Aluminum Tubes Research Articles

Transverse indentation response and residual axial compressive characteristics of metal-composites hybrid tubes by deep learning-based acoustic emission and micro-CT

This work investigated transverse indentation response and residual axial compressive characteristics of Al-CFRP hybrid tubes with different configurations. The failure mechanism and damage evolution of the hybrid tubes under transverse indentation load were investigated by acoustic emission and micro-CT technologies. To gain an insight into the damage mechanism of CFRP composites, a structural health monitoring system based on image-based acoustic emission waveform and deep learning was developed. It showed that acoustic emission response of internal damage was corresponding to the damage visualization analyses of micro-CT. The proposed damage classification model provided a reliable path for extreme damage mode recognition and damage monitoring of composite structure. Under transverse indentation load, delamination and fiber breakage were the main failure modes of H-I hybrid tube (i.e. the CFRP tube internally filled with aluminum tube). For H-II hybrid tube (i.e. the aluminum tube internally filled with CFRP tube), the interfacial delamination of Al/CFRP tended to aggravate its failure behavior. The quasi-static axial compressive properties of intact and pre-indentation tubes were further compared to evaluate the effects of indentation damage on residual crashworthiness. The transverse indentation resulted in the change of the failure mode. Compared with H-I hybrid tube, H-II hybrid tube showed more significant property degradation.

Design and Simulation of a Square Loop Antenna for 920 MHz

This study describes design and simulation of a loop antenna. A square loop antenna is designed for 920 MHz. The loop antenna is then modelled and simulated using 4NEC2 electromagnetic (EM) modeling software. 4NEC2 is a completely free numerical electromagnetic modeling code. It is based on method of moments technique to solve electromagnetic boundary value problem. The 4NEC2 simulation of the loop antenna design predicted antenna resonant frequency to be 920 MHz, Return Loss bandwidth of 130 MHz and input impedance of 50.14 -j0.30 Ohm. The antenna radiation pattern is then simulated at 920 MHz. The Return Loss, VSWR, Input Impedance and Radiation Pattern of the antenna predicated by 4NEC2 simulation are studied for the possible development of copper or aluminium tube based loop antenna.

Enhanced refrigerant flow boiling heat transfer in microstructured finned surfaces

Flow boiling is used in air-conditioning and refrigeration, thermal management of electronics, distillation, chemical synthesis, desalination, power generation, and cryogenics. To enhance the flow boiling heat transfer, internally finned tubing has been widely used. In this work, we demonstrate a fabrication method to generate interal microstructures in 5.2 mm internal diameter finned aluminum tubing through crystallographic chemical etching to further increase heat transfer coefficients of low-GWP refrigerant R-515B. Enhancements in heat transfer coefficients are demonstrated across the range of vapor qualities with peak enhancements up to 172% observed at high vapor qualities with similar levels of enhancements demonstrated with R-134a. The effects of varying operating parameters such as heat flux, mass flux and saturation pressure, on performance improvement were also examined. Flow visualization studies performed through an adiabatic glass visualization section at the test-section exit allowed quantiification of film thickness and showcased lower conduction resistance for microstructured finned surfaces. The advantages of this structuring technique are further highlighted by the relatively minor increase in pressure drop (∼20%). We demostrate that etching of plain aluminum tubes exceeds the performance of finned tubing under high heat flux condtions, with enhancements being more pronounced at low mass fluxes, indicating potential replacement of current extrusion methods used for the manufacture of finned tubing. Surface characterization results after mechanical expansion of the etched finned tubing demonstrated the remenance of microstructures in fin valleys, thus proving potential compatibility with heat exchanger fabrication methods.

Multi-objective crashworthiness optimization of square aluminum tubes with functionally graded BCC lattice structure filler

The objective of this study is to find the optimum design configurations for the crashworthiness of functionally graded lattice structure filled aluminum tubes under multiple impact loading conditions. Base strut diameter, draft angle and aspect ratio are considered as filler material design parameters, and the optimal design configurations are sought for maximizing the specific energy absorption and minimizing the peak crush force. The finite element simulations are performed to establish the sample design space; linear and non-linear least square regression meta-models are developed to estimate the objective function values; the weighted superposition attraction-repulsion algorithm is employed to create design alternatives and seek their optimum combinations. The compromise programming technique is also adapted for combining multiple objectives and generating different optimum design options. The results revealed that the proper selection of design parameters can effectively enhance the crashworthiness performance of hybrid structures under multiple impact loading conditions. In particular, the results showed that the specific energy absorption value of square tubes can be improved up to 76% with the selection of appropriate lattice filler parameters. The present study provides a guideline for the optimum design of functionally graded lattice structure filled thin-walled structures under multiple impact loading conditions.

Experimental study on the impact resistance of hollow thin-walled aluminum alloy tubes and foam-filled aluminum tubes (6063-T5)

This paper presents a study on the axial impact resistance of hollow thin-walled aluminum alloy tubes and aluminum foam-filled thin-walled tubes. 15 hollow thin-walled aluminum alloy tubes and 15 thin-walled aluminum alloy tubes filled with aluminum foam were tested under drop hammer impacts. The process of the impact, the failure modes of the specimens, the time history curves of impact forces, and the vertical deflections were recorded in the test. The effects of impact velocity, aluminum alloy wall thickness, cross-sectional width, and aluminum foam on the performance of the hollow and aluminum foam-filled thin-walled aluminum alloy tubes were discussed. In addition, a finite element model was established to simulate the test considering the strain rate effect of aluminum alloy and aluminum foam. The results showed that both hollow and foam-filled thin-walled aluminum alloy tubes were damaged to different degrees. Under the same impact energy, the damage of the foam-filled thin-walled aluminum alloy tube was less severe than that of the hollow thin-walled aluminum alloy tube; under the axial impact load of the drop hammer, the most effective way to improve the impact resistance of the hollow and foam-filled thin-walled aluminum alloy tubes was to increase the wall thickness of the outer thin-walled aluminum alloy tube, while the effect of increasing the cross-sectional size of the outer thin-walled aluminum alloy tube on the impact resistance of the specimen is less significant. The peak impact force, vertical deflection and the duration of impact forces are most sensitive to the impact velocity.

Experimental Study on Strength Deformation Behavior of Large Diameter Thin-Walled Aluminium Alloy Tubes Subjected to CNC Bending

The strength deformation behavior of thin walled aluminium alloy 6063 tubes under flexure has been presented. The effects of deformation, thinning, thickening of the tube wall surfaces, ovalness of the tube and springback angleat critical cross sections of the aluminium tubes are studiedunder different computer numerical control (CNC) bending conditions. Aluminium alloy tubes of 25mm outer diameter, 390 mm length and varying thickness of 1, 1.5 and 3mm have been used for testing. It is observed that, thinning and thickening of inner and outer bend of tube gradually rises with increase in the bend angle and meantime surface flattening and non-circularity of tube in terms diameters also upsurges for the increase in bend angle.Furthermore, experimental outcome of deformed tube is compared and characteristic result for effect of experimental parameters is found to be in good agreement with literature values.

Performance analysis of a novel model of photovoltaic PV-TEGs system enhanced with flat plate mirror reflectors

Recently, the combination of photovoltaic (PV) modules and thermoelectric generators (TEGs) have shown optimal models of energy harvesting from solar photovoltaic/thermal systems. In this regard, the design of solar collectors with simpler models and compatible with TEGs attract attention. The following article is a report on the simulation of a simple new model of photovoltaic PV-TEGs system enhanced with flat plate mirror reflectors. The energy output of the system is hot water flowing in aluminum tubes with a rectangular cross-section connected to the cold surfaces of the series TEGs. Arranged experimental results were used for the power and efficiency relationships of the series of TEGs in the simulation. The results showed that the difference in electrical energy produced by PV module and TEGs due to the presence and absence of reflectors are equal to 1095.448 (kJ) and 80.874 (kJ), respectively. Also, the daily thermal efficiency of the system was about 42%.

Characterization of electroless nickel-phosphorus plating for ultracold-neutron storage

Electroless nickel plating is an established industrial process that provides a robust and relatively low-cost coating suitable for transporting and storing ultracold neutrons (UCN). Using roughness measurements and UCN-storage experiments we characterized UCN guides made from polished aluminum or stainless-steel tubes plated by several vendors.All electroless nickel platings were similarly suited for UCN storage with an average loss probability per wall bounce of 2.8 ⋅ 10-4 to 4.1 ⋅ 10-4 for energies between 90neV and 190neV, or a ratio of imaginary to real Fermi potential η of 1.7 ⋅ 10-4 to 3.3 ⋅ 10-4. Measurements at different elevations indicate that the energy dependence of UCN losses is well described by the imaginary Fermi potential. Some special considerations are required to avoid an increase in surface roughness during the plating process and hence a reduction in UCN transmission. Increased roughness had only a minor impact on storage properties.Based on these findings we chose a vendor to plate the UCN-production vessel that will contain the superfluid-helium converter for the new TRIUMF UltraCold Advanced Neutron (TUCAN) source, achieving acceptable UCN-storage properties with η=3.5(5)⋅10-4.

Sheet Pile Tuned Mass Damper for Construction Noise Control

Sheet piles are often used for underground retaining structures. For dense geology, vibratory driven method is more cost-effective than press-in driven method, but noisier. Conventional mitigations such as noise barrier or enclosure are not applicable due to the large size of pile wall (generally >12m high and >10m width). Acoustic camera images revealed that noise radiation was dominant at 630Hz to 2000Hz and mainly came from the sheet-pile wall rather than the vibratory exciter. Vibration response measurement showed the sheet piles had two major resonance modes at 1000 and 2000Hz. An innovative noise mitigation method was developed with 14 nos. of tuned mass dampers (TMD) distributed along a 5m long aluminum tube for vibration energy dissipation at the pile wall. Specific magnetic mounts were developed for quick and easy attachment of the TMDs at the construction site. In the site test, total 6 aluminum tubes (i.e., 84 TMDs) were mounted to the 1st, 2nd and 3rd piles adjacent to the driven pile on both sides. Vibration reduction was measured ~9 to 14dB at the pile wall. Noise reduction was measured 7 to 9dB(A) at 2 noise monitoring locations (~7m and ~22m from the pile wall).

Punchless Piecing Process of Aluminum Tube Wall by Impulsive Water Pressure

Punchless Piecing Process of Aluminum Tube Wall by Impulsive Water Pressure

Estimation of the local instantaneous heat flux inside a pulsating heat pipe for space applications

Pulsating Heat Pipes (PHP) are promising and effective passive two-phase heat transfer devices in terms of high heat transfer capability, efficient thermal control, adaptability and low cost and therefore they have been extensively studied in the last years. Many authors have estimated the heat fluxes at the evaporator and at the condenser area only in terms of the average values based on first principle considerations. In the present study the application of an inverse analysis technique to experimental infrared temperature data is proposed to investigate the local convective heat flux for forced convection flow inside these devices along the adiabatic zone. A PHP specifically designed to be hosted on board the heat transfer host of the International Space Station was tested in microgravity during the 67th Parabolic Flight Campaign organized by the European Space Agency. The device consists of an aluminium tube closed in a loop with 14 turns in the evaporator section, 3 mm inner diameter, half filled with FC-72 fluid. The external temperatures of the device are measured in the adiabatic zone with a high-speed infrared camera (50 Hz, 1280x1024 pixels). The images are thereafter post-processed and adopted as input data for the solution of the inverse heat conduction problem in the pipe wall (Tikhonov regularisation method) to extrapolate time-varying local heat fluxes on the tube internal surface in contact with the fluid.

Experimental investigation on the heat transfer performance of falling film with deionized water on horizontal tubes

Taking deionized water as working fluid, an experimental study was conducted to investigate the heat transfer characteristics of falling film evaporation outside horizontal aluminum tube with inner diameters of 10 mm and 14 mm. The effect of spray density, heat transfer temperature, evaporation temperature, tube diameter, outlet vapor quality and degree of undercooling on overall heat transfer coefficient outside the tube was analyzed. The results show that the overall heat transfer coefficient increases with increasing evaporation temperature and tube diameter while decreases with increasing heat transfer temperature difference and outlet vapor quality. On other hand, the overall heat transfer coefficient increases with increasing spray density firstly, then decreases slightly. The effect of outlet vapor quality can be neglect.

Fluid elastic instability and vortex shedding in finned tube arrays: the effects of tube material and fin density

PurposeThe purpose of this paper is to present investigations on the significant influence of the tube material and fin density on fluid elastic instability and vortex shedding in a parallel triangular finned tube array subjected to water cross flow.Design/methodology/approachThe experiment was conducted on finned tube arrays with a fin height of 6 mm and fin density of 3 fins per inch (fpi) and 9 fpi. A dedicated setup has been developed to examine fluid elastic instability and vortex shedding. Nine parallel triangular tube arrays with a pitch to tube diameter ratio of 1.78 were considered. The plain tube arrays, coarse finned tube arrays and fine finned tube arrays each of steel, copper and aluminium materials were tested. Plain tube arrays were tested to compare the results of the finned tube arrays having an effective tube diameter same as that of the plain tube.FindingsA significant effect of fin density and tube material with a variable mass damping parameter was observed on the instability threshold. In the parallel triangular finned tube array subjected to water cross flow, a delay in the instability threshold was observed with an increase in fin density. For steel and aluminium tube arrays, the natural frequency is 9.77 Hz and 10.38 Hz, which is close to each other, whereas natural frequency of the copper tubes is 7.40 Hz. The Connors’ stability constant K for steel and aluminium tube arrays is 4.78 and 4.87, respectively, whereas it is 5.76 for copper tube arrays, which increases considerably compared to aluminum and steel tube arrays. The existence of vortex shedding is confirmed by comparing experimental results with Owen’s hypothesis and the Strouhal number and Reynolds number relationship.Originality/valueThis paper’s results contribute to understand the effect of tube materials and fin density on fluid elastic instability threshold of finned tube arrays subjected to water cross flow.

A newly designed decoupling method for micro-Newton thrust measurement.

A decoupling method is proposed for micro-Newton thrust measurement with a torsion pendulum. The basic approach is to reduce the influences introduced by the propellant tube and wires of the thruster. A hollow aluminum tube is used to hang the torsion pendulum and is also chosen as the transport pipe for the propellant of the thruster. The electric control box of the thruster is mounted on the pendulum body, which is powered by an externally installed power supply through a liquid metal conductive unit. The control of the electric control box is performed through wireless transmission. With this design, the influences of the propellant tube and connection wires between the torsion pendulum and the outside device are reduced and the stability of the torsion spring constant of the system can be improved. The use of the liquid metal conductive unit reduces the coupling between the wires and the measurement system. The feasibility of the wireless transmission is analyzed. The error sources during the thrust measurement are analyzed, and the expected three σ uncertainty of the thrust is 0.032+(0.10%*F)2μN for the measurement of the cold gas thruster. The scheme provides a thrust measurement with higher precision and stability.

Research on Surface Defect Detection Method of Aluminum Tube Based on Ensemble Adaptive Undersampling

Research on Surface Defect Detection Method of Aluminum Tube Based on Ensemble Adaptive Undersampling

On the Effects of Driven Element L/D Ratio and Length in VHF-SHF Yagi-Uda Arrays

While the Yagi-Uda array has been studied for decades, one issue appears to have received less attention than perhaps it should, namely, the effects on performance of the array’s driven element length and its length-to-diameter ratio. This paper looks at that question. It shows that decreasing the L/D ratio increases impedance bandwidth, but it may shift the IBW band sufficiently far from the design frequency that other parameters such as gain and front-to-back ratio probably are adversely affected. It also shows that array performance is not relatively independent of element diameters. This paper also investigates the effect of lengthening the driven element, which can substantially improve IBW. Several iterations of a 3-element prototype and improved arrays are modeled with the Method of Moments and discussed in detail. A five step design procedure is recommended and applied to a Genetic Algorithm-optimized 3-element Yagi at 146 MHz. This array exhibits excellent performance in terms of gain, front-to-back ratio, and especially impedance bandwidth (nearly 14% for voltage standing wave ratio ≤ 2:1 with two frequencies at which 50 ? is almost perfectly matched). While the analysis and recommended design steps are applied to cylindrical array elements, which commonly are aluminum tubing for stand-alone VHF-SHF Yagis, they can be applied to other element geometries as well using equivalent cylindrical radii, for example, Printed Circuit Board traces for planar arrays. One consequence of lengthening the driven element while reducing its L/D ratio is that some reactance is introduced at the array feedpoint which must be tuned out, and two approaches for doing so are suggested.

Differential flow velocities control method for push-bending of the thin-walled tube with a 0.9D bending radius by differential lubrication

The smaller the relative bending radius of the bent tube, the more difficult the tube blank is to be bent. In this paper, the push-bending process for the aluminum tube with a relative bending radius of 0.9D was analyzed through simulation. There was tangential tensile stress concentration occurring at the front endpoint of tube intrados, which increased the risk of cracking. That is because the bending tube’s extrados moves less angular distance than its intrados by the uniform lubrication method, causing excessive deformation of the cross-section. Therefore, a differential lubrication method using the lubricant with a larger friction coefficient at intrados and the lubricant with a smaller friction coefficient at extrados was proposed to increase the angular velocity of the tube’s extrados. It was found that the differential lubrication method helped avoid excessive thinning at the front endpoint of tube intrados through simulations. Furthermore, push-bending experiments of 5A02 aluminum alloy with a relative bending radius of 0.9D were carried out to investigate this effect. The experimental results showed that the differential lubrication method effectively avoided cracking, which agreed with the simulation results.

On crushing behavior of square aluminum/CFRP hybrid structures subjected to quasi-static loading

Metal/composite hybrid thin-walled structures exhibit tremendous merits on the balance design among material costs, weight reduction and mechanical performances. In spite of these advantages, their underlying energy dissipating mechanisms and the influence law of key factors (such as mechanical properties, hybrid ratio, loading angle, etc.) on crushing behavior are still not well illustrated. This study aims to comprehensively explore the crushing deformation characteristics and underlying energy dissipating mechanisms of various square aluminum/CFRP hybrid structures (i.e., aluminum tube internally strengthened with CFRP namely CFRP/AL; aluminum tube externally strengthened with CFRP namely AL/CFRP tubes). Specifically, several axial quasi-static compression tests are performed to compare crushing behavior and performances of between hybrid tubes together with the corresponding net aluminum and CFRP tubes. Experimental results indicate that the total energy absorption of the CFRP/AL hybrid tubes is considerably higher than that of the summation of corresponding individual tubes. Subsequently, finite element models are developed for CFRP/AL hybrid columns to explore the underlying energy-absorbing mechanisms (the contribution of each constituent part on total energy absorption) and the influence law of key factors (mechanical properties, hybrid ratio, loading angle), which cannot be observed from experimental results. Numerical results indicate that the main reasons for the improvement in total energy absorption of CFRP/AL hybrid tubes are the altered deformation pattern of the outer aluminum tube and the significantly increased friction energy. Further, their outer aluminum tube seems to be more likely to generate plastic folding deformation rather than splaying progressive failure mode with increasing initial yield stress. The hybrid ratio and CFRP layer thickness jointly determine the deformation pattern of the CFRP/AL hybrid columns. Finally, it is also found that the load carrying capacity and energy-absorbing characteristics of CFRP/AL hybrid columns gradually reduce with increasing loading angle. The present study is expected to illustrate the potential of such hybrid structure as a crashworthy device and offer some design guidance for application and dissemination.

Axial Compression Study of Crash Boxes with Various Honeycomb Structures

In recent times, automotive manufacturing companies are focusing on developing components that is capable of increasing safety features associated with lightweight materials such as using aluminium. One such innovation is providing the vehicle with crash box, which is generally located at the front bumper. The function of the crash box is to safeguard the passenger by absorbing the kinetic energy of collision and self-deformation. In this paper, the authors presented a study of the compressive test applied on crash boxes with different types of honeycomb sandwich circular columns using 3D virtual modelling and finite element (FE) simulation with the help of Solidworks and Ansys Workbench respectively. This sandwich structure comprises two circular aluminium tubes filled with core shaped as a large-cell honeycomb lattice. Here, the crash boxes with three different honeycomb sandwich circular columns i.e., hexagonal, triangular, and semi-circular arrangement, were investigated and the energy absorption capabilities of these columns were studied. FE simulations were used to evaluate maximum stress that a material can sustain over a period under a load, material deformation, geometric changes, and load-displacement results using a constant material property of that of aluminium alloy, and the results of the three different arrangements were compared and it is known that the crash box with semi-circular arrangement has high energy absorbing capacity.

Compression performances of composite aluminum foam tubes

Composite aluminum foam tubes (CAFTs) with different porosities and diameter ratios were fabricated by a developed melt foaming method. Metallurgical bonding between aluminum foam and aluminum tubes was realized. 3D models based on real specimens were established by X-ray tomography. Moreover, axial mechanical behavior and failure mechanism of CAFTs were investigated by quasi-static compression tests coupled with finite element simulation. Meanwhile, the effect of porosity and diameter ratio on its energy absorption capacity was analyzed. The results showed that the deformation process of CAFTs is more stable and controllable compared with thin-walled tubes. When diameter ratio increased from 0.22 to 0.44 and 0.67, specific energy absorption increased by 17% and 26% respectively. Moreover, compression performances of CAFTs can be controlled by foam core porosity and diameter ratio. Finite element simulation results showed that deformation of CAFTs started from aluminum foam core and interface bonding played an important role in coordinating with the deformation. High consistency between experimental results and finite element simulation results was demonstrated and the reasons were discussed.