experimentally. Flow defect of medium was observed at higher discharge energy. To estimate the effect of capacitance, four types of capacitance were designed and evaluated by numerical analysis. Through EIMF experiments, tubes with temperature from 25 °C to 200 °C were investigated and variations of maximum diameter (expansion ratio), thickness (thinning ratio) were obtained. Comparing with results under discharge energy, temperature has more obvious effects. Major and minor strains displayed higher level at 200 °C. Metallographic and morphologies were characterized by optical microscope (OM) and scanning electron microscopy (SEM). Results showed that refinement of average grain size and ductile fracture depends on the increase of discharge energy and temperature.

Crushing behavior and energy absorption property of carbon nanotube-reinforced aluminum composite foam-filled 6061 aluminum alloy tubes

Performance of a mechanical buffer can be significantly improved by strengthening the materials and optimizing its structure. Manufacturing of high-strength and light-weight foam-filled tubes (FFTs) has been proved to be an ingenious strategy. In this work, the in situ grown carbon nanotubes (CNTs) were used to reinforce aluminum (Al) foams. The FFTs were prepared by inserting CNT/Al composite foams (CFs) into 6061 Al alloy empty tubes (ETs). The crushing behavior and energy absorption property of the as-prepared CNT/Al FFTs (C-FFTs) were evaluated using uniaxial compressive tests. The results show that the adopted CFs can effectively interact with outside tubes in C-FFTs. The C-FFTs significantly improve the compressive performance and energy absorption property, but only slightly increase the structure weight compared to single ETs. The plateau stress and energy absorption capacity of C-FFTs are nearly 3.5 and 3.7 times higher than those of ETs, respectively. This phenomenon is ascribed to the stable support of CFs and the excellent load transfer ability of CNTs.

Experimental investigation on heat transfer characteristics of supercritical nitrogen in a heated vertical tube

The rapid variations of physical properties near the pseudocritical points and the unique heat transfer and resistance characteristics of supercritical fluids have gained a great deal of attentions in recent years. In this paper, the heat transfer characteristics of supercritical nitrogen in a heated vertical tube are investigated experimentally. The test section is an aluminum alloy tube of 6.6 m in length and 0.02 m in inner diameter with a wall thickness of 0.0085 m. The effects of different operating parameters, including pressure and mass flow rate of nitrogen, inlet temperature and mass flow rate of water, on the heat transfer characteristics are investigated. Meanwhile, the experimental data are compared with the predict values by different existing correlations, and all of them show large differences. Therefore, a new correlation has been developed to accurately predict the heat transfer coefficient based on the experimental data. The new correlation works well with 95% of the experimental data captured with a deviation of 20%. The experimental study and the new correlation may provide reference for the study of the heat transfer of supercritical fluid flow and design and operation of open rack vaporizer (ORV).

Experimental Analysis of Interference-Fit Joining of Aluminum Tubes by Electromagnetic Forming

This study investigates the main parameters that influence the strength of tubular component joints fabricated by electromagnetic compression, more specifically, interference fit by crimping tubes into mandrels. The mechanical parameters are the residual stress on the mandrel, the joining area, and the interfacial friction coefficient between the tube and mandrel. These parameters have a considerably complex relationship with electromagnetic compression process parameters, starting with the charging energy and distribution of magnetic pressure pulse that trigger the forming process, the initial gap between joining partners, the material components and geometry, and the shape and surface roughness of mandrel. This work investigates the interference-fit joining of AA6082-O aluminum alloy tubes with mandrels made of different materials (AISI 1045, AA6082-O, and AA6082-T6) and fabricated under different metallurgical conditions. The process is gradually analyzed by systematically considering the influence of other process parameters, such as the initial gap between joining partners, energy pulse, field shaper geometry and its resulting magnetic pressure, and mandrel material and surface roughness in order to fabricate joints with maximum strength. The derived results indicate, apart from the initial gap, the importance of the mandrel surface roughness and the field shaper geometry on the joint strength and its associated failure mechanism. These are presumed to be important contributions to the development and industrial implementation of EMF technology.