Aluminum Shell Research Articles

Numerical Model, Parametric Analysis, and Optimization of FCC's 16 T Main Dipole Baseline Design

CERN is currently investigating the feasibility of a future collider - the Future Circular Collider (FCC) - as a potential successor of the Large Hadron Collider (LHC), providing scientists with a powerful discovery tool in the field of high energy physics. INFN developed the main 16 T Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn dipole of the FCC based on the cos-theta coil design. The baseline design of the superconducting magnet adopts the bladder-and-key concept and includes 4-layered asymmetric coils, an aluminum shell and a welded stainless-steel skin. The scope of this collaborative work between INFN, CERN, UPATRAS and FEAC, is to validate and further study the baseline design. This paper describes the design concept and the fully parametric multi-physics finite and boundary element (FEM and BEM) model. The baseline assembly parameters are presented while the study of geometrical, material and assembly parameters, unveils the optimized structure.

Preliminary Strain Measurement in High Field Superconducting Magnets With Fiber Bragg Grating

High field superconducting magnets are subjected to a large Lorenz force during operation. The main superconductors for high field applications like Nb₃Sn are strain sensitive, therefore it is essential to measure the strain in the superconducting (SC) coils during the testing process. Compared with the traditional way by using the Resistance Strain Sensor (RSS), the fiber optic sensor based on the Fiber Bragg grating (FBG) method has significant advantages in high field applications. The FBG is an anti-electromagnetic interference device, which makes it possible to measure the local strain inside the superconducting coils. Meanwhile, it is sensitive only to the strain at a constant low temperature (4.2 K). In this study, several FBGs and RSSs were impregnated in SC coils of a 12 Tesla dipole magnet, and FBGs were attached to the outer surfaces of the aluminum shell and rods. The test was performed in the whole process from room temperature assembly of the magnet to the excitation at 4.2 K. The experimental results show that FBGs can continually monitor the strain of the magnet from a macro perspective, as well as reflect the internal strain state of the SC coils during the whole process. Compared with RSSs, FBGs have a better performance in strain measurement during the excitation due to the anti-electromagnetic interference. Strain measurement inside the magnet can offer more useful information about the strain distribution of the magnet and the origin of the quench, which may help developers improve the design and fabrication of SC magnets.

Assembly and Mechanical Analysis of the Canted-Cosine-Theta Subscale Magnets

A two-layer subscale canted-cosine-theta 4.5 T has been built and successfully tested. The design of the magnet is based on Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn cable wound into aluminum bronze mandrels, and an external aluminum shell. The magnet was conceived as an agile platform for the development of canted-cosine-theta magnets and general magnet technology. The main fabrication, assembly and analysis processes developed for this magnet are discussed in detail. The training behavior and mechanical response of magnet’s structure in relation to previous canted-cosine-theta magnets are also discussed.

Buckling behaviour of FRP strengthened cylindrical metallic shells with cut-outs

This paper presents a detailed buckling study on FRP strengthening of metallic cylindrical shells with different geometric imperfections and centrally located unstiffened and stiffened cut-outs. Initially, bare and FRP strengthened aluminium cylindrical shells have been manufactured. Geometric imperfections have been measured and implemented in the numerical model. Interfacial bond quality has been assessed by two different non-destructive techniques. The buckling response of bare and FRP strengthened shells have been numerically simulated and validated with respective experiments. Subsequently, the difference in buckling response between FRP strengthened and bare aluminium shells with variations in cut-out’s size, orientation, shape, and corner radius has been analysed for unstiffened cut-outs. The effect of increase in stiffener’s thickness and overlap width for photo-frame type stiffening of rectangular cut-outs with and without closure has been investigated. The study has revealed interesting observations. (1) Effect of cut-out size on buckling capacity of the shell is a function of its imperfection magnitude. For shells with large initial imperfections, introducing a cut-out as well as with increase in its size, relatively smaller drop in buckling capacity is found; while shells with small initial imperfections resulted in a steep and large drop in buckling load even with a small cut-out size. (2) FRP strengthening is more effective for shells with cut-outs compared to shells without cut-outs, as it increases the flexural stiffness of shell against asymmetric buckles’ initiation and resists outward lip opening along longitudinal edge of cut-out. (3) For shells with large initial imperfections, elliptical cut-outs offer higher buckling resistance than rectangular cut-outs with varying corner radius but with FRP wrapping, rectangular cut-outs with rounded edges exhibit the best buckling performance. (4) In the case of shells with stiffened cut-out, both with or without closure, FRP strengthening is effective only for shells with smaller initial imperfections. Further findings and observations are discussed and concluded.

Semi-analytical and experimental studies on travelling wave vibrations of a moderately thick cylindrical shell subject to a spinning motion

Spinning cylindrical shells are the indispensable basic components of engineering structures and exhibit complicated dynamic responses, the experimental studies on travelling wave vibrations are rare. This work numerically and experimentally investigates the travelling wave vibrations of a spinning cylindrical shell, i.e. a cylindrical aluminium shell with the integrated flanges. A new third-order shear deformation theory (TSDT) is adopted for the moderately thick cylindrical shell. Chebyshev polynomials are utilized to accurately simulate the circumferential-wave-dependent mode functions and the classical boundary conditions of the shell. The natural frequencies of the travelling waves of the spinning cylindrical shell are derived via Ritz method. The bifurcation of the natural frequencies of the spinning cylindrical shell is experimentally observed and discussed. Experimental results validate the mode shapes and the natural frequencies of the travelling waves, where the movable simply-supported ends and the sliding ends are chosen to approximate the boundary condition of the integrated flanges. In addition, the numerical comparisons among the TSDT, the first-order shear deformation theory and Donnell’s shell theory against the natural frequencies are presented.

ICROSTRUCTURE EVOLUTION OF STEEL-ALUMINUM WIRE DURING DEFORMATION BY "EQUAL-CHANNEL ANGULAR PRESSING-DRAWING"METHOD

During experimental studies of the equal-channel angular pressing-drawing effect on the microstructure evolution and mechanical properties change, the principal possibility and effectiveness of using the proposed continuous method for forming an ultrafine-grained structure and increasing the strength properties of steel-aluminum wire was proved. The deformation was carried out at ambient temperature in three passes. It is shown that both layers of bimetallic wire are processed unevenly. An aluminum shell with an initial grain size of 22 microns was processed up to 2 microns. The steel core has a different grain size in the transverse and longitudinal sections. With an initial grain size of 18 microns, after deformation the grain size is about 10 microns in the longitudinal section and 8 microns in the transverse section.

Calculation of stresses initiated by an electric explosion of conductors in a composite thick-walled cylinder

The paper presents a dynamic loading analysis of a material carried out by the exploding wire method (EWM). A composite cylinder is chosen as an experimental sample. It is a thick-walled cylinder made of polymethyl methacrylate with an axial bore formed therein, pressed into an aluminium shell. The sample was loaded by applying an electric voltage to a conductor in the form of a copper wire placed inside the axial bore of the sample. An equation of state for an electric explosion of a conductor obtained. Dependence between the pressure in the air channel and the expansion coefficient of the EWM products demonstrated with comparison charts of the experimental and theoretical values. A theoretical model that describes the amplitude characteristic of the radial stresses arising during the loading is constructed, taking into account the boundary and initial conditions. The substantiation of the model accuracy is given by comparing the obtained results with experimental data. The estimation of the circumferential stress at which the aluminium shell breaks directly performed.

Rational Design and Porosity of Porous Alumina Ceramic Membrane for Air Bearing

Air bearing has been widely applied in ultra-precision machine tools, aerospace and other fields. The restrictor of the porous material is the key component in air bearings, but its performance is limited by the machining accuracy. A combination of optimization design and material modification of the porous alumina ceramic membrane is proposed to improve performance within an air bearing. Porous alumina ceramics were prepared by adding a pore-forming agent and performing solid-phase sintering at 1600 °C for 3 h, using 95-Al2O3 as raw material and polystyrene microspheres with different particle sizes as the pore-forming agent. With 20 wt.% of PS50, the optimum porous alumina ceramic membranes achieved a density of 3.2 g/cm3, a porosity of 11.8% and a bending strength of 150.4 MPa. Then, the sintered samples were processed into restrictors with a diameter of 40 mm and a thickness of 5 mm. After the restrictors were bonded to aluminum shells for the air bearing, both experimental and simulation work was carried out to verify the designed air bearing. Simulation results showed that the load capacity increased from 94 N to 523 N when the porosity increased from 5% to 25% at a fixed gas supply pressure of 0.5 MPa and a fixed gas film thickness of 25 μm. When the gas film thickness and porosity were fixed at 100 μm and 11.8%, respectively, the load capacity increased from 8.6 N to 40.8 N with the gas supply pressure having been increased from 0.1 MPa to 0.5 MPa. Both experimental and simulation results successfully demonstrated the stability and effectiveness of the proposed method. The porosity is an important factor for improving the performance of an air bearing, and it can be optimized to enhance the bearing’s stability and load capacity.

Investigation of the bending and crushing for the light-weight structures used in vehicle's radiator

Sandwich panels are widely used in various industries, including the aerospace industry, where they have long been regarded because of their light-weight and high energy absorption capacity. This research introduces a novel type of sandwich panel whose raw material is widely used in the automotive industry. The materials used for manufacturing the sandwich panels addressed in this research are currently used in the cooling radiator structure for the engine of conventional vehicles. Such a radiator is nothing but a lattice of a set of B-shaped tubes and cooling fins. In this research, the crashworthiness properties of such a lattice are extracted along with various directions (samples A, B, and C). Moreover, the applicability of the considered lattices as the core of sandwich panels was studied. This research showed that the considered structures tend to exhibit maximum strength when the loading plane is parallel to the cooling fins. It was further figured out that the addition of aluminum shells to specimens A, B, and C can increase their energy absorption capacity by 85, 268, and 13%, respectively.

Modelling of strains experienced by aluminium shells during machining

The study analyzes whether it is feasible to use high-strength aluminum alloys for making high-pressure cylinders. It is shown that replacing highstrength complex alloyed steel with the V95-like aluminum alloys is feasible. Aluminum alloys were not investigated for stresses and displacements occurred when workpieces are fixed in three-law grippers. The study is relevant because all the physical and mechanical properties of aluminum alloys (yield strength, ultimate strength) are about a third of the respective steel properties. Using the available references, we estimated the cutting force components and the clamping force at each jaw required to hold the workpiece in the gripper. Wide and long jaws are usually used to hold thin-wall shell workpieces in three-jaw lathe grippers. The total workpiece circumference coverage by the jaws is close to a full circle. The estimated force was applied to each jaw. A 3D model was created with SolidWorks and simulated. The simulation showed that the higher stress occurs mostly in the tooling parts amounting to 1.269...1.384 MPa. The stress in the gripper body segments contacting the jaws is 0.69...0.923 MPa. The most of the body is under a low stress: 0.015...0.023 MPa. The max stress in the workpiece is found at the lower edges of its bottom. The stress at the jaw-to-segment interface reaches 1.24 MPa. At these points, the wide jaws compress the workpiece; the segment at the center of the wide jaws is stiffer since there is a jaw and a stiffener behind its wall. There are three equally distributed stress points. Still, the stress in the rest of the segment is 0.015...0.023 MPa. The deformed workpiece has a faceted shape. The out-of-roundness is 0.0014 to 0.00165 mm. It is well below the out-of-roundness tolerance.

Optimum cooling surface for prismatic lithium battery with metal shell based on anisotropic thermal conductivity and dimensions

Battery thermal management system (BTMS) is important for the battery pack in electric vehicles. Existing literature focuses on the structure of BTMS but not on the selection of the optimal cooling surface of the battery. To the authors’ knowledge, this study first investigates the optimum cooling surface for prismatic lithium battery based on anisotropic thermal conductivity, dimensions, and metal shell. The specific heat, thermal conductivity, and heat generation are measured experimentally to establish a three-dimensional (3D) shell cell separation numerical model. Results show that aluminum shell plays the role of fin and enhances the cooling effect. Cooling on surface B has better effect when the aluminum shell thickness is less than 0.3 mm; otherwise, cooling on surface A is better. The cooling effect can be improved by increasing the thickness and area of aluminum shell. Battery temperature rise reduces by 67.5% when the thickness changes from 0 mm to 1 mm. A negative linear correlation exists between the temperature rise of the battery and the cooling area. Double surface cooling reduces the temperature rise by 24.1% compared with single surface cooling. The investigation on optimal cooling surface can guide the selection of cooling form of BTMS.

Research and Application of Electromagnetic Wave Signal Acquisition Device for Power System Circuit Breaker

Power circuit breaker is an important tool to satisfy the controllability and safety of power system. Therefore, to ensure the stable operation of the circuit breaker is to ensure the normal supply of electric energy. In order to better capture the electromagnetic wave signal radiated by the circuit breaker and better judge the state of the electromagnetic wave radiated by the arc of the circuit breaker, a new type of vibration trigger device specially used for collecting the electromagnetic wave signal radiated by the circuit breaker and its use method are proposed in this paper. This method can collect the electromagnetic wave signal of circuit breaker through the optimized design of vibration trigger device. The device uses all metal integrated cast aluminum shell and independent power supply. This device can effectively resist electromagnetic interference, and is convenient for the acquisition of electromagnetic wave signal. The device developed in this paper and its application method belong to the field of off-line detection of electrical equipment, and are especially suitable for vibration triggering of the device when collecting the radiated electromagnetic wave signal during the action of circuit breaker.

Effect of Rotary Forging on Microstructure Evolution and Mechanical Properties of Aluminum Alloy/Copper Bimetallic Material

The influence of a degree of strain by rotary forging, as well as post-deformation annealing on the structure and mechanical properties of a clad aluminum alloy/copper bimetallic material was studied. Rotary forging of the initial bimetallic billet was carried out step by step from a diameter of 20.1 mm to a diameter of 2.4 mm. Rotary forging of the aluminum alloy/copper bimetallic material to a diameter of 5.3 mm leads to the formation of a mixed fine-grained and nanocrystalline oriented structure in an aluminum shell and to a decrease in the average grain size by 4.5 times and to an increase in the density of crystalline defects in a copper core. A reduction in the aluminum alloy/copper bimetallic material diameter to 2.4 mm (with intermediate annealing) leads to the formation of a fine-grained elongated grain-subgrain oriented structure in the aluminum shell and to the formation of a mixed cellular and subgrain structure in a copper core. Rotary forging leads to a significant increase in the strength of the aluminum alloy/copper bimetallic material and to a decrease in ductility. The optimal combination of increased strength and satisfactory ductility provides post-deformation annealing.

The Simulation Study on Temperature Field Distribution of 220 kV Gas Insulated Switchgear

Under working conditions, the conductive rods in the GIS flow through the power frequency alternating current. Due to the coupling effect of the magnetic field and electric field between the metal aluminum shell and the conductive rod, induced eddy currents are generated in the metal shell of the GIS. The heat generated by the current heating effect of the GIS conductive rod and the eddy current loss of the metal casing will cause the temperature rise of GIS equipment. Due to the limited volume, the heat dissipation capacity of GIS is poor. Excessive temperature rise will accelerate the insulation aging of GIS equipment, and even damage its insulation, which will affect safe operation. In order to obtain the temperature change law of GIS, related influencing factors such as eddy current loss, skin effect, proximity effect, convective heat transfer of SF6 gas, and gravity of SF6 gas are comprehensively considered. The finite element analysis is used to research and discuss GIS magnetic field distribution, eddy current, temperature distribution and SF6 gas velocity. The initial value of the temperature of each part is set to 293.15 K (20 °C), and the temperature in the GIS is calculated to gradually decrease from the inside to the outside under the rated AC current of 3150 A. The temperature at the conductive rod position is the highest at 335.32 K, and the temperature at the housing position is the lowest at 294.65 K.

Spherical Aluminum Shells (Bubbles) with Nanodimensional Wall Thickness: a New Class of 2D Nanoobjects

Spherical Aluminum Shells (Bubbles) with Nanodimensional Wall Thickness: a New Class of 2D Nanoobjects

Numerical and Experimental Investigation on Post-buckling Behavior of Stiffened Cylindrical Shells with Cutout subject to Uniform Axial Compression

In this paper, post buckling behavior of thin steel and aluminum cylindrical shells with rectangular cutouts under axial loading was studied experimentally and also using the finite element method. Riks method is used for analyzing the cylindrical shells. The effect of longitudinal and circumferential stiffeners (ribs and stringer) was studied on the buckling load and the post buckling behavior as the stiffeners used individually and in combination with each other. It was shown that by adding stringer, the buckling load improves and the rib has a positive effect on the post buckling behavior of the structure. Some tests were performed by ZwickRoell tensile/compression testing machine and it was carried out for both types of steel and aluminum shells with and without stiffeners. Comparing the experimental results with the FEA results shows good agreement. Nonlinear analysis of cylindrical steel and aluminum shells with cutout have demonstrated that, in some cases, a local buckling called snap-back can be seen in the load-displacement path. Snap-back which is a decrease in the amount of both load and displacement indicates this local buckling. This phenomenon is because of appearing mode shapes sequentially during the numerical buckling analysis of shells. Although these local buckling happened, the structure is still endured the higher loads.

Failure analysis of cracking in aluminum alloy shell of a 220 kV gas insulated switchgear

Failure analysis of cracking of a GIS aluminum shell which causes SF6 gas leak in a 220 kV substation was present. Visual inspection, microstructure observation, chemical composition and mechanical properties characterization were performed to reveal the forming mechanism of the crack. It is found that the crack is located in the region of the aluminum alloy shell that undergone welding repair. The crack is continuous and develops within the weld metal. Detailed investigation reveals that the crack initiates by the defect of lack of fusion in the welding repaired zone. The working stress induced by gas pressure, combined with the residual stress and vibration stress, results in the extension of the crack and the final leaking of SF6 gas.

Ultra-Thin Solenoid and Cryostat Development for Novel Detector Magnets

In the scope of the Future Circular electron positron Collider study (FCC-ee), the IDEA detector is developed. It comprises a superconducting solenoid with free bore of 4 m, 6 m long and a central magnetic field of 2 T. The positioning of the magnet between the inner tracker and the electronic calorimeter heavily constrains the magnet design, as it is required to have the lowest possible radiation length, so minimum thickness and lowest density material. With respect to the classical solution of a solenoid enclosing the calorimeters, a cost reduction of about 50% is expected due to size reduction. An optimization of the different components of the magnet system has been carried out, resulting in the development of a new composite high-strength conductor that can be used to build a 30 mm thin solenoid. The quench analysis of the solenoid will be presented as it is of critical importance given the high energy density in the magnet of 21 kJ/kg. A cryostat made of concentric aluminium shells would account for about 50% of the radiation length of the magnet and most of this material is used in the outer vacuum shell of the cryostat to prevent buckling. In order to further reduce the radiation length, two fundamentally different approaches are being analysed. The first method focuses on reducing drastically the outer shell thickness. This leads to use honeycomb composites, reinforcing bars and corrugated shells for the outer shell of the cryostat. The second approach consists of supporting very thin cryostat shells directly on the solenoid cold mass using proper support. This can be achieved by replacing the thick walls and MLI insulation by a material that can sustain 1 atm while having low radiation length and low thermal conductivity. Cryogel Z has shown promising properties and its suitability for this project is being analysed. This novel approach has never been used so far for superconducting magnets.

Thermal cycling aging of encapsulated phase change material – Compressed expanded natural graphite composite

A paraffin-Compressed Expanded Natural Graphite (CENG) composite encapsulated in aluminium shell has been thermally aged in a packed bed heat storage tank.A hydraulic test bed has been settled in order to impose 8500 thermal cycles where the material underwent a phase change at each cycle. The PCM phase change provokes an expansion of the composite structure that might affect the effective thermal conductivity and then the heat transfer rate of the Thermal Energy Storage (TES). This performance has been monitored all along the cycling test showing a non-significant change in heat transfer rate, despite a delamination of the composite within the capsule. This phenomenon has been explained by the delamination that affects mainly the thermal conductivity in the axial direction while the heat transfer from the PCM to the aluminium shell occurs essentially on the planar direction. Indeed, the thermal conductivity in planar direction is approximatively six times higher than on the axial direction. A DSC analysis on new and aged samples showed that the phase change temperatures remained the same and the latent heat magnitude decreased by less than 10%. A FTIR analysis confirms the chemical stability of the PCM-CENG composite after 8500 cycles.

Сравнение напряженного состояния сталемедной и сталеалюминевой биметаллических проволок

In this article, the models of steel-copper and steel-aluminum bimetallic wires obtained in the course of computer simulation in Deform program were studied, the main parameters of the stress state (equivalent stress and average hydrostatic pressure) were considered. When considering the equivalent stress, it is found that in the model with an aluminum shell, a fairly uniform distribution of stress is observed over all layers; in the model with a copper shell, due to the intensification of compression of the steel core, the stress distribution in both layers is extremely uneven – in the shell, the stress level decreases sharply in the direction from the outer layers to the inner ones. When considering the average hydrostatic pressure, it is found that when the aluminum shell changes to copper, the hydrostatic pressure in both layers increases in absolute values, which is a consequence of an increase in the overall level of deformation resistance.