Aluminum Strips Research Articles

Experimental Study of Bimaterial Shear Strength and Strain Concentrations by Iosipescu Based Test Using Digital Image Correlation System

Adhesive bonding of two different materials appears in many modern engineering applications, e.g.: airplanes, boats, cars etc. In many practical problems the adhesive bonding is subjected to shear loading. Therefore this is important to investigate the whole deformation process of the considered type of joints under monotonic loading, to get information about the shear strength and strain concentrations. Such concentrations lead to microdefects initiation and their further coalescence to create a main crack. The unstable crack propagation leads to final failure of the adhesive joint. The Digital Image Correlation (DIC) System - ARAMIS allows for constant monitoring of the deformation state up to the final failure. The tests were performed for bi-material specimens made of adhesively bonded PMMA and aluminum strips (Fig.1) and for pure PMMA and pure aluminum specimens. Additionally, two strain gauges on each homogeneous specimen and four on the bimaterial ones are used for strains estimations. The four point bending Iosipescu tests were performed using MTS machine with constant speed. In the first method (DIC) the ARAMIS system recorded a displacement distribution in samples with frequency 1Hz. In the second method the strains were recorded by the strain gauges - using analog output channels of the HOTTINGER data Acquisition System - MGCPlus, the current value of the load using analog output channel of the MTS machine was recorded too. The load-displacement curves were obtained for the whole deformation process and the shear strength of the joints was estimated. The energy absorption of the joints was calculated.

The influence of TiO2 nano-particles on bond strength of cold roll bonded aluminum strips

Abstract In the present work, cold roll bonding (CRB) process characteristics of AA1050 strips, such as bond strength, threshold deformation, undulation of peeling force, and peeled surface in the presence of TiO 2 nano-particles were carried out and compared to those of aluminum strip without particles. The bond strength was evaluated by the peeling test. The results indicated that when the reduction in thickness was increased, the peeling force of AA1050 strips was enhanced. It was found that the presence of TiO 2 nano-particles reduces the bond strength of layered strips when compared to layered pure aluminum for the same reduction in thickness applied through CRB process. When the reduction in thickness was increased, the undulation of average peeling force values was increased at constant particles content. Also, the strips without particles had lower undulation value as compared to the strips with titanium oxide particles. In addition, in the presence of titanium oxide, when the particles content was increased, the undulation of average peeling force values was decreased at constant reduction in thickness. On the other hand, by increasing the particles content, the average slope of bond strength curves was decreased and the threshold deformation was increased. Finally, it was found that the bond strength of AA1100/alumina/AA1100 strips was much more than that of AA1050/titanium oxide/AA1050. This was attributed to both the metal and particle type.

Effects of temperature and B4C content on the bonding properties of roll-bonded aluminum strips

The presence of ceramic particles between metal strips in metal matrix composite processing by roll bonding affects their bonding properties. In this study, roll bonding of commercial pure aluminum (AA1100) strips in the presence of various B4C contents at different thickness reductions was focused. Furthermore, the effect of rolling temperature (at ambient temperature and 473 K) on the bonding properties of the strips was investigated via peeling tests. The results showed that the presence of the B4C particles between the aluminum strips reduces the bond strength and weld efficiency; in contrast, they are increased by increasing temperature. Therefore, by increasing temperature it is possible to use the higher amounts of the B4C particles between the aluminum strips.

Influence of Punch Velocity on Spring Back in Micro Forming

In macro forming it is already known, that the punch velocity has an influence on the deep drawing process. This influence is considerably induced by the velocity dependent friction behavior between sample and tool. A further influence is the strain rate dependent forming behavior of the material. In micro range, the influence of punch velocity on the deep drawing process could, due to the size effects, be different from that in macro range, for example the spring back behavior. In this article the influence of punch velocity on the spring back behavior in micro deep drawing is investigated using strip drawing test with two different widths (1 mm and 2 mm). Experiments with aluminum strips with a thickness of 50 µm were performed with punch velocities ranged from 1 mm/s to 1000 mm/s. The strain behavior, which occurs with different punch velocities are investigated on the basis of microsections. The spring back of all samples was measured by an optical measurement system and compared with each other. From the reported work it can be concluded, that with increasing punch velocity the spring back of the complete system is increasing, while the spring back at cup wall stays constant. As reasons can be cited mass inertia effects due to the high velocities and the velocity dependent friction.

Prediction on Transverse Thickness of Hot Rolling Aluminum Strip Based on BP Neural Network

For aluminum hot rolling process with multi-variables, strongly coupling, nonlinear, it is difficult to establish accurate mathematical model to solve transverse thickness distribution. A method based on BP neural network with hot rolling aluminum transverse thickness prediction was proposed; According to multi-channel measurement characteristics of IMS transverse thickness collection system, the BP neural network prediction model for single channel was established; predicting every channel thickness by BP neural network, transverse thickness distribution of aluminum strip was obtained. Simulation results compared with the measured datas, the relative error is less than 2.5%. The results indicate that the BP neural network is suitable for transverse thickness prediction of hot rolling aluminum strip.

Evaluation of diffusion and phase transformation at Ag/Al bimetal produced by cold roll welding

Aluminum and silver strips were cold welded by rolling and a bimetallic strip was produced. To create cold weld between Al and Ag, mating surfaces were specially prepared and various rolling thickness reductions were applied. The minimum critical thickness reduction to begin cold weld was specified as 70% which equals 0.1630 critical rolling shape factors. The bimetallic strips were treated by diffusion annealing at 400 °C and various annealing time. The Al/Ag interface of strips was observed by scanning electron microscope to investigate the formation of hard and brittle probable phases. The effect of anneal time on diffusion distance and phase transformation was also analysed by EDS analysis and line scan. A diffusion region along the interface in the Ag side was observed and its width increased with prolonging annealing time. Some δ phases were detected close to the interface after anneal treating for 3 h and δ phase was thicker and more continuous by increasing annealing time. The microhardness measurement showed that in spite of formation of δ phase due to diffusion annealing, the interface hardness was reduced.

Measurement of the M-integral for a Hole in an Aluminum Plate or Strip

A method using Digital Image Correlation (DIC) is proposed to measure the M-integral in an elastic rectangular plate and elastic–plastic strip made of LY12 Aluminum where a hole is located at center as a defect. The path-independence property of the M-integral is verified by selecting a few of closed contours to evaluate the M-integral. It is found that the measured values of the M-integral are path-independent when the closed contours are far from the nonlinear plastic zone. In contrast, large deviations occur in determining the M-integral among different integral contours when the contours pass through the plastic zone. The present study demonstrates that DIC method used by the ARAMIS 4 M instrument and the proposed smoothing technique for evaluating the measured displacements do provide the effective tools to measure the M-integral in describing the local damage of elastic and elastic–plastic materials. This technique could be extended to measure the M-integral for other complicated damage, e.g., multiple defects with different shapes in a local region.

Influence of temperature and humidity on the degradation process of ascorbic acid in vitamin C chewable tablets

Ascorbic acid (AA) is the active ingredient of vitamin C chewable tablets. It is unstable even at room temperature, and increased temperature and humidity rapidly increase its degradation. To protect the active substance, we made its coating with polymers ethyl cellulose that provides its thermal protection and protection from moisture. We bet each particle of AA with a layer of polymer by the method of fluidization. Extra protection against thermal effects and penetration of moisture and oxygen provides the packaging. By using four kinds of packaging: polypropylene container for tablets, strips of aluminum and polyvinyl chloride Al/PVC strips, glass bottles, and strips of aluminum and polyethylene (Al.PE/PE.Al) of 3, of 6 months and of 12 months. One of the tablets are stored at room temperature (25 ± 2 °C/60% RH ± 5%), and the rest in terms of accelerated aging or increased temperature and humidity (30 ± 2 °C/65% RH ± 5% and 40 ± 2 °C/75% RH ± 5%). The speed of degradation of unprotected AA usually get doubled when there is increasing of the temperature for every 10 °C. Experimentally the concentration of AA was monitored, its oxidation product-dehydroascorbic acid and its degradation product-diketogulonic acid.

Effect of SiC particles on the microstructure evolution and mechanical properties of aluminum during ARB process

Abstract The effect of the addition of SiC particles on the microstructural evolution and mechanical properties of aluminum strips during accumulative roll bonding (ARB) was studied. Nanostructured Al/7 vol.% SiC p composite sheets were produced by ARB at room temperature. Monolithic Al sheets were also produced by the ARB process to compare with the composite samples. The fabricated composites after 8 ARB cycles showed a fairly homogeneous distribution of the SiC particles without significant porosities. Elongated ultrafine grains were formed in the ARB processed specimens of both the monolithic Al and Al/SiC p composite. It was found that the grain refinement is accelerated by the presence of the SiC particles, so that the Al matrix of the ARB processed composite showed finer grain sizes with the higher fraction of high-angle grain boundaries than the monolithic Al specimen. It was also found that the tensile strength of the ultrafine grained Al/SiC p composite was about 1.33 times higher than that of the ultrafine grained monolithic aluminum.

Planarization of inhomogeneous structures by means of physical ion sputtering

The dynamics of ion-beam etching of test microstructures, simulating fragments of the surface structure of very large-scale modern integrated circuits, has been studied. Aluminum strip microstructures, 0.5 μm high and 1 μm wide deposited on the surface or embedded into SiO2, were used as test samples. 1 keV Ar+ ion beam 1 with a current density 0.5 mA/cm2, incident on the surface of a sample, rotating at a speed of 60 r/min, at an angle of 87°, has been used in the experiments. The surface morphology evolution was studied using atomic-force microscopy. The experiments demonstrate that physical ion sputtering at glancing incident angles can be used for the planarization of originally inhomogeneous structures. The achieved planarization degree allows one to use this method for defect detection in the metallization multilevel layers of very large-scale modern integrated circuits.

Chaos Character of Deviation Signal and Prediction of Tail Deviation in Strip's Rolling

In strip tandem rolling process, there is always deviation between the center line of the strip and the assumed center line, which is called running deviation. In this thesis, based on the actual running deviation data of some aluminum strip rolling industry, we analyzed their chaos and fractal character, proposed one improved pattern classification based on the fuzzy c-average clustering, on basis of this method classified running deviation pattern, constructed adding weight zero-order local prediction method of strip truning deviation signal. After the s actual data test, the forecasting result achieves the desired accuracy.

Microstructure and mechanical properties of Al/SiO2 composite produced by CAR process

Continual annealing and roll-bonding (CAR) process was used in this study as a very effective method for fabrication of the Al/15 vol.% SiO2 metal matrix composite. The microstructure of the produced composites after 6 cycles of the CAR process was showed an excellent distribution of SiO2 particles in the AA1100 matrix without any porosity. Particle breaking was one of the most important phenomena that can occur in CAR process. The results also were indicated that when the number of CAR cycle was increased, the tensile strength of the manufactured composites was improved, but their elongation was decreased at first step and then was increased. The tensile strength of the composite was 1.77 and 1.63 times higher than the same values was obtained for annealed and monolithic aluminum strips, respectively, while the elongation value was decreased slightly.

Microstructure and mechanical properties of Al/Al2O3 MMC produced by anodising and cold roll bonding

In the present paper, Al–Al2O3 composite strips are produced by the cold roll bonding process of anodised aluminium strips. This technique has the flexibility to control the volume fraction of metal matrix composites by varying the oxide layer thickness on the anodised aluminium strip. Microhardness, tensile strength and elongation of composite strips are investigated as a function of quantity of alumina and the applied production method. It is found that higher quantities of alumina improve microhardness and tensile strength, while the elongation value decreases negligibly. Furthermore, prerolling annealing is found to be the best method of producing this composite via the cold roll bonding process. Finally, it is found that both monolithic aluminium and aluminium/alumina composite exhibited a ductile fracture, having dimples and shear zones.

Investigation of Stress Effect of Electromigration Behavior of Aluminum Strip

The unpassivated aluminum thin film test specimens and the four-point-bend equipment have been successfully fabricated and developed to investigate the thermal and external mechanical stress impacts during the electromigration (EM) test. This paper found that once the thin films reach equilibrium after the EM test, the aluminum atomic concentration, originally at 74%, decreases to about 60% at the cathode and increases up to about 80% at the anode. In addition, this paper observed that an incubation stage is present during the EM test. In this stage, no drift will take place. This result observed that the incubation stage in this paper is 2 h. Under the external mechanical stress range of -50 to +50 MPa, it was observed that the higher the tensile stress applied, the shorter the critical length becomes.

Variation of texture parameters in treatment of strip of aluminum and copper alloys and relationship between texture parameters and physical properties

Texture parameters that have been proposed for control of the mechanical properties and ductility anisotropy of sheet face-centered cubic alloys, their variation in the course of manufacture, and relationship to the quality characteristics are investigated. The efficiency of active control in an on-line regime with continuous heat treatment of the alloys to bring the alloys to a state of incomplete primary recrystallization which will alters the texture of the rolled product accompanied by the formation of different orientations with the plane {100} in the rolling plane, in particular, cubic orientations, is determined. Astrategy for the use of active texture control is developed and the limits of its effective application are defined.

Aluminum Hot Finishing Rolling Process Parameters on the Effect of Temperature Field Distribution

According to actual structure parameters and the technological parameters in an aluminum hot rolling production line, consider the rolling of metal plastic deformation heat, the contact surface heat conductivity, friction heat effect on the rolled piece and the roller heat transfer, use finite element analysis software MSC.Marc to build thermo-mechanical coupled finite element simulation model about aluminum hot rolling frame F2. Analyzing different rolling process parameters on the influence of the temperature field distribution regularity, and by adjusting the rolled-piece technology parameters to control temperature distribution, so as to achieve the purpose of improving product quality, and to provide theoretical basis for production of aluminum strip.

Cryogenic reliability of composite insulation panels for liquefied natural gas (LNG) ships

The major carrier of liquefied natural gas (LNG) is LNG ships, whose containment system is composed of dual barriers and composite insulation panels. The LNG containment system should have cryogenic reliability and high thermal insulation performance for safe and efficient transportation of LNG. The secondary barrier composed of adhesive bonded aluminum strips should keep tightness for 15 days, when the welded stainless primary barrier fails. However, cracks are generated in the composite insulation panels due to the local stress concentration and the brittleness of insulation materials at the cryogenic temperature of −163 °C. If cracks generated in the insulation panel propagate into the secondary barrier, LNG leakage problem might occur, which is a remaining concern in ship building industries. In this study, crack retardation capability in the composite insulation panel was investigated with glass fabric reinforcement. Finite element analysis was conducted to estimate the thermal stress at the cryogenic temperature and a new experimental method was developed to investigate the failure of secondary barrier of composite insulation panel. From the experimental results, it was found that the glass fabric reinforcement was effective to retard the crack propagation into the aluminum secondary barrier from the polyurethane insulation foam at the cryogenic temperature.

Inhomogeneity of temperature distribution through thickness of the aluminium strip during hot rolling

Temperature distribution and inhomogeneity of its through thickness of the strip play an essential role in hot rolling processes, where both the strip and work-roll behaviour are affected strongly by these temperature fields and the microstructural and mechanical properties through thickness of hot rolled strip depend on this temperature inhomogeneity within the strip being deformed during hot rolling. In this investigation, a mathematical model was developed to predict the thermal history and inhomogeneity of temperature through thickness of an aluminium alloy strip undergoing single-stand hot plate rolling using the commercial finite element (FE) package, ABAQUS/Explicit in three dimensions. To estimate the reliability of the numerical analysis, the FE model was validated using experimental roll force and torque data and also temperature history at the centre-line of strip; good agreement was found between the two sets of predicated and experimental results. The effects of various process parameters, such as rolling speed, interface heat-transfer and friction coefficients between strip and work roll, initial thickness of the strip, and work-roll temperature and diameter on the temperature inhomogeneity, is considered.

Shot peening and peen forming finite element modelling – Towards a quantitative method

Peen forming is commonly used on aluminium alloys in the aerospace industry for wing skin shaping. Numerous analytical, numerical, and experimental studies have been made to better understand the effects of various peening parameters on the final material state and to predict deformed shapes, but conclusions were often limited to trends. The purpose of this study is therefore to develop and verify experimentally quantitative numerical tools for peen forming applications by studying the simple case of peening an Almen-sized AA-2024 aluminium strip in an Almen holder. The first step consisted in improving an existing random dynamic model by determining optimal dimensions. The AA-2024 target mechanical behaviour was characterized experimentally and a combined isotropic-kinematic hardening law was selected to model the material behaviour. The dynamic impact model and material constitutive law provided good prediction of peening-induced stresses in thick AA-2024 for two shot velocities. The sequence-sensitive aspect of the forming process was also investigated and a new shell-based finite element model was proposed. Numerical and experimental results for three shot velocities were compared to evaluate the validity of this numerical simulation method and promising agreement was observed.

Power Stored and Quality Factors in Frequency Selective Surfaces at THz Frequencies

A study of the external, loaded and unloaded quality factors for frequency selective surfaces (FSSs) is presented. The study is focused on THz frequencies between 5 and 30 THz, where ohmic losses arising from the conductors become important. The influence of material properties, such as metal thickness, conductivity dispersion and surface roughness, is investigated. An equivalent circuit that models the FSS in the presence of ohmic losses is introduced and validated by means of full-wave results. Using both full-wave methods as well as a circuit model, the reactive energy stored in the vicinity of the FSS at resonance upon plane-wave incidence is presented. By studying a doubly periodic array of aluminium strips, it is revealed that the reactive power stored at resonance increases rapidly with increasing periodicity. Moreover, it is demonstrated that arrays with larger periodicity-and therefore less metallisation per unit area-exhibit stronger thermal absorption. Despite this absorption, arrays with higher periodicities produce higher unloaded quality factors. Finally, experimental results of a fabricated prototype operating at 14 THz are presented.