6061-T6 Aluminum Research Articles

Enhancing Friction Stir Welding in Fishing Boat Construction through Deep Learning-Based Optimization

In the present study, the authors have attempted to present a novel approach for the prediction, analysis, and optimization of the Friction Stir Welding (FSW) process based on the Deep Neural Network (DNN) model. To obtain the DNN structure with high accuracy, the most focus has been on the number of hidden layers and the activation functions. The DNN was developed by a small database containing results of tensile and hardness tests of welded 7075-T6 aluminum alloy. This material and the production method were selected based on the application in the construction of fishing boat flooring, because on the one hand, it faces the corrosion caused by proximity to sea water and on the other hand, due to direct contact with human food, i.e., fish etc., antibacterial issues should be considered. All the major parameters of the FSW process, including axial force, rotational speed, and traverse speed as well as tool diameter and tool hardness, were considered to investigate their correspondence effects on the tensile strength and hardness of welded zone. The most important achievement of this research showed that by using SAE for pre-training of neural networks, higher accuracy can be obtained in predicting responses. Finally, the optimal values for various welding parameters were reported as rotational speed: 1600 rpm, traverse speed: 65 mm/min, axial force: 8 KN, shoulder and pin diameters: 15.5 and 5.75 mm, and tool hardness: 50 HRC.

Comparison of microstructural, texture and mechanical properties of SiC and Zn particle reinforced FSW 6061-T6 aluminium alloy

This work investigates the microstructure, mechanical characteristics, and texture evolution of friction stir welding (FSW) of AA6061-T6 metal matrix composites (MMCs) reinforced with silicon carbide (SiC) and zinc (Zn) particles. The SZ region of the SiC and Zn particle-reinforced aluminium matrix (Al-matrix) composites has ultra-fine grain refinements of 4.79 and 4.18 μm, respectively, compared to base metal (BM) particle sizes of 44.97 μm. Ultra-fine grain refinement in the SZ zone produces dynamic recrystallization with particulate-driven nucleation, Zenner Hollomon, and homogeneous SiC/Zn particle distribution in the Al-matrix. Recrystallization texture components P {011} <112>, cube {001} <101>, rotating cube (H) {001} <110>, and F {111} <112>, along with primary shear texture components (B/B¯, and C), suggested DRX at the joint interface in the SiC-reinforced Al-matrix composite. However, the Zn-reinforced Al-matrix composite has a high plain strain, recrystallization, and deformation texture components of copper {112} <111>, Brass {011} <211>, cube {001} <101>, Goss {110}, and P 011 <112>, and major shear texture components (B/B¯ and C). SiC and Zn-reinforced Al-matrix composites have 110 ± 4 and 120 ± 5 HV0.2 average microhardness, respectively. Also, SiC and Zn-reinforced Al-matrix composites have 224 and 236 MPa tensile strengths, respectively.

Investigation of phase transition, mechanical properties, and damping behavior of NiTip/6061Al laminar composites

The microstructure, phase composition, phase transition process, mechanical properties, and damping behavior of NiTip/6061Al laminar composites were investigated by introducing a NiTi particle layer with phase transition characteristics into the 6061 aluminum matrix using rolling composite technology. No defects, such as cracks or holes, were found in the NiTi particle layer, and no agglomeration of the NiTi particles was recorded. The interlayer interface between the alloy particle layer and the 6061Al matrix was clear and well-combined, and no new phase formation occurred in the composite. The composites exhibited phase transition characteristics similar to NiTi alloy particles, and the phase transformation temperature of the composites increased gradually with an extended aging time of the NiTi-reinforced particles. Following aging strengthening, the NiTip/6061Al laminar composites demonstrated higher yield strength than the 6061-T6 aluminum alloy, while their tensile strength remained similar. Pre-aging treatment of the NiTi particles had only a minor effect on the mechanical properties of the composites. The damping capacity of the laminar composites surpassed that of the 6061-T6 aluminum alloy due to the synergistic enhancement of phase transition damping from the NiTi particles and interparticle interface damping within the particle layer The internal friction values of the NiTip/6061Al laminar composites at 60 °C and 350 °C were up to 0.0134 and 0.1146, respectively, which were 211% and 313% higher than those of the 6061-T6 aluminum alloy at the corresponding temperature. The storage modulus and the comprehensive damping performance (EIF) of the NiTip/6061Al laminar composites were higher than those of the 6061-T6 aluminum alloy.

Fatigue behavior of notched and unnotched 7075-T6 aluminum alloy subjected to retrogression and re-aging (RRA) heat treatment and plasma nitriding

Aluminum alloys are widely used in aircraft components, which present the fatigue process as one of the main failure modes. The aeronautical industry has been searching for alternatives to increase the service life and safety of structural components. To address this issue, this work subjected the 7075-T6 alloy to retrogression and re-aging (RRA) heat treatment and plasma nitriding in order to obtain an improvement in the corrosion resistance. The objective was then to evaluate whether such treatments affected the fatigue behavior. Fatigue tests were carried out on the material with a smooth surface and with a notch (theoretical stress concentration factor of 5.7). A maximum likelihood estimation method was used to estimate the S-N curve parameters. The fatigue behavior without notch for the T6 and RRA treatments was similar, which is expected because the resulting microstructure of the RRA condition is composed of a homogeneous distribution of very fine η’ precipitates in the aluminum matrix, similar to the T6 condition. The worst fatigue behavior without notch was found for the material underplasma nitriding for two main reasons: the softening of the microstructure after processing and the substantial increase of the surface roughness. Regarding the notched material, the fatigue performance was reduced to a similar level regardless of the condition.

Study of vibration frequency-fatigue strength action of 6061-T6 aluminum alloy during fillet welding

The research mainly focuses on the fatigue strength characteristics of 6061-T6 aluminum alloy fillet welds under different vibration frequencies. Firstly, by introducing Stress Life Curve (S-N Curve) and Probability Stress Life Curve (P-S-N Curve), the external vibration stress effects of the main load-bearing points in the stress environment of welded joints are analyzed. Subsequently, a vibration test control system is designed to analyze the relationship between vibration frequency and fatigue strength through nominal stress analysis and hot spot stress analysis. The research findings revealed that under the nominal stress analysis method, the P-S-N fitting curve showed a declining trend with an increase in fatigue life for stress variation curves with survival rates of 50 %, 95 %, and 97.7 % at vibration frequencies of 57.5 Hz, 67.5 Hz, and 77.5 Hz. At the same survival rate stress conditions, the fatigue life variation formed by resonance frequency was smaller, and the fatigue life in the resonance state was relatively lower. There is a certain correlation between vibration frequency and fatigue strength, with resonance frequency corresponding to relatively low fatigue life. This research result helps to reveal the fatigue behavior of 6061-T6 aluminum alloy fillet welds under different vibration stresses, providing a reference for the structural safety design of aluminum alloy components.

Mechanical Properties of Nano SiC Reinforced Aluminum 7075-T6 Produced by Warm Powder Compaction using an Inert Gas

The micron-sized Al7075powder reinforced with nano-sized SiC particles is compacted at 4000C in an inert atmosphere using Nitrogen. It is shown that this technique can significantly improve the mechanical properties of the compacted powder characterized by measuring hardness, stress-strain curves and density. The maximum relative density was %98.8 and obtained for 2.3 GPa pressure and 0%SiC content. The minimum density was %93.95 and was obtained for 10%SiC content and 1.3 GPa pressure. The degree of porosity and the number and size of the void decreased as the compaction pressure increased and increased with the increase of SiC volume fraction. The maximum increase in ultimate strength was about 72% and occurred for the 5%SiC content and the 1.3 GPa compaction pressure. For 10%SiC volume fraction the strength improved by 53% for 2.6 GPa pressure. The effect of SiC content on ultimate strength was significantly higher than that of the compaction pressure. The maximum increase in Vickers hardness of the compacts was 100% and obtained for the samples with 10%SiC volume fraction and compacted at 2.6 GPa pressure. Again, the effect of SiC volume fraction on hardness improvement was found to be remarkably greater than that of compaction pressure.

Preparation of 2024-T351 aluminum alloy superhydrophobic surface by laser peening without absorption layer and without confinement layer

The purpose of this study was to investigate the preparation of superhydrophobic surfaces on 2024-T351 aluminum alloy by laser peening without absorption layer and without confinement layer (LPwAC). The wettability, residual stress and microhardness of the treated specimens were measured. The surface morphology of the specimen was characterized by scanning electron microscopy, and the surface elements and crystal orientation were analyzed. The experimental results showed that the micro-nanoporous structure appeared on specimen surface after LPwAC treatment. The superhydrophobic state was observed after chemical modification reduced the surface energy. Additionally, the crystallinity of the surface was increased, the hardness was improved, and residual compressive stress was generated inside the material. LPwAC is an effective process for the preparation of stable 2024-T351 aluminum alloy superhydrophobic surfaces.

Design and analysis of longitudinal–flexural hybrid transducer for ultrasonic peen forming

Ultrasonic peen forming (UPF) is an emerging technology that exhibits great superiority in both its flexible operating modes and the deep residual stress that it produces compared with conventional plastic forming methods. Although ultrasonic transducers with longitudinal vibration have been widely studied, they have seldom been incorporated into UPF devices for machining in confined spaces. To meet the requirements of this type of machining, a sandwich-type piezoelectric transducer with coupled longitudinal–flexural vibrational modes is proposed. The basic structure of the transducer is designed to obtain large vibrational amplitudes in both modes. Experimental results obtained with a prototype device demonstrate the feasibility of the proposed transducer. The measured vibrational amplitude for the working face in the longitudinal vibrational mode is 1.0 μm, and electrical matching increases this amplitude by 40%. The flexural vibration characteristics of the same prototype transducer are also tested and are found to be slightly smaller than those of longitudinal mode. The resultant working strokes of the UPF impact pins reach 1.7 mm and 1.2 mm in the longitudinal and flexural modes, respectively. The forming capability of the prototype has been evaluated via 15-min machining on standard 2024-T351 aluminum plates. After UPF, an improved surface morphology with lower surface roughness is obtained. The aluminum plate test piece has an apparent upper deformation with an arc height of 0.64 mm. The measured peak value of the compressive residual stress is around 250 MPa, appearing at a depth of 100 μm. The proposed longitudinal–flexural hybrid transducer thus provides a high-performance tool for plate peen forming in confined spaces.

Ultimate behaviour of aluminium alloy I-beams: New experimental tests and European codification

In this work, the ultimate behaviour of I-shaped aluminium beams and a comparison with the current design provisions reported in the Eurocodes are presented. A total number of 15 three-point bending tests are carried out on extruded beams made of 6060-T66, 6082-T6 and 6005A-T6 aluminium alloys at the Strength laboratory of the University of Salerno. The tested cross-sections are characterized by different width-to-thickness ratios and, three different lengths are considered: 1300 mm, 800 mm and 500 mm. Material properties, maximum flexural resistance, rotation capacity and failure mode were fully reported within this manuscript. Moreover, a total number of 86 experimental tests are collected from the scientific literature and, a comparison between the experimental results and those obtained by current design provision EN 1999−1−1 is provided. In the case of bending moment, the experimental results are used to evaluate the accuracy of the new methodologies currently proposed in the Annex L of the new Eurocode 9 draft, i.e. the extension of effective thickness method. The EN 1999 proposal showed a higher accuracy in estimating the I-shaped flexural resistances.

Fatigue life estimation of aircraft structural component using FE approach and validation through analytical and experimental methods

Aircraft structural design requirements encompass safe-life and damage-tolerant design, analysis, and verification through testing to arrive at the overall service life. The fatigue phenomenon is most critical and local; hence fatigue studies are necessary to conduct first at the coupon level before attempting at the component or full-scale level. The present work demonstrates the development of fatigue life estimation procedures such as high cycle fatigue (HCF) life and fatigue crack growth (FCG) life on specimens as per ASTM standards.The HCF life is predicted for the Aluminum (Al) 2024-T3 ASTM E466 specimen subjected to constant amplitude loading with a stress ratio (R) of 0.1 based on Basquin's method. The computational 2D finite element (FE) model is developed to predict HCF life using a safe-life approach through Nastran Embedded Fatigue (NEF). The effect of fatigue strength modifying factors affecting fatigue life is also explored. Similarly, the FCG life is predicted for the Al 2024-T3 ASTM E647 specimen subjected to constant amplitude loading with a stress ratio of 0.1 using Walker's equation. The computational 3D FE models with a single edge crack in each are developed to predict FCG life using FRANC3D. The FE-based HCF and FCG life prediction procedures demonstrated in this work are verified by comparing FE results with analytical and experimental ones. Therefore, these FE-based methodologies for HCF and FCG life prediction can be adopted at the feature and structural component levels. The developed computational methods reduce the experimental effort, cost, and time involved in the overall fatigue design of the aircraft structures.

Varying rotational speeds and their effect on the mechanical properties of friction stir welded 6082-T651 aluminium alloy plates

The need to understand the effects of varying rotational speeds on the mechanical properties of Friction Stir Welded 6082-T6 aluminium alloy plates motivated this study. The rotational speeds used were influenced by the capabilities of the Friction Stir Welding machine used. The lowest rotational speed used on the machine was 680 rpm followed by 780 rpm and 900 rpm respectively. The rotational speed is the rate at which the welding tool rotates around its axis and is one of the most important parameters in Friction Stir Welding. Speeds are related to processing temperature which influences the underlying physical conditions of the material. The changes in rotational speeds had an influence on the resulting mechanical properties. The change in rotational speed affected heat distribution in the weld area causing changes in the ductility of the Heat Affected Zone (HAZ) which affected weld behavior during mechanical testing and how these failed during testing. The optimal welding rotational speed was obtained during the welding of 6082-T6 aluminium alloy plates used in this study. This observation is also backed by mechanical evaluation done on friction stir welded plates used and results compares to work of other researchers in the field. In terms of hardness, in the weld area, the optimum speed had a higher average hardness distribution in the weld area. Heat distribution in the weld area caused changes in the ductility of the Heat Affected Zone (HAZ) and this was proven during tensile testing. Vickers hardness across the weld area revealed changes in the hardness of the base metal and the weld area. Changes in tensile strength due to changes in rotational speed are also documented and reported on. The plunge depth, tilt angle and welding speed were kept constant throughout the duration of the welding procedure. This made it easier to analyze and compare the resulting changes in the properties of Friction Stir Welded 6082-T651 aluminum alloy plates.

Effect of post-welding coating process on the organization and properties of MIG-welded T-joints of 6063-T6 aluminum alloy

Abstract With the rapid development of the precision industry, aluminum alloy structural parts have been widely used. However, in the welding process of aluminum alloy, there are problems such as welding deformation and weld tumor defects due to the special physical characteristics of aluminum alloy. Therefore, this paper mainly focuses on 6063-T6 aluminum alloy as the research object to analyze the effect of the coating process on the organizational properties of MIG welded T-joints of 6063-T6 aluminum alloy. First, based on the Simufact welding finite element analysis platform, the establishment of a three-dimensional welding simulation model, the simulation calculations and test results for comparison, the peak temperature and temperature change trend of each measurement point between the two. Secondly, according to the T-joint welding process, welding numerical simulation of 6063-T6 aluminum alloy rear compartment structural parts to obtain the rear compartment assembly welding residual stress is mainly concentrated in the vicinity of the weld. Finally, the impact of welding current on the organization and properties of T-shaped welded joints of 6063-T6 aluminum alloy was discussed. The results show that the coating process has a good strengthening effect on the mechanical properties of welded joints. Compared with the pre-coating process, the welded joint tensile strength increased by 14.93%, and the welding coefficient of 73% of the parent material heat-affected zone microhardness increased by 21.82% compared to the pre-coating process. In this paper, the finite element theory of the coating process and MIG welding, T-joint organization between the found welding heat-affected zone after the coating process can make Mg, and Si atoms continue to be enriched, and mechanical properties strength is enhanced.

Effect of Web Perforations on the Web Buckling Resistance of 7075-T6 and AA-6086 High-Strength Aluminium Alloy C-Shaped Members under End-Two-Flange Loading Case

Recently, new types of C-shaped members made from AA-6086 and 7075-T6 high-strength aluminium alloy have become more popular due to their high yield strength and lower cost. These members are often manufactured with pre-punched web perforations to simplify the installation of services, but this can reduce their strength. Also, such aluminium C-shaped members that contain perforated webs are vulnerable to web buckling failure, as aluminium alloy has a lower elastic modulus compared to steel. However, this influence has not been investigated for high-strength aluminium alloy sections to date. An extensive numerical investigation was undertaken to examine the effect of web perforations on the web buckling resistance of high-strength aluminium alloy C-shaped members under an end-two-flange (ETF) loading case, and this study focused on two types of aluminium alloys, namely 7075-T6 and AA-6086. To achieve this, a nonlinear finite element (FE) model was developed and validated using the test data in the literature. The material properties used in the FE models were obtained from the relevant literature. A parametric investigation was carried out, consisting of a total of 1458 models. In this investigation, a number of variables were examined, including the web hole size, web hole location, bearing length, fillet radius and aluminium alloy grades. The results showed that increasing the a/h ratio from 0.1 to 0.5 resulted in a decrease of 9.7% and 9.3% in the web buckling resistance for the 7075-T6 aluminium and AA-6086 aluminium, respectively. When the length of the bearing plates (N) varied from 100 mm to 200 mm, the web buckling resistance experienced an average increase of 61.7% for the 7075-T6 aluminium and 54.1% for the AA-6086 aluminium. Also, the web buckling resistance increased by 6.2% for the 7075-T6 aluminium alloy, while the strength increased by 4.0% for the AA-6086 aluminium alloy when the x/h ratio increased from 0.1 to 0.5. The numerical data generated from the parametric study were used to assess the accuracy and suitability of the latest design recommendations, and it was found that the design rules presented in the previous literature cannot provide reliable and safe predictions for estimating the web buckling resistance of aluminium C-shaped members that contain perforated webs under an ETF loading case. Finally, new design formulas were proposed in the form of strength reduction factors. A reliability assessment was then undertaken, and the results of this analysis indicated that the proposed design formulas can accurately predict the web buckling resistance of such members with perforated webs.

Simultaneously increased strength and plasticity of TIG-welded 7075-T6 aluminum alloy joints via a novel post-weld composite treatment process

The 7075-T6 aluminum (Al) alloy is a high-strength material with great application potential. However, the tensile strength and elongation of its arc-welded joints are severely reduced compared to the base metal (BM), with only 57.3% and 14.4% of the BM values, respectively. To improve both strength and plasticity simultaneously, a novel post-weld composite treatment process combining solution treatment, partial rolling, and natural aging treatment (SRA) was proposed. The SRA process enhanced the strength and elongation of welded joints to 84.5% and 83.1% of the BM, respectively. In different regions of the joints, the SRA process involved different strengthening mechanisms, including stronger work hardening in Region I, η′ phase precipitation and weaker work hardening in Region II, and refinement of the η’ and η phase in Region III. The SRA process also improved the formability of the welded joints from 62.5% to 87.5% of the BM. In addition, the SRA process increased the median fatigue life of welded joints by a factor of approximately 2–6. This was achieved by increasing the strength and microhardness of the fusion zone, which, in turn, reduced the number of fatigue crack sources and shifted crack sources from the surface to subsurface regions.

Effect of Patch Interface Strengthening on Mechanical Properties of Epoxy/Carbon Fiber Sheet by Double-Sided Patching

To repair the damage to the epoxy/carbon fiber laminate, a single-lap test was performed between sulfuric acid anodized aluminum plate and carbon fiber laminate to study the effect of the anodized layer on the interlaminar shear strength. Then, carbon fiber laminates were prepared by wet-laying method to simulate the damage caused by penetrating cracks, and double-sided adhesive sheets were made from 0.5[Formula: see text]mm thick 2024-T3 aluminum alloy and carbon fiber laminates to match the thickness and material of the simulated damage plate. The adhesive matrix used was E51 bisphenol-A epoxy resin with 1.5[Formula: see text]wt.% nanorubber added for modification and toughening. After double-sided patching, tensile tests were performed to investigate the effect of different materials on the tensile strength of double-sided adhesive patches. We observed SEM images of the fracture surface of the patch after tensile failure and analyzed the strengthening mechanisms of different material patches. The results show that the shear strength between the single-layer sulfuric acid anodized aluminum plate and the carbon fiber laminate is 9.792 MPa, which is 61.5% higher than the shear strength of the nonanodized aluminum plate. The tensile strength of the 2024-T3 aluminum patch specimen is 271.83 MPa, which is 48.43% and 23.97% higher than the perforated specimen without patch and the specimen with carbon fiber laminate patch, respectively, and reaches 72.56% of the undamaged carbon fiber laminate. The specimens with aluminum plate patches showed a maximum bending strength of 616.47 MPa, which increased by 70.83% compared to the 360.875 MPa of the perforated specimens. The maximum bending strength of the aluminum plate patch specimen reached 74.76% of that of the undamaged specimen. However, the maximum bending strength of the composite patch specimen is as high as 1101.9 MPa, far exceeding that of other samples. Due to the poor toughness of the sample, it cannot withstand large strains. The addition of 1.5[Formula: see text]wt.% nanorubber results in shear yield bands and induces silver grains to absorb a large amount of energy during stress deformation.

Mechanical Properties of 6061 Aluminum Alloy under Cyclic Tensile Loading

During the service process of an aluminum alloy structure, its complex deformation zone experiences repeated loading problems such as repeated tension, compression, bending and reverse bending. At the same time, the cyclic loading and heat treatment process also have a certain impact on the mechanical properties of aluminum alloy extruded tubes. Therefore, the study of heat treatment process parameters has important engineering and practical value for the mechanical properties of aluminum alloy extrusion tubes under cyclic loading conditions. The experiment takes 6061-T6 aluminum alloy extruded tubes as the research objects. In the study, heat treatment and cyclic tensile tests were carried out on 26 aluminum alloy specimens to study the effects of different heat treatment parameters (such as heating temperature, holding time, and cooling method) on the stress–strain hysteresis curves, stress characteristics, hysteretic energy, skeleton curves and failure characteristics of the alloy under the same loading system. In addition, different cyclic tensile tests were carried out on 20 aluminum alloy samples without secondary heat treatment to discuss the effects of different cyclic loading regimes on the mechanical properties of the alloy. The research results indicate that the effect of heating temperature on the cyclic loading performance of the alloy is greater than that of the holding time, and the effect of the cooling method on the cyclic loading performance of the alloy is not obvious. A cyclic tensile loading regime has a significant impact on the strength, elongation and hysteresis energy of the alloy. The hysteretic behavior of the alloy during cyclic tensile loading depends on the applied stress level and loading history. As the number of cycles increases, the shape of the hysteresis curve tends to be stable, but there is no monotonic relationship between the number of cycles loaded and the hysteresis energy.

Enhancement of saltwater ageing behavior of nanocomposites and lap joints with boron nanoparticles

The presented research aims to enhance the ageing performance of nanocomposites and bonded joints in the saltwater medium with boron nanoparticle doping. Epoxy nanocomposites and bonded aluminum 2024-T3 joints doped with 2 wt% silane-functionalized boron carbide (B4C) and boron nitride (BN) nanoparticles and undoped were produced for that purpose. The produced samples were immersed in a saltwater (10% NaCl) solution at 40 °C for 480, 960 and 1440 h. By performing the weight change test, Fourier transform infrared (FT-IR) spectroscopy, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), tensile test and scanning electron microscope (SEM), the research aimed to comprehensively assess the changes in the properties of nanocomposites and lap joints after exposure to saltwater ageing, shedding light on the effectiveness of boron nanoparticle doping in improving their performance in saltwater environments. The result showed that thanks to the anti-plasticisation behaviour of nanoparticles, 18.4% and 19.6% higher Tg values were obtained in B4C and BN-doped nanocomposites after 1440 h of ageing, respectively. Similarly, the static tensile strength of the undoped composite decreased by 22%, while B4C and BN-doped nanocomposites decreased by 15% and 14%, respectively, at the end of ageing. After 1440 h, the storage modulus of undoped, B4C and BN-doped nanocomposites decreased by 24.2%, 15.3% and 11.9%, respectively. It was found that B4C and BN-doped bonded joints performed superior mechanical properties compared to their undoped counterparts. The joints doped with B4C and BN nanoparticles carried 50% and 52% higher loads than the undoped joint.

Determining the Elastic Constants of Isotropic Materials by Measuring the Phase Velocities of the A0 and S0 Modes of Lamb Waves.

In this study, a new method for determining the elastic constants of isotropic plates using Lamb wave fundamental modes is presented. This method solves the inverse problem, where the elastic constants (Young's modulus and Poisson's ratio) of the plate were estimated by measuring the phase velocities of the Lamb wave using the Rayleigh-Lamb equations to find the solution and determining the phase velocities of the A0 and S0 modes using a new method. The suitability of the proposed method for determining the elastic constants was evaluated using simulated and experimental signals propagating on an aluminum plate. The theoretical modeling on the aluminum 7075-T6 plate shows that the proposed method allows the determination of the Poisson ratio with a relative error not exceeding 2% and Young's modulus with a relative error not exceeding 0.5%. The experimental measurements of an aluminum plate of known thickness (2 mm) and density (2685 kg/m3) confirmed the suitability of the proposed method for the measurements of elastic constants. In the proposed method, the processing of ultrasonic signals can be performed in real-time, and the values of the elastic constants can be obtained immediately after scanning the required distance.

Ultrasonic spot-welding of AA 6061-T6 aluminium alloy: Optimization of process parameters, microstructural characteristics and mechanical properties of spot joints

The ultrasonic spot welding (USW) is used to develop the lap joints of AA 6061-T6 aluminium alloy because it is difficult to spot weld using resistance spot welding (RSW) and laser beam spot welding (LBSW) processes due to its high electrical conductivity, thermal conductivity and light reflectivity respectively. The main objective of this investigation is to optimize the USW parameters specifically welding time (s), amplitude (%) and pressure (bar) for enhancing the tensile shear fracture load (TSFL) bearing capability of AA 6061-T6 aluminium alloy lap joints for automotive applications. The statistical response surface methodology (RSM) was utilized for generating strength prediction models (SPM) and validated using analysis of variance (ANOVA). The RSM is widely used for optimizing the process parameters as it provides greater information such as optimum conditions, direct effect of process parameters and performance prediction from limited number of experiments compared to other optimization techniques. The response surfaces were created using RSM and analyzed. The effect of USW parameters on macrostructure, microstructure and TSFL of USW joints was studied. From the results, it was observed that the USW joints created using the welding amplitude of 100%, welding time of 21 s and welding pressure of 6 bar exhibited greater TSFL capacity of 5.08 kN. The SPM accurately predicted the TSFL of USW joints within 5% error on 95% confidence. Welding pressure disclosed major effect on TSFL of USW joints followed by welding amplitude and time. The greater TSFL of USW joints is imputed to the better coalescence of weld surfaces and refined microstructure.

Effect of natural aging on the tensile properties and the toughness of friction stir welds of 2024-T3 aluminum alloy

During friction stir welding of metallic alloys, four different microstructure zones are formed in the weld, resulting in heterogeneous mechanical properties in this latter. In the case of aluminum alloys, these properties are bound to change with aging, whether natural or artificial. In this study, changes in the toughness and tensile behavior of friction stir welds in Al 2024-T3 alloy over time are investigated. Only specimens found to be defect free, by X-ray imaging, are tested. Characterized by the area under the stress-strain curve of the material, the toughness is found to be 19% lower after 24 months of natural aging. This decrease in toughness is mainly due to a loss of ductility as the elongation of the material drops by 27% while the ultimate tensile strength increases by 9%. The fracture zone and pattern remain the same for both natural aged and freshly welded specimens. These results can be used to estimate the service life of structures using such a material, as in aeronautics.