Search Results (165)

This paper describes the development of a new hybrid composite for the metal joints of aluminium and glass fibre composite adherents. The aluminium adherend is manufactured using friction stir-formed studs that are inserted into the composite adherend in the through-thickness direction during the composite manufacturing process, where the dry fibres are displaced to accommodate the studs before the resin infusion process. The materials used were AA6082-T6 aluminium and plain-woven E-glass fabric reinforced epoxy, with primary applications in naval vessels. This joining approach offers a cost-effective solution that does not require complicated onsite welding. The joint design was developed based on a simulation test program with finite element analysis, followed by experimental characterisation and validation. The design solution was analysed in terms of the force displacement response, sequence of load transfer, and characterisation of the joint failure modes. Full article

Variations in the warm formability of AA7075 sheets are primarily attributed to differences in precipitate morphology resulting from distinct thermal histories. To better understand this relationship, this study systematically investigates the influence of precipitate characteristics—quantified by the product of precipitate volume fraction and average radius—on forming limits across various thermal routes in warm forming processes. A modified Cockcroft–Latham ductile fracture model incorporating this microstructural parameter was developed, calibrated against experimental data from warm isothermal Nakajima tests, and implemented within a finite element framework. The proposed model enables the accurate prediction of forming limit curves with minimal experimental effort, thereby significantly reducing the reliance on extensive mechanical testing. Building upon the validated FE model, a practical methodology for rapid R-value estimation under warm forming conditions was established, involving the design of specimen geometries optimised for isothermal Nakajima testing. This approach achieved R-value predictions within 5% deviation from conventional uniaxial tensile test results. Furthermore, experimental results indicated that AA7075 sheets exhibited nearly isotropic deformation behaviour under retrogression warm forming conditions. Overall, the methodology proposed in this study bridges the gap between formability prediction and process simulation, offering a robust and scalable framework for the industrial optimisation of warm forming processes for high-strength aluminium alloys. Full article

Aluminium alloy (AA) bars have emerged in structural engineering applications mainly to reduce deterioration caused by corrosion. However, research on AA-reinforced concrete (RC) beams has been limited, despite RC beams reinforced with AA bars providing a study area with great potential. Therefore, this study mainly aims to investigate the behaviour of AA RC deep beams. The investigated parameters include concrete strength, tension reinforcement ratio, beam size, a/d ratio, and transverse reinforcement ratio, most of which have not yet been thoroughly studied. A finite element (FE) model was developed to obtain accurate predictions. The developed FE model predicted the actual load-bearing capacity with a mean value of 1.00. The findings indicated a clear trend in which shear force capacity increased from 124.1 to 181.4 kN with increasing concrete compressive strength from 20 to 40 MPa. A strong relationship between the reinforcement ratio and failure mode was obtained. The shear strength decreased from 2.95 to 2.1 MPa as the effective depth increased from 175 to 350 mm. An increase in transverse reinforcement ratio instigated an enhancement in shear force capacity. Finally, the applicability of the design models in the current literature was evaluated. The design formulations gave accurate predictions with an error of 3%. Full article

In the present article, the effect of artificial ageing on tensile mechanical properties and resistance to corrosion of aluminium alloy 2198-T3 was investigated. The results were obtained under the framework of the Greek National project “CorLi”, which was targeted to document the mechanical behaviour of the alloy under different artificial ageing conditions, simulating the natural ageing of aircraft structures during their operation lifespan. Four (4) different ageing conditions corresponding to under-aged (UA), peak-aged (PA), and over-aged (OA) tempers based on the initial, T3 temper, were considered. In the PA condition, the conventional yield stress R_p0.2% increased by more than 50% with a simultaneous 46% decrease in tensile elongation at fracture A_f. Additionally, the effect of corrosion was found to be different for the different artificial ageing tempers of AA2198, with lower charge transfer resistance (R_CT) observed for artificially aged specimens. Nevertheless, the corrosion-induced degradation rate of R_CT was found to decrease with increasing ageing time. Full article

The coil current frequency and waveform have a great impact on the forming performance of the workpiece in electromagnetic forming. However, existing research is mostly limited to analyzing the influence of either frequency or waveform on the forming outcome independently, which makes it challenging to fully reveal the intrinsic relationship between current parameters and forming results. In this work, three discharge circuit structures are developed to generate different coil currents composed of various frequencies and waveforms, and their effects on deformation of AA6061 Aluminium alloy tube are systematically investigated through numerical and experimental approaches. Results show that a conventional circuit can generate an attenuated oscillating sinusoidal waveform consisting of several pulse half-waves, while a circuit composed of a thyristor switch can generate a half-wave current, and a circuit consisting of a crowbar circuit can generate a current with a slow decay rate. Further, it is found that at a high-frequency discharge, a current having a slow decay rate is favorable for forming efficiency, as well as reducing coil temperature, while at a low-frequency discharge, the current waveform has almost no effect on the forming efficiency; thus, a half-wave current is highly recommended to significantly reduce the coil temperature. The obtained results are of great significance in guiding the design of coil currents and optimizing electromagnetic forming technology. Full article

Recently, rotary friction welding has been used to join magnesium alloys. FRW uses friction heat to bond magnesium alloys with aluminium alloys. Combining these light alloys can provide many promising applications in the industry. The welding parameters such as friction and upsetting force, rotational speed, and welding time play a significant role in determining the joint strength. The paper presents a new approach to multi-objective optimisation of friction welding process parameters for AZ91D/AA6082 alloy joints. Multi-objective optimisation is based on artificial neural networks and genetic algorithms as non-conventional AI techniques. The methods were used to determine the following optimal welding process parameters: friction force, upsetting force and friction time for simultaneously maximised tensile strength and minimised metal loss (shortening) during welding. The ultimate tensile strength and metal loss of the friction welding joints were studied numerically and experimentally. Moreover, the influence of welding parameters on the ultimate tensile strength and shortening of friction joints was also studied. A genetic algorithm successfully found a set of welding parameters for which the joint strength increases from 24 to 81 MPA and the joint shortening decreases from 8.25 to 0.23 mm. The results show that a low friction force and upsetting force give a high value of tensile strength and the lowest shortening of the bimetal joints. Full article

The use of computer simulation to imitate physical processes has proven to be a time-efficient and cost-effective way of performing scenario testing for process optimisation in different applications. The finite element analysis (FEA) is the dominant numerical simulation method for analysing sheet metal forming processes. It uses mathematical tools and computer-aided engineering software programmes to predict forming processes. To improve the quality of output from the simulation, accurate material characterisation data that correctly model the behaviour of the material when it undergoes deformation must be provided. This paper outlines the stages of conducting material characterisation experiments, such as tensile, hardness, and formability tests, using the aluminium alloy AA1050-O. Sample preparation, the machine setup, and testing procedures for the material characterisation tests are given. Subsequent data preparation methods for input into an FEA software programme are also outlined. Implications of the testing results to a deep drawing process are examined while considering the formation of a rectangular monolithic component measuring 2300 mm by 1400 mm with a drawing depth of approximately 150 mm. The results from the characterisation tests indicate that the forming process for the product can be achieved using cold forming at room temperatures as a 25% strain was recorded before necking against an anticipated uniaxial strain of 5.93%. The aluminium alloy AA1050-O demonstrated a negligible strain rate sensitivity in the forming region, thus eliminating tool velocity from the key process parameters that should be considered during FEA simulations. A 50% increase in hardness was recorded after strain hardening. Full article

The study aimed to develop a superhydrophobic coating on the aluminium alloy 2024-T3 surface. The desired surface roughness and low surface energy were achieved with SiO₂ nanoparticles, synthesised via the Stöber method and modified with alkyl silane (AS) or perfluoroalkyl silane (FAS). To enhance particle adhesion to the alloy substrate, nanoparticles were incorporated into a hybrid sol–gel coating composed of tetraethyl orthosilicate, methyl methacrylate, and 3-methacryloxypropyl trimethoxysilane. The coated substrates were characterised using field emission scanning and transmission electron microscopy with energy-dispersive spectroscopy for surface topography, nanoparticle size distribution, composition, and coating thickness. The corrosion resistance of the coatings on AA2024-T3 was evaluated in a 0.1 M NaCl solution using electrochemical impedance spectroscopy. The synthesised SiO₂ nanoparticles had an average size between 25 and 35 nm. The water contact angles on coated aluminium surfaces reached 135° for SiO₂ + AS and 151° for SiO₂ + FAS. SiO₂ + FAS, indicating superhydrophobic properties, showed the most uniform surface with the most consistent size distribution of the SiO₂ nanoparticles. Incorporation of nanoparticles into the hybrid sol–gel coating further improved particle adhesion. The ~2 µm-thick coating also demonstrated efficient barrier properties, significantly enhancing corrosion resistance for over two months under the test conditions. Full article

Polybenzoxazine (PBz) resins exhibit excellent mechanical, thermal, and adhesive properties, making them interesting candidates for coating applications. Moreover, thanks to the incorporation of exchangeable ester bonds within the PBz network, the coating presents healable properties that are catalyzed by the intrinsic presence of tertiary amine within the PBz backbone. Unfortunately, these tertiary amine functions are also responsible for the limited resistance of such systems to acid environments by protonation. To address this limitation, the protection of tertiary amines inherent to the PBz network was investigated in this study by incorporating an aromatic group close to the amine function to minimize its protonation via hindrance/mesomeric effects. More precisely, benzoxazine precursors based on monoethanolamine (mea) and aminophenylethyl alcohol (Apa) were synthesized and tested as protective coatings of aluminium alloy substrates (AA1050). The resins were characterized by NMR, FTIR, rheology, TGA, DSC, and DMA. PBz synthesized from Apa exhibits enhanced thermal stability, reduced swelling rates in both water and acid, and shortened relaxation times. After application via solvent casting on AA1050 substrates, the acid resistance of the coatings was evaluated. Electrochemical impedance spectroscopy results demonstrated better resistance of the Apa-based resins in 0.1 M sulfuric acid after one month of immersion. Full article

Aluminium metal matrix composites (AMMCs) using alumina (Al₂O₃) and silicon carbide (SiC) as reinforcement elements are gaining significant interest in various applications because of their excellent properties. In this study, Al₂O₃/SiC with compositions (0.5 wt.%, 1.5 wt.%, and 2.5 wt.% for each) were used as reinforcement elements in an aluminium alloy (AA2024-T6). The samples prepared were AA2024-T6 + (0.5Al₂O₃/0.5SiC), AA2024-T6 + (1.5Al₂O₃/1.5SiC), and AA2024-T6 + (2.5Al₂O₃/2.5SiC) using a stir-casting technique. The experimental study included density calculation mechanical properties, such as tensile strength, compressive strength and hardness. The study also included a microstructure examination of the fracture surface of the tensile specimens. The results showed that incorporating Al₂O₃/SiC as reinforcement materials into aluminium AA2024-T6 significantly improved its properties. Hence, increasing the reinforcement with compositions of 2.5Al₂O₃/2.5SiC into AA2024-T6 showed a drop in density and increased mechanical properties, such as ultimate tensile strength, compressive strength and hardness, compared to the base alloy (AA2024-T6). Furthermore, the scanning electron microscopy analysis revealed the uniform distribution of the reinforcement particles resulting in strong bonding with the matrix. The findings suggest that Al₂O₃/SiC reinforced with AA2024-T6 can be used in applications where a combination of lightweight and high strength is needed. Full article

This study aims to explore the effects of various pre- and post-weld heat treatments (PWHTs) on the microstructural and mechanical properties of dissimilar aluminium alloys, namely AA7075 and AA2024, joined through rotary friction welding. The joints were rigorously evaluated through multiple characterization methods, revealing no signs of cracking or incomplete bonding. This study observed that dissimilar joints between AA7075 and AA2024 alloys showed increased flash formation on the AA7075 side due to its lower melting point relative to the AA2024 alloy. Various zones within the weld region were identified, such as the dynamic recrystallized zone (DRZ), the thermo-mechanically affected zone (TMAZ)—which includes TMAZ-1 with elongated grains and TMAZ-2 with compressed or distorted grains—the heat-affected zone (HAZ), and the base metal (BM) zone. Of all the welding conditions examined, the post-weld heat-treated (PWHT) AA2024/AA7075 joint produced by rotary friction welding showed the highest strength, with a yield strength (YS) of 305 ± 2 MPa and an ultimate tensile strength (UTS) of 477 ± 3 MPa. This improvement in strength can be attributed to the significant strengthening precipitates of MgZn₂ (found on the AA7075 side), θ-Al₂Cu, and S-Al₂CuMg (found on the AA2204 side) formed during post-weld ageing. Notably, all dissimilar welds failed in the HAZ region on the AA2024 side due to coarse grain formation, identifying this as the weakest area. Full article

Aluminium and its composites are widely used in production to enhance the strength of lightweight objects. In this study, an AA7075/SiC composite was fabricated using a stir casting route. Multi-objective optimization and finite element analysis were performed with various process parameters on a manufactured aluminium composite (AA7075 + SiC) undergoing a laser beam welding process. Four welding parameters, i.e., pulse frequency, power, welding speed (transverse), and wire size were taken for laser welding as per the L-9 orthogonal array for experimental study. Tensile strength, deflection, temperature distribution, Rockwell hardness (fusion zone), and Rockwell hardness (heat affected zone) were taken as output parameters after welding. The standard deviation objective weighting–grey relational optimization method optimized the process parameter. ANSYS APDL 23 software was utilized to simulate the entire laser welding method with a cylindrical heat source to predict the temperature distribution in the butt-welded plates. This software uses finite element analysis and gives a deviation of only 5.85% for temperature distribution with experimental results. This study helps to understand the effect of various parameters on the welding strength of the aluminium composite. Full article

Aluminium metal matrix composites are widely used in automotive, aerospace, marine, and structural engineering due to their high strength-to-weight ratio and superior mechanical properties. Optimizing friction stir process parameters is critical to enhancing the performance of these materials. This study investigates the effects of FSP parameters such as rotational speed, tilt angle, and traverse speed, on the mechanical properties of AA5083/Silicon carbide and AA5083/Coal composites. Using a Taguchi L9 design of experiments, signal-to-noise ratio, and analysis of variance, this study identifies the optimal process settings for maximizing ultimate tensile strength, microhardness, and elongation. From the results, the study revealed that for AA5083/Silicon carbide composites, rotational speed was the most significant factor affecting tensile strength, while for AA5083/Coal composites, tilt angle played a more critical role. Rotational speed consistently influenced microhardness and elongation for both materials. The signal-to-noise ratio analysis indicates that optimal FSP parameters vary depending on the reinforcement material used. This study highlights the importance of tailoring FSP settings to specific reinforcements to achieve optimal mechanical properties. These findings contribute to the advancement of friction stir processing techniques for fabricating high-performance aluminium metal matrix composites, particularly for applications in industries requiring strong, lightweight, and corrosion-resistant materials. Full article

The joining of AA6082-T6 and polyamide 6 using pinless friction stir spot welding was investigated in this study. The influence of the clamping frame geometry was studied and the welds produced were characterized based on their morphology and mechanical performance. The morphological analysis was evaluated based on the comparison of the different joining areas and on the presence of defects in the resolidified layer of the polymer. In turn, the mechanical performance of the joints was evaluated by tensile-shear testing. Additionally, the influence of plunge depth parameter was studied for the clamping frame geometry providing the best mechanical performance. While the clamping frame geometry had a greater impact on the size of the joining areas, therefore influencing the micro-mechanical interlocking mechanisms, the plunge depth mainly affected the plunging of the aluminium into the polymeric material, therefore affecting the macro-mechanical interlocking mechanism. The strongest joints, which failed for a load of about 2700 N, were produced with the clamping frame geometry that restricted the welding zone the least, and used the highest plunge depth. Full article

This study investigates the impact of various auxiliary cooling techniques on machinability, energy consumption, carbon emissions, and economic factors in the drilling process of AA7075T6 aluminium alloy using TiO₂ and C-reinforced composites. The study employed various cooling conditions (dry, MQL, CO₂, and hybrid MQL+CO₂), with different cutting speeds and feed rates, to evaluate their effects on drilling characteristics. The findings indicated that the combined MQL and CO₂ cooling notably enhanced the drilling process by reducing cutting forces by 32% and surface roughness by 65% compared to dry cutting. This synergy between lubrication and cooling significantly improves machinability, resulting in higher-quality machining outputs with smoother surfaces and more precise circularity. Energy analysis revealed that the MQL+CO₂ method reduces energy consumption to 64% observed under dry conditions, underscoring its efficiency through better heat dissipation and reduced friction. Furthermore, this method demonstrates a significant reduction in carbon emissions, contributing to environmental sustainability. Economically, although initial costs associated with the implementation of cooling systems are higher, they are offset by reduced tool wear and energy costs, making it a viable solution for sustainable manufacturing practices. Full article