International Journal of Lightweight Materials and Manufacture最新文献

The estimation of transition fatigue lifetimes for piston aluminum alloys was carried out using unsupervised machine learning (ML) with the K-means algorithm. For this purpose, an experimental dataset representing standard ISO specimens with piston aluminum alloy material, which was subjected to rotational bending fatigue tests under fully reversed cyclic load conditions, was utilized. Subsequently, the stress and fatigue lifetime data were employed to fit the algorithm of K-means clustering. Then, to enhance the K-means performance, various preprocessing methods and Kernel functions were employed to cluster fatigue lifetime and stress data. Furthermore, following the division of the data into multiple clusters, the middle cluster, which represents fatigue lifetime and stress, was identified as the transition fatigue region, and its center defines the estimated transition fatigue lifetime. Ultimately, the transition fatigue lifetimes were determined using the Coffin–Manson–Basquin equation for piston aluminum alloys and compared to the estimated transition fatigue lifetimes, along with the calculation of relative errors. The obtained results indicated that, among the different models employed in this study, the polynomial Kernel K-means clustering algorithm proved to be the most efficient for clustering data within stress and number of cycles plots (S–N plots). Moreover, employing the K-means algorithm with a polynomial Kernel function and five cluster numbers yielded the most accurate estimation of transition fatigue lifetime for piston aluminum alloys, exhibiting the lowest relative error.

Dimensional distortion and instability in the milling process of aluminum alloy parts can significantly increase production costs and result in defective parts. Therefore, distortion mitigation has long been a central focus of aerospace industry researchers. This article aims to investigate the effect of axial ultrasonic-assisted milling on distortion. In this study, the machining parameters effect in conventional milling (CM) and ultrasonic assisted milling (UAM) were experimentally and statistically investigated on distortion and milling force, and the results were subjected to a comparative analysis. Experiments provided compelling evidence of the technical advantages offered by axial ultrasonic-assisted milling, demonstrating its efficacy in reducing both milling force and distortion when compared to conventional milling. Furthermore, our study established a direct relationship between milling force and distortion. Applying the axial ultrasonic-assisted vibration resulted in a notable 29% reduction in cutting force compared to conventional milling. Additionally, UAM exhibited a reduction in distortion by approximately 21%. These findings have significant implications, particularly in improving the flatness tolerance of the workpiece, thereby yielding components free from waves and warpages.

In this study, the effect of resistance spot welding (RSW) and laser beam spot welding (LBSW) processes on evolution of microstructure, load endurance capabilities, heat affected zone (HAZ) softening, and corrosion resistance of ultra-high-strength (UHSS) steel joints welded in lap joint design is investigated. The UHSS sheets of dual phase 1000 grade (UHSDP1000) having 1.20 mm thickness were joined using the RSW and LBSW parameters optimized by response surface methodology (RSM). The microstructural features of welding regions of RSW and LBSW joints were studied using optical microscopy (OM). The load endurance capabilities of RSW and LBSW joints were assessed using the tensile shear failure load (TSFL) and cross-tensile failure load (CTFL) tests. The ruptured surfaces of TSFL and CTFL tested samples were examined utilizing scanning electron microscopy (SEM). The microhardness distribution of divergent regions of RSW and LBSW joints was evaluated and imputed to the TSFL and CTFL failure of joints. The corrosion resistance of RSW and LBSW joints was analyzed using potentiodynamic corrosion and immersion corrosion tests. The RSW joints showed 183% and 62.79% greater TSFL and CTFL endurance capabilities than LBSW joints. The TSFL and CTFL endurance capabilities of LBSW joints are inferior to RSW joints due to the smaller load bearing area. It causes the stress concentration in FZ and HAZ of LBSW joints. The RSW joints and LBSW joints disclosed TSFL and CTFL failure in button pull out rupture mode with tearing of HAZ. The failure of RSW and LBSW joints in HAZ is due to the softening caused by martensitic tempering and coarsening of grains. The LBSW joints disclosed inferior resistance to corrosion than RSW joints due to the higher martensite content which contributes to greater fraction of favorable pitting sites and decreased corrosion resistance.

The AA6082-T6 was experimentally studied in the present research with respect to the drilling performance. Drill diameter, cutting speed and feed rate were examined, using a full factorial design. Mathematical modelling of the process was carried out using the Response Surface Methodology (RSM) as well as the Artificial Neural Network (ANN) techniques. The output results in terms of cutting force, torque and surface roughness, revealed high levels of correlation between the experimental and the predicted data. Specifically, the Mean Absolute Percentage Error (MAPE) values using RSM compared to the ones of the experiments, were equal to 2.14%, 3.49% and 6.16% for F_z, M_z and R_a respectively. The equivalent MAPE between the ANN and the experiments were found to be 2.19%, 1.82% and 2.85% accordingly. Moreover, the most significant terms were revealed, being the interaction D × f for the thrust force and the torque with contribution percentages equal to approximately 44% and 42% respectively, and the term D² for the surface roughness with 51%. The evaluation of the machining parameters, identified their significance, enabling the selection of the optimal cutting parameters, which were obtained by the desirability function, taking into account the importance of the generated surface quality and the reduction of cost. The solutions given by this approach, pointed out the Ø9 tool, coupled with V_c = 50 m/min and f = 0.15mm/rev as a well-balanced combination, whereas the Ø9.9 tool used under the same conditions, yielded the best possible surface quality (appr. 0.2 μm).

The effects of salt water exposure at deep ocean depth pressures when coupled with low temperatures on the material characteristics of three unique additively manufactured polymers has been investigated through a detailed experimental approach. The polymers in the study were manufactured utilizing both Vat Photopolymerization and Material Extrusion printing techniques. The Material Extrusion process was utilized to produce material specimens of Stratasys ULTEM 9085 and Markforged Onyx while the Vat Photopolymerization process was used to produce specimens of Accura ClearVue. The ULTEM 9085 and Markforged Onyx are filament based polymers and the ClearVue is a liquid based resin. The specimens were first submerged in a high pressure, salt water bath of 3.5% NaCl solution at 34.5 MPa (5000 lb/in²) for a total exposure time of 60 days to determine the water absorption characteristics. Subsequent to the salt water exposure at high pressure, the specimens were evaluated to determine changes in tension, compression, flexure, and in-plane fracture properties. To determine the effects of water saturation and low temperature coupling, the mechanical testing was performed at temperatures of 20 °C, 0 °C and −20 °C in both dry and saturated conditions. Additionally, non-destructive testing in the form of TeraHertz and FIRT imaging was conducted to analyze the physical material changes through the thickness of the material due to the saline water absorption. To quantify the change in material storage and loss moduli properties, Dynamic Mechanical Analysis (DMA) characterization was performed on each of the AM polymers in dry and saturated states. The DMA testing also quantified changes in the Glass Transition Temperature because of salt water exposure. In summary, The current study investigates the effects of coupled long term/high pressure salt water exposure with low temperatures on the mechanical and material characteristics of three unique AM polymers by: (1) immersing the materials in a salt water solution at 34.5 MPa for 60 days, (2) Conducting post exposure mechanical testing on the materials at 0 °C and −20 °C with comparisons to 20 °C testing on dry specimens, and quantifies changes in material properties through DMA experiments. The results from all testing in the study show that high pressure salt water exposure when coupled with low temperatures has unique effects on each of the materials considered in the study and careful consideration to each parameter must be given based on the material type when components will be employed in marine operations.

The microstructure of a linear friction welded joint of 7050 aluminum alloy was investigated through optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The analysis focused on grain boundary types, microstructure, and mechanical properties of the joint. The results reveal that fine equiaxed crystals are generated in the welded zone through dynamic recrystallization. The average grain size is 6.8 μm, with a volume fraction of large angle grain boundaries reaching 69.5%. The microstructure primarily consists of Cube {001}<100> texture, {111}<110> Brass recrystallization texture, and a small amount of copper {112}<111> deformation texture. The thermo-mechanically affected zone (TMAZ) presents a linear structure with an average grain size of 15.8 μm and a volume fraction of 36.1% at large grain boundary, resulting in a deformed Brass {011}<211> texture and a small amount of {236}<385> as well as {111}<110> Brass recrystallization texture. The welded joint exhibits a tensile strength of 492 MPa and a yield strength of 380 MPa, which represents 94.2% and 78.5% of the base material, respectively. Furthermore, the elongation of the joint is 10.2% and 98% of the base material, respectively. The fracture of the tensile sample is observed in the TMAZ, showing good mechanical properties with a mixed fracture mode with some degrees of ductility and brittleness.

Friction stir welding (FSW) is a solid-state welding process that is suitable for joining hardly weldable metals such as aircraft AA2024-T3 aluminum alloy. Despite FSW owns many advantages, however, some problems still arise, especially welding residual stress which influences the weld fatigue performance. In the present work, in-process transient thermal tensioning (TTT) treatment was applied to the FSW process of AA2024-T3 aluminum alloy by putting two symmetrical heaters at the sides of the weld line at distances of 25 mm, 40 mm, and 55 mm. The FSW was conducted at the tool rotational speed of 1500 rpm and tool traveling speed of 30 mm/min whereas the heating temperature was set at 200 °C. Subsequently, changes in microstructure, strength, hardness, residual stress, and fatigue crack propagation rate under TTT treatment were evaluated. The results showed that the use of TTT generated peaks of tensile residual stress along the heater passage which changed the residual stress distributions. It was found that the best fatigue crack propagation resistance of the weld occurred at the heater distance of 25 mm which was attributable to the compressive residual stresses present in the weld region induced by thermal tensioning combined with re-precipitation during welding.

Short fibers of Agave Americana (AA) was extracted from its plant leaf, was chemically treated with Ac₂O, HCOOH, H₂O₂, KMnO₄ and NaOH, and then characterized by Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), thermo-gravimetric/differential thermo-gravimetric (TGA/DTG), and field emission-scanning electron microscopy (FE-SEM). PVA stabilized copper nanoparticles from chemical reduction method was characterized using field emission-scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDAX), powder X-ray diffraction (PXRD), Dynamic light scattering analysis (DLS), UV–visible absorption spectroscopy, Fourier Transform infrared (FT-IR) spectroscopy and Thermogravimetric analysis/differential thermogravimetry (TGA/DTG). Bio-composites (AA + Polyester Resin (PE) and hybrid nano bio-composites (AA + Polyester Resin (PE) + Cu) were prepared from the untreated and treated AA fibers and further characterized. The synergistic effect of chemical treatment on morphological (SEM), thermal (TGA/DTG), mechanical properties (flexural, tensile, impact and compressive strength) followed by % water absorption were examined. The average surface roughness values (Ra) of chemical treated fiber was identified to be in decreasing manner along with compression strength of biocomposite in the order of untreated (10.74 μm, 44.01 MPa) > NaOH (8.55 μm, 45.07 MPa) > HCOOH (3.49 μm, 24.10 MPa) Ac₂O (3.24 μm, 22.10 MPa) > H₂O₂ (2.51um, 17.9 MPa) > KMnO₄ (1.52 μm, 15.1 MPa) treated fibers. Subsequently, the addition of 2s@PVA led to reverse the order namely, the compressive strength of the bionanocomposites were Untreated (10.74 μm, 9.0 MPa) < NaOH (8.55 μm, 0.1 MPa) < HCOOH (3.49 μm, 3.6 MPa) < Ac₂O (3.24 μm, 7.6 MPa) < H₂O₂ (2.51um, 13.3 MPa) < KMnO₄ (1.52 μm, 44.1 MPa) treated fibers. Similarly, the biocomposite where the fibres were treated with NaOH, HCOOH were more rough and had, good interconnection between fiber/PE matrix along with enhanced mechanical properties. On addition of nanobiocomposite, only KMnO₄ treated fiber composite possed significant mechanical properties. Therefore, mixing CuNPs@PVA with KMnO₄ treated fibers led to significant boost to the mechanical properties and minimised the % water absorption properties when compared to the untreated AA/PE biocomposites. The KMnO₄ treatment of the AA fiber and addition of copper nanoparticles caused the enhancement of thermal properties, tensile strength and flexural strength. But, these nanobiocomposites were observed to have low impact strength; while, H₂O₂ treated nanobiocomposites had highest impact strength. The chemical treatment of the AA fiber with NaOH, Ac₂O and KMnO₄ developed the water resistance of th