Aluminum Alloy Specimens Research Articles

Computer Simulation of Heating Cycle of Aluminum Alloys Using Friction Stir Welding Technology

The paper deals with welding of aluminum alloys using Friction Stir Welding technology. This repre-sents one of the solid-state welding technologies in which the base materials are not melted. This pro-vides new possibilities for the use of special and hybrid manufacturing technologies. The article presents the current progress in the Friction Stir Welding technology, a microstructure analysis of a weld joint created by the FSW method and a heat-deformation computer simulation of an aluminium alloy speci-men in the program Ansys.

Analysis of Inclined Crack in Aluminium Alloy Plate Subjected to Three-Point Bending Load Repaired with Carbon Fiber Reinforced Polymer

If the attention is not paid to the crack in a structure, then it could suddenly propagate at a rapid rate and rip apart the structures. A small crack needs urgent attention and repair since replacing the parts with a small crack is not economically feasible at all the time. Repairs were used to be carried out through rivets, welding and nut-bolts, but recently composite materials are showing promising results in this field. Since composite material are anisotropic in nature their application needs careful study about the loading pattern on the repaired structure. In this study, Carbon Fiber Reinforced Polymer (CFRP) was used as a composite material to repair Aluminium alloy specimens. These specimen were subjected to a three-point bending load to investigate the effectiveness of CFRP. By using innovative ply drop technique and design of experiment a configuration was selected to sustain three-point bending load. To suppress the CFRP’s peeling off tendency, attention was given to the interfacial shear stress rather than to the fracture toughness parameter.

Optimisation of Rayleigh wave Laser-EMAT with the application of surface constraint mechanism

ABSTRACT A laser-electromagnetic acoustic transducer (Laser-EMAT) Rayleigh wave (RW) detection based on surface constraint mechanism and its optimisation design are proposed to solve the low signal-to-noise ratio (SNR) of its application in aluminium alloy detection at high-temperature. We established a finite element (FE) model of aluminium alloy’s Laser-EMAT RW detection process based on the surface constraint mechanism and investigated the effect of the surface constraint mechanism on laser-excited RW . We also studied the effects of laser parameters and meander-line coil (MLC) EMAT parameters on the ultrasonic wave amplitude and spectral composition. Finally, the enhancement effect of the surface constraint mechanism on RW amplitude was analysed by Laser-EMAT RW detection experiments on aluminium alloy at room temperature and high temperatures. The results show that the optimised MLC-EMAT can increase the RW amplitude by 1.97 times. When the laser line source width equals the MLC-EMAT turn spacing, the echo SNR is the highest. The enhancement effect of the surface constraint mechanism on the RW amplitude gradually decreasesas the specimen temperature increases. The RW amplitude can increase by 1.43 times when the surface constraint mechanism is applied at room temperature, and for the aluminium alloy specimen at 430°C, the RW amplitude can increase by 32%.

Study on the Fracture Behaviour of 6061 Aluminum Alloy Extruded Tube during Different Stress Conditions

To study the deformation and fracture mechanism of 6061 aluminum alloy extruded pipe after secondary heat treatment under different stress triaxiality, a Johnson–Cook failure model was developed. Through the FEM method and SEM, the fracture mechanism of different types of aluminum alloy tensile specimens was analyzed. The research results show that the Johnson–Cook failure model could better simulate the tensile deformation of 6061 aluminum alloy specimens of different types, the parameters of the Johnson–Cook failure model were finally obtained D1 = 0.29, D2 = 1.356, and D3 = −2.567. With the increase of the stress triaxiality, the fracture strain showed a decreasing trend as a whole, and the fracture mechanism changed from a shear type to a hole aggregation type. The stress triaxiality gradually decreased with the increase of the notch radius/angles of the aluminum alloy notch specimen, and the stress triaxiality at the center of the notch was higher than the stress triaxiality at the root of the notch.

Quantifying combined effects of in-plane and out-of-plane constraint in an aluminium alloy

Fracture load of a component can depend on the geometry as well as the material properties due to the effect of constraint on the plastic region which forms around the crack tip prior to fracture. The constraint has two components: in-plane constraint, due to the size and geometry of the component, and out-of-plane constraint, mainly due to its thickness but also affected by other geometric parameters. There are currently methods to quantify both types of constraint separately as well as suggested parameters that quantify both simultaneously. However, experimental programmes that objectively compare the applicability of each are few and far between, especially on the out-of-plane constraint. In this paper we report the results of a substantial experimental programme making use of single edge notched bend (SENB) aluminium alloy specimens to study the combined effects of in-plane and out-of-plane constraint. These experiments involved testing the specimens in a three-point bending configuration with nine combinations of thickness and crack length. This allowed fracture loads to be measured then converted to stress intensity factor K by the use of three-dimensional finite element simulations. Common constraint parameters such as the Q parameter and plastic zone volume were extracted from these simulations. The results showed that K varied between 31 and 55 MPa√m for various levels of in and out-of-plane constraint. Both the magnitude of Q and the plastic zone volume increase with reducing plastic constraint. We showed that both Q and plastic zone volume could be used to quantify the combined effects of in and out-of-plane constraint, however the uncertainty associated with the plastic zone volume is less than that of Q.

Laser ultrasonic imaging of subsurface defects with the linear sampling method.

Laser ultrasonics is a remote nondestructive evaluation technique suitable for real-time monitoring of fabrication processes in semiconductor metrology, advanced manufacturing, and other applications where non-contact, high fidelity measurements are required. Here we investigate laser ultrasonic data processing approaches to reconstruct images of subsurface side drilled holes in aluminum alloy specimens. We demonstrate through simulation that the model-based linear sampling method (LSM) can perform accurate shape reconstruction of single and multiple holes and produce images with well-defined boundaries. We experimentally confirm that LSM produces images that represent the internal geometric features of an object, some of which may be missed by conventional imaging.

Mechanical properties and microstructure characteristics of 2024-T351 aluminum alloy specimen subjected to paint removal by laser cleaning

In this work, the mechanical properties and microstructure characteristics of 2024-T351 aluminum alloy specimen subjected to paint removal by laser cleaning were explored. The measurement of surface microhardness and tensile properties of the samples were performed before and after laser cleaning. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to inspect the microstructural characteristics. Compared with the untreated sample, the results of experiment indicated that the surface microhardness and tensile strength of the specimen treated by laser clearing increased by 10.6% and 8.4%, respectively. Additionally, grain refinement and dislocation proliferation induced in the laser cleaning process have a critical contribution to enhancing the microhardness and tensile properties of 2024-T351 aluminum alloy.

Mesoscopic defect healing and fatigue lifetime improvement of 6061-T6 aluminum alloy by electropulsing treatment

Defect healing through pulsed electric current treatment is an important work worthy of further discussion. 6061-T6 aluminum alloy specimens were subjected to the fatigue loading and pulsed electric current treatment. Then mesoscopic defect features inside 6061-T6 aluminum alloy before and after applying electric pulses were analyzed through X-ray microcomputer tomography and 3D reconstruction software VGSTUDIO MAX. The influence weights of pulsed electric current on the mesoscopic defect were obtained by principal component analysis based on the reduction rate of defect feature parameters. A parametric model was established to obtain the defect information of pulse current healing based on the influence weights obtained. The fatigue life prediction is carried out using this model, and the verification is conducted by experiment work.

Corrosive effect of powder and granular fluxes on structural materials

This paper describes the results of a study that looked at the effect produced by powder and granular fluxes on specimens of aluminium alloy 6063 and steel St3 in a corrosive environment. The authors simulated the use of the above fluxes in a production environment by transferring the flux samples from one container to the other close to the specimens. After simulation, the specimens were inspected visually and weighed. Thus, in the case of granular flux its finedispersed particles were observed on ~8% of the specimens’ surface, while in the case of powder flux almost the entire surface of the specimens was covered with its particles. The corrosive effect of the deposited flux particles was analyzed by placing the specimens in a climatizer with high humidity and temperature. The conducted studies showed that the use of granular flux is associated with a smaller amount of fine-dispersed flux particles deposited on the specimen surface. The results of the climatizer study suggest that the corrosion rate of structural materials should be twice or more higher when using powder flux than when using flux granules.

A Compensation Algorithm for Large Element Characterizing the Damage Evolution Process and Its Application to Structure Collisions

When simulating the process from elastic–plastic deformation, damage to failure in a metal structure collision, it is necessary to use the large shell element due to the calculation efficiency, but this would affect the accuracy of damage evolution simulation. The compensation algorithm adjusting failure strain according to element size is usually used in the damage model to deal with the problem. In this paper, a new nonlinear compensation algorithm between failure strain and element size was proposed, which was incorporated in the damage model GISSMO (Generalized incremental stress state dependent damage model) to characterize ductile fracture. And associated material parameters were calibrated based on tensile experiments of aluminum alloy specimens with notches. Simulation and experimental results show that the new compensation algorithm significantly reduces the dependence of element size compared with the constant failure strain model and the damage model with the linear compensation algorithm. During the axial splitting process of a circular tubular structure, the new compensation algorithm keeps the failure prediction errors low over the stress states ranging from shear to biaxial tension, and achieves the objective prediction of the damage evolution process. This study demonstrates how the compensation algorithm resolves the contradiction between large element size and fracture prediction accuracy, and this facilitates the use of the damage model in ductile fracture prediction for engineering structures.

A Study on the Fatigue Life of the Laser Additive Manufactured Metallic Material

As more and more structural parts of military aircraft are formed with additive manufacturing (AM) technology, it was very urgent to study fatigue characteristics of additive manufacturing materials and structures. In order to study the fatigue life characteristics of aluminum alloy and titanium alloy manufactured by selective laser melting (SLM), a series of specimens with various structural details were designed and tested under constant amplitude and random spectrum. The basic reliability life of each test results was statistically analyzed and the reliability safety life curve was obtained. Fractography analysis showed that there were more defects and mixed failure characteristics in aluminum alloy specimens, while the fatigue-scatter of titanium alloy counterpart was larger than that of forgings.

Study on the surface integrity of 7050 aluminum alloy with different crystal orientations during high-speed machining

This paper investigates the effect of crystal orientations and machining parameters on the surface integrity of 7050 aluminum alloy in high-speed machining. Three groups of pre-compression deformations (10%, 15%, and 20%) are performed on the aluminum alloy to fabricate specimens with different crystal orientations. A single-factor dry-cutting experiment was designed, and the surface roughness, surface morphology and defects, work hardening, and X-ray diffraction (XRD) were tested. The results show that the 15% pre-deformed 7050 aluminum alloy specimen had lower surface roughness and the best surface quality under the same cutting parameters. The surface roughness of 7050 aluminum alloy with different crystal orientations tended to first increase and then decrease with the increase of the cutting speed, and the surface roughness was positively correlated with the cutting depth and feed rate. Under different cutting parameters, the machined surfaces of 7050 aluminum alloy specimens with different crystal orientations exhibited different degrees of plowings, apophysis, sticky chips, and pits. Moreover, the degree of work hardening of the 15% pre-deformed 7050 aluminum alloy specimen was small, while that of the 20% pre-deformed specimen was more serious. XRD analysis demonstrated that the diffraction peak width of the 10% pre-deformed 7050 aluminum alloy specimen slightly increased with the increase of the cutting depth. Moreover, the (111) and (200) diffraction peak intensities of the 15% pre-deformed 7050 aluminum alloy specimen increased with the increase of the cutting speed, and there was no obvious Al2CuMg phase on the machined surface of the 20% pre-deformed specimen.

Drilling Strategies to Improve the Geometrical and Dimensional Accuracy of Deep through Holes Made in PA6 Alloy.

This article shows how different drilling strategies may affect the geometrical and dimensional accuracy of deep through holes. The tests were conducted on a three-axis direct-drive turning center. The holes were drilled in cylindrical PA6 aluminum alloy specimens 30 mm in length and 30 mm in diameter using 6 mm Ø VHM HPC TiAlN-coated twist drill bits. The cutting fluid was supplied to the cutting zone through the spindle. The experiments involved applying three strategies to drill deep through (5D) holes. The first required the workpiece to be fixed and the tool to perform both rotary and reciprocating motions. The second assumed that the workpiece performed the primary (rotary) motion whereas the tool moved in reciprocating motion. In the third strategy, the workpiece and the tool rotated in opposite directions and the tool also performed a reciprocating motion. The straightness, roundness, cylindricity, and diameter errors were the key output parameters in the analysis of the geometrical and dimensional accuracy of holes. The Taguchi orthogonal array design of experiment (DOE) was employed to determine the effects of the input (cutting) parameters (i.e., spindle speed and feed per revolution) and the type of hole making strategy on the hole errors by means of multi-factor statistical analysis ANOVA. The use of the highest spindle speed (n = 4775 rpm), the highest feed per revolution (fn = 0.14 mm/rev) and strategy I resulted in the lowest values of the output parameters (STR = 22.7 µm, RON = 8.6 µm, CYL = 28.2 µm, and DE = 9.9 µm). Strategy I was reported to be the most effective for hole drilling in PA6 aluminum alloy because, irrespective of the values of the process parameters used, three out of four output parameters, i.e., straightness, roundness and diameter errors, reached the lowest values.

Acceleration factor and experimental validation of aluminum alloy under narrow‐band random excitation

AbstractIn order to reduce the vibration fatigue test time of aeronautical engineering components made of aluminum alloy, a random vibration fatigue acceleration model under narrow‐band excitation is proposed in this paper. A three‐parameter S–N curve is adopted to consider the effect of small stress response, while a scale factor α is introduced to consider the effect of stress distribution. The random vibration fatigue tests of 2024‐T3 and 7075‐T6 aluminum alloy specimens with elliptical holes are performed, where the vibration fatigue lives of load spectra with the same bandwidth and different excitation acceleration levels are obtained. The test results show that the proposed model is in sound agreement with the test results.

Experimental and numerical studies on lateral low-velocity impact behaviour and residual axial strength of circular aluminum alloy (6061-T6) tubes

Aluminum alloy (6061-T6) is commonly used in engineering applications owing to its lightweight, anti-corrosion, and good plasticity, such as the reticular space structure of the Interamerican Exhibition Center of Sao Paulo in Brazil, Sport Hall of Quito in Ecuador and the Memorial Pyramid in La Baie in Canada. Herein, the typical impact process of aluminum alloy (6061-T6) under lateral low-velocity impact were investigated through experiments and simulations. A drop-weight test fixture was used for lateral impact experiments, considering the influence of span length, tube thickness, diameter, impact kinetic energy, impact momentum, and impact position. The plastic deformation and failure modes of the aluminum alloy (6061-T6) specimens subjected to different impact conditions were studied after the experiments. Four types of failure patterns are described according to the three-hinge mechanism. Quasi-static tensile tests were performed to calibrate the constitutive parameters using the Johnson-Cook model. Meanwhile, a finite element (FE) model of circular aluminum alloy tubes verified the results of the impact test and to analyze the evolution of the dynamic failure. The simulation results were used to analyze the plastic global displacement and energy dissipation. The concepts of both global lateral stiffness and local lateral stiffness were proposed, and two types of energy dissipation modes were described. In addition, the study considered the residual axial strength of the specimens after low-velocity impact. A residual performance model was developed to analyze the effects of span length, wall thickness, and various factors. Finally, a calculation formula was proposed to predict the residual axial strength based on the simulation results.

Study of Tensile Strength of Aluminum Alloy Caused by Pulsed Laser Drilling

In the process of pulsed laser drilling, the material properties in the heat-affected zone will change due to the thermal effect of the laser. To study the effect of this change on the material tensile strength, two lasers were used to punch the standard 6061 aluminum alloy specimens with millisecond and nanosecond pulse widths, and then the tensile test was carried out on the standard specimens with a tensile tester to measure the ultimate tensile strength of the aluminum alloy. Finally, the micro-morphology of the fracture was photographed by scanning electron microscopy (SEM), and the fracture mechanism of the aluminum alloy was analyzed. The experimental results show that the relationship between the rate of intensity change induced by the millisecond laser and the ablation area ratio is more linear than that of the nanosecond laser; with the increase of ablation area ratio, the rate of intensity changes induced by the nanosecond and millisecond lasers becomes increasingly closer; three types of fractures are produced with two types of laser ablation; the plasticity of the material rapidly decreases with laser drilling, and the main reason for decrease in plasticity was stress concentration. This study provides an important point of reference for how to ensure the strength and plasticity of the components after laser drilling.

Microstructure and residual stress modulation of 7075 aluminum alloy for improving fatigue performance by laser shock peening

Laser shock peening (LSP) is an advanced surface-strengthening technology that improves the anti-fatigue performance of metallic components. However, there is a significant barrier to the application of thin-walled components because the high-energy laser causes deformation and nonuniformity of compressive residual stress, thereby reducing fatigue performance. In this study, an LSP technology based on a low-pulse-energy laser was developed. We applied it to a thin-walled AA7075 aluminium alloy specimen (∼4 mm thickness) and achieved an improvement in the high-cycle fatigue limit of 20.4 and 37.0% for the smooth and pre-cracked fatigue specimens, respectively, in the absence of deformation. It was discovered that the enhanced dynamic nanoscale precipitation and dislocation multiplication effects of the high-pressure shock wave contribute to microstructure stability under cyclic loading, resulting in high compressive residual stress stability. Moreover, the unique heterogeneous grain structure on the surface layer subjected to LSP at low pulse energy effectively restrains crack initiation and propagation. Because these findings apply to a wide range of alloys, the current results create new avenues for improving the fatigue performance of thin-walled components.

Pitting corrosion behavior and mechanism of 5083 aluminum alloy based on dry‐wet cycle exposure

AbstractElectrochemical and surface analysis methods were used to investigate the pitting susceptibility and propagation of as‐received and dry‐wet cycle exposed 5083 aluminum alloy (AA5083) specimens. We find that dry‐wet cycle exposure can reduce the corrosion potential, while increasing the corrosion current density, pitting potential (Ep), and passivation range. The pitting corrosion behavior during the dry‐wet cycle process depends on the exposure temperature and time. Increased exposure temperature and time result in reduced pitting percentage and corrosion altitude and decreased microhardness of the corrosion products, which promotes the pitting sensitivity of AA5083. The underlying pitting mechanism is proposed by employing the morphology and microstructures of the corrosion products.

The effect of surface treatment on the shear properties of aluminium-polypropylene joints manufactured by laser beam

In this article, we evaluated the mechanical response of laser-joined EN AW-6082 aluminium alloy and polypropylene (PP) specimens under quasi-static and cyclic shear loading. In order to increase the strength of the joints, we formed grooves in the aluminium with laser ablation. We determined the effect of PP melt viscosity and heat generated during the joining process on the shear strength of the joints using three types of PP with different melt viscosities. In order to influence the adhesion between the apolar polypropylene and the aluminium, we also treated some PP specimens with maleic anhydride (MA) prior to joint formation. We found that by doing so, the quasi-static shear strength of the joints increased by 50% on average. Furthermore, when we engraved many grooves in the aluminium and treated the PP specimens with MA, the average failure cycle number of specimens could be increased by an order of magnitude.

Study of dynamic mechanical behavior of 1060-H112 aluminum alloy: Experimental and numerical simulation

1060-H112 aluminum alloy with high ductility is widely used in industrial engineering. The study of its dynamic mechanical behavior has theoretical and engineering application value. In this paper, quasi-static tensile tests from room temperature to 250°C and high strain rate compression tests were conducted using a universal material testing machine and a Hopkinson compression bar. By using a hybrid test-numerical simulation method, a modified Johnson-Cook (MJC) strength model and Cockcroft-Latham (C-L) fracture criterion parameters were calibrated. Subsequently, Taylor impact tests were performed on 1060-H112 aluminum alloy specimens with a diameter of 12.66 mm and a length of 50.64 mm in the range of 176.3–483.03 m/s. Upsetting and tensile tearing were observed in the tests. A 12.68 mm diameter blunt nosed projectile impact test on 2 mm 1060-H112 aluminum alloy plate was also conducted with a light gas gun system, and the speed related parameters and failure modes were obtained. Finally, a three-dimensional model corresponding to the test was established in ABAQUS/Explicit finite element simulation software, and the failure modes of the Taylor rod and the velocity parameters and failure modes of the target impact test were predicted. The results show that the MJC strength model and the C-L fracture criterion can predict the experimental results of the two tests accurately. It shows that the MJC strength model and C-L fracture criterion have high accuracy, and they will play an important role in the application of 1060-H112 aluminum alloy in industrial engineering.