Volume 67, Issue 7

The design parameters of re-entrant honeycomb (RH) unit cells are effective in determining the auxetic structures’ behavior. This study examines the auxetic response of Ti6Al4V lattice structures fabricated using laser powder bed fusion (L-PBF), focusing on cell parameters (re-entrant angle (Ө), inclined strut length (l), and strut thickness (t)). The auxetic behavior of structures was observed numerically with finite element analysis (FEA) carried out by nTop and experimentally with quasi-static compression tests. The results presented that the minimum Poisson’s ratios (PRs) were obtained as −1.48 and −1.10 for simulation and experiments, respectively. As the absolute value of the PR increases, the auxetic behavior becomes more obvious. The absolute value of the PR increased with the increases in Ө and l, while decreased with the increase in t. The findings of this study offer an important contribution to the development of auxetic structures by adjusting the design parameters.

Dissimilar welding between copper and aluminum presents a challenge because Cu–Al intermetallic compounds (IMCs) are easily generated in the weld seams. Due to the low welding heat input, friction stir welding minimizes contact between the two dissimilar metals and enhances joint performance. In the present study, friction stir lap welding between 6,061 alloy and T2 copper was achieved using two distinct sets of welding parameters. The hardness, shear strength, and microstructure of the two welded joints were comparatively investigated and analyzed. It was found that the hardness of the stir zone in Sample 1, characterized with a low heat input parameter, remained below 100 HV, exhibiting minimal variation. In contrast, regions with significantly higher hardness, reaching a maximum value of ∼370 HV, were observed in the stir zone of Sample 2, characterized by high heat input parameters. Moreover, the shear strength of Sample 1 was 25 % higher than that of Sample 2. Both welded samples fractured at the hook-shaped structures of the copper/aluminum interface. Serrated fracture lines were particularly evident in Sample 1, with a lower hardness value in the fracture region compared to Sample 2.

In this study, the effect of laser power, welding speed, linear heat inputs on the mechanical performance of TWIP980 steels joined by oscillating fiber laser welding in butt welding configuration was investigated. Oscillating fiber laser welding were changed: laser power from 1.2 to 1.6 kW, welding speed from 20 to 30 mm s −1 , linear heat input from 40 to 80 J mm −1 . The tensile, hardness and fatigue tests were carried out to determine mechanical performance. A significant improvement in weld penetration, fatigue performance and mechanical properties was detected at linear heat inputs above 53.33 J mm −1 . The best mechanical properties were obtained at 1.6 kW laser power and 25 mm s −1 welding speed. The study reveals that linear heat inputs, laser power, and welding speed have significant effects on mechanical performance and weld geometry. Furthermore, the results demonstrate that oscillating fiber laser welding enables good weldability even at low laser power.

Constant amplitude fatigue testing on 5,083 and 6,061 dissimilar aluminum alloy tungsten inert gas (TIG) welded lap joints was carried out using an MTS material testing machine, and the typical fatigue fractures of specimens were observed, followed by the life prediction. The results of the fatigue tests showed that the specimens shared different fracture forms at high and low stress levels, in addition to the presence of one specimen that fractured at the weld root. Observation on the fractured specimens at the weld root by scanning electron microscope revealed that there were unfused and porosity defects inside the weld, and the stress concentration at the weld root was high, which led to the cracks to sprout here. Combined with the results of finite element stress analyses, the fatigue lives of welded joints were predicted using the notch stress method and the equivalent structural stress method, respectively. The prediction results showed that both methods are effective in predicting the fatigue life, the prediction results errors are within three factors, and the prediction results are all conservative.

The accelerated corrosion test of self-piercing riveted joints was carried out with 0.02 mol L −1 NaHSO 3  + 0.6 mol L −1 NaCl solution as a corrosion medium. The corrosion characteristics were analyzed using corrosion morphology and corrosion rate. The joint’s mechanical properties and corrosion failure behavior were analyzed by tensile test and scanning electron microscope. Results indicated that the static strength of the joint increased first and then decreased, the strength reduction coefficient fluctuated wildly, and the joint’s stability after corrosion was poor. In the non-lap zone, corrosion pits made the surface rough, and they were scattered. In the lap zone, the upper plate had light corrosion with clustered pits, while the corrosion of the lower plate was severe. Delamination occurred on the lower plate at 360 h, and pits grew deeper and larger at 720 and 1,080 h. The mass loss of the specimen increased in a “stepped” manner, and the corrosion rate increased first, then decreased, and then increased, which was consistent with the morphology evolution law. Due to corrosion, the weak link changed during the load transfer process, and the failure mode of the joint changed from Type (I) to Type (III).

Cast iron components made of gray iron that come into contact with liquids under oscillating pressure may suffer damage caused by cavitation erosion. Understanding the mechanisms of initiation and development of their degradation in operating environments is essential for improving the lifespan and durability of the materials used in these engineering components. This study illustrates the cavitation erosion behavior of gray cast iron with lamellar graphite and a pearlitic metallic matrix, providing a detailed analysis of microstructural images of the damaged surface areas. The tests were conducted using an ultrasonic vibratory apparatus, with potable water from the public supply network as the test liquid. Based on cavitation curves, which were compared to those of unalloyed C45 steel that underwent annealing for softening to achieve a hardness similar to that of cast iron, as well as microscopic observations of the cavitated surfaces, a sequence of deterioration models is proposed to explain the cavitation erosion behavior of this material. The implosion of collapsed bubbles on the surface leads to chipping at the centers of graphite clusters, accompanied by their removal and pitting phenomena along the graphite filaments as well as direct pitting of the metallic matrix. As the number of bubble collapses increases, the number of pits also rises, leading to their coalescence and the formation of fatigue microcracks, which expand and cause ductile removal of the metallic matrix material.

This study investigates the tribological properties of as-received and borided Ti–45Nb alloys when paired with a WC-Co ball and examines the wear mechanisms that occur under dry sliding conditions. Pack boriding treatment applied to β type biomedical titanium alloy samples with improved structural and mechanical properties. The wear performance of both unborided and borided alloys, as well as the counterface and wear debris, were analysed using wear track measurements, weight loss techniques, and scanning electron microscopy. Unborided Ti–45Nb alloy underwent severe wear through multiple wear mechanisms, including tribo-chemical reactions, adhesion, and abrasive wear. Formation of a hard, bonded treatment layer on the Ti–45Nb alloy significantly enhanced its wear resistance up to certain load limits. In this case, mild polishing-type wear occurred, characterized by shallow scratches without weight loss. However, when the applied load exceeded the boriding layer’s load-carrying capacity, the surface layer was completely worn out by abrasive wear assisted delamination, and the alloy experienced severe wear resembling that of the unborided sample. Nevertheless, the volumetric wear rate is still 34 % lower than that of the unborided alloy. WC-Co ball was exposed to mild oxidative wear, particle detachment, abrasion, and micro-cracking wear mechanisms when rubbed against the harder boride layer.

This study aims to produce pure titanium with differing porosity levels for use as a load-bearing implant material that can mimic natural bone structure. Ti + x space holder agent (x: 0, 5, 15, and 20 wt.%) samples were prepared via powder metallurgy route, employing a pressure of 300 MPa followed by sintering at 1200 °C for 6 h. Effect of the space holder agent on the pore characteristics, phase constituent, and mechanical performance, including elastic modulus and ultimate compressive strength, were investigated. Microstructural characterizations were conducted, employing an optical microscope, scanning electron microscopy and energy dispersive spectroscopy. The phase structure was characterized by X-ray diffraction. Additionally, the mechanical behaviour of the samples achieved was assessed by uniaxial compression test at room temperature. The results from the current studies revealed that adding space holder agent effectively modified the porosity level and pore characteristics without altering the phase constituent of the samples. As the space holder agent content was increased from 0 to 20 (wt.%), the porosity level of the samples increased from 18 % to 56 %, while the ultimate compressive strength values reduced significantly from 1,236 MPa to 112 MPa.

The aim of this study is to investigate the impact and biaxial tensile-after impact behaviors of inter-ply hybrid carbon-glass/epoxy composites and reference composites. The samples prepared in five different lamination types such as 1C1G, 2C2G, 3C1G, Ref-C and Ref-G. Samples were subjected to low-velocity impact loading and then subjected to biaxial tensile testing. Some of the non-impacted samples were subjected to biaxial tensile testing for comparison with the results of the impacted samples. From the results obtained, the best impact behavior was shown by 2C2G and Ref-G samples at 17.5 J and 22.5 J energy levels while the weakest impact behavior was shown by samples with 3C1G and Ref-C lamination types for all energy levels. The highest biaxial tensile strength values were obtained in Ref-C samples while the lowest ones were obtained in Ref-G samples. For inter-ply hybrid samples, the highest biaxial tensile strength was obtained for 3C1G samples while the lowest one was determined for 1C1G samples. In addition, it was observed that the biaxial tensile strengths decreased as the energy level value increased for each lamination type. As a result, carbon-glass/epoxy hybridization has shown to have a significant/positive effect on the biaxial tensile strength of composites.

This study aims to explore the potential of quartz, a naturally abundant mineral, as a reinforcing material in the fabrication of metal matrix composites. Al6061 alloy was selected as the matrix material due to its widespread application in the automotive industry. Silicon carbide (SiC), a commonly employed reinforcement in composite manufacturing, was incorporated as a secondary reinforcement in the production of hybrid composites, enabling an investigation into its compatibility with quartz. The composites were fabricated via the powder metallurgy (P/M) technique. Microstructural analysis demonstrated the integration of quartz within the internal structure, revealing a nearly homogeneous distribution of reinforcements with minimal agglomeration. Micro Vickers hardness testing revealed that introducing 10 % quartz enhanced the hardness of the Al6061 alloy by 79.69 %. The most pronounced hardness improvement, however, was achieved in the hybrid composite reinforced with 5 % SiC and 7 % quartz, exhibiting a 108.95 % increase. Wear resistance generally improved by up to 10 % as the reinforcement fraction increased. Notably, the composite reinforced with 5 % SiC and 7 % quartz exhibited the greatest enhancement in wear resistance, surpassing the unreinforced alloy by 369.23 %. Furthermore, the thermal conductivity (TC) coefficient of the composite reinforced with 7 % quartz decreased by 7.54 % relative to the unreinforced alloy.

Carbon fiber laminates can be made of different materials stacked together, whether it is possible to analyze and calculate the main direction strain of each layer inside without being limited by the barrier between different materials by measuring the strain in the surface layer. The article takes laminates with different combinations of carbon fiber materials as the research object and uses the measurement methods of induced extensometer and strain gauges to compare and study the accuracy of the measured values and the calculation methods of the main direction strains of the internal layers of the laminates with different material combinations. The validity of the method is verified by comparing the calculated values with the finite element software. It is shown that this method can be used to calculate the principal directional strains of the internal layers of carbon fiber laminates under different material combinations of layups.

The current work examines how flyash reinforcement, SiC p , and B 4 C p affect the tribological and mechanical characteristics of composites made of aluminum 359. Stir casting was used to create composite samples of B 4 C p , SiC p and flyash reinforced Al 359. The composites’ hardness, tensile behavior, and wear behavior were examined and contrasted with a control sample. Due to the ceramic phase, the B 4 C p , SiC p particles, and flyash reinforced Al 359 matrix are harder than the base matrix. When B 4 C p , SiC p and flyash are added to the base matrix up to 20 wt.%, the coefficient of friction increases significantly. Wear examinations were carried out on specimens under a variety of stress situations, and then five different wear processes listed here (wear groove, abrasion, delamination, oxidation, and plastic deformation) were explored. The finding of the abrasion test show that B 4 C p , SiC p and flyash enhanced composites have improved wear resistance when compared to a control specimen.

In this study, the effects of Al99.99, AlMg5 and AlZn2 wire materials coated with electric arc spray coating method on the welded EN AW 7020-T6 material on the exfoliation corrosion behavior of the substrate EN AW 7020-T6 material were investigated. The coatings obtained on the substrate were verified by XRD analysis and the coating adhesion strengths were measured according to ASTM D4541 standard. The exfoliation corrosion tests were conducted based on the ASTM G34-1 standard. No signs of corrosion were observed on the coatings in the visual examination performed after the tests. The effect of the coating’s protective properties was observed in the SEM examinations performed after the visual examination, and as expected, it was observed that neither the base material region of the substrate nor the heat-affected zone of the substrate suffered corrosion damage in all three coating types.

Green synthesis, one of the methods of obtaining metallic nanoparticles using plants, is preferred because it is simpler, eco-friendly, and economical and has the ability to reduce metallic ions using phytochemicals in its structure. This study investigates the green synthesis of CuO nanoparticles using turmeric ( Curcuma longa L. ) extract, the structural, chemical, and morphological properties of the synthesized CuO nanoparticles, and the effects on the dielectric and mechanical properties of the nano-CuO-doped epoxy nanocomposites. The total phenolic content of turmeric extract was determined using the Folin-Ciocalteu method. The structural and morphological properties of the synthesized CuO nanoparticles were characterized by UV–Vis, FTIR, XRD, FE-SEM, EDX, and TEM. The charge distribution of the nanoparticles was determined using a Zetasizer. It was determined that the shape of the synthesized CuO nanoparticles was spherical and the average particle size was 62 nm. Nanofilms and nanocomposite materials were prepared by adding the synthesized CuO nanoparticles to epoxy resin, and their effects on the dielectric and mechanical properties were investigated. An increase in the ε ′ and ε ′′ values of the doped-nanocomposite films was observed compared with those of the pure epoxy film. It was determined that nanocomposites also improved the tensile strength and hardness values.

Shot peening is a crucial surface treatment technique that significantly improves the mechanical properties of metallic components, particularly their fatigue resistance and ability to withstand corrosion cracking. This study aims to optimize the shot peening process for aviation applications by evaluating and comparing various mathematical modeling and optimization techniques. Seven mathematical models were analyzed using a neuro-regression method (NRM), among which the second-order trigonometric non-linear (SOTN) model exhibited the highest reliability, achieving R 2 values of 0.93 and 0.90 for training and testing datasets, respectively. To improve the model’s robustness, four optimization algorithms – differential evolution (DE), simulated annealing (SA), Nelder–Mead (NM), and random search (RS) – were applied to the SOTN model. Although each technique offered valuable insights, performance fluctuations across different intensity ranges necessitated the development of a hybrid optimization model that combines the strengths of all four methods. The hybrid model achieved a mean error of approximately 2.69 %, outperforming individual approaches and demonstrating strong potential for reliable shot peening optimization across a wide range of target intensities. These findings provide a comprehensive methodology for AI-based optimization of surface treatment processes in engineering applications.