Key Engineering Materials Vol. 988

Abstract: The purpose of the work is to quantify and predict the influence of inhomogeneity of local properties on the overall behavior of the selected casting aluminum wheel and knuckle in different loading cases. Smooth and notched tensile specimens and torsion specimens are extracted from different positions in the wheel and knuckle and tested. The dependences of the flow stress, the fracture strain, and the S-N curve on position for specimen extraction are evaluated. Metallographic investigations are performed to reveal the relations between microstructure/microdefects and the mentioned properties. A damage model based on a triaxiality-dependent fracture strain is calibrated and used to simulate the specimens and component tests. The simulations of static wheel tests and knuckle fatigue tests are performed with position-dependent material parameters. The prediction of the component tests is compared with the experimental results.

Abstract: In the present study, it is aimed to investigate the influence of quench rate on the hardness and electrical conductivity that obtained after artificial aging by using Jominy End Quench test method. The Jominy End Quench test bars were solution heat treated at 560°C for 3 hours. After solution heat treatment, water, spray, and air quenching medias were used in order to obtain different quench rates. After the quench, quench rate determination, hardness and electrical conductivity measurements were performed for three different quenching medias. Then, artificial aging heat treatment were applied to all samples at 180°C for 8 hours to understand the effect of quench rate on aging process. The relationship between quench rate, hardness and electrical conductivity have presented.

Abstract: Materials characterization and the knowledge of their elastic-plastic behavior are of fundamental importance for the design of industrial manufacturing processes. Nowadays, FEM simulation is the main tool used to optimize product quality and minimize scraps, and the numerical codes have evolved over the years to obtain accurate solutions with reduced computational times. Nevertheless, in order to perform reliable simulations, it is necessary to include accurate modeling of the material flow stress. Hot torsion is a powerful method for the characterization of the material flow stress because, tests can be carried out at constant speeds and temperatures, reaching large strain values, and thus getting over the limits of compression and tensile tests. In this paper the hot torsion characterization applied to AA6082 alloy is presented: tests were performed with equivalent strain rates of 0.01, 0.1, 1, and 10 s^-1, in the temperature range from 440 to 550 °C (from 713.15 to 823.15 K). The results are presented in terms of equivalent stress vs equivalent strain. Finally, the material flow stress curve was predicted by the Hyperbolic sine model and Hensel-Spittel law, and the material parameters A, m_1-9 are provided for the temperature expressed in °C and K.

Abstract: Hot tearing is a well-known limitation when trying to maximize the throughput rate in aluminium extrusion. In the present work an analytical modelling framework is presented which can be used to predict the maximum extrusion speed that can be applied in production without formation of this type of surface defect. The modelling framework allows almost instantaneous estimates on the resulting productivity in terms of maximum extrusion speed. This is obtained by developing an analytical model for the maximum temperature at the die exit which incorporate the effect of alloy composition and billet processing. The results are consolidated into extrusion limit diagrams, mapping the maximum allowable extrusion speed as a function of billet pre-heat temperature, alloy composition, and homogenisation heat treatment. The calculated temperatures and extrusion limit diagrams obtained from the analytical model are compared with measured temperatures and critical extrusion speeds from extrusion tests of various 6xxx series alloys for a simple rod-shaped geometry. The comparisons indicate that the presented modelling approach gives sufficiently accurate predictions for future application in optimisation of alloy composition and process parameters in extrusion of profiles.

Abstract: The Extrusion Benchmark 2023 was focused on the evaluation of different die design strategies for the manufacturing of AA6082 hollow tubes (40 mm external diameter and 4 mm thickness) through a porthole die with 3 openings. The extrusion process was monitored in industrial environment in terms of press load, profiles speed, profiles exit temperature, and die temperatures under different processing conditions (air quenching, water quenching, nitrogen die cooling). Extruded profiles were then analyzed in terms of seam weld quality, charge weld extension and microstructure evolution for both air/water quench and presence/absence of nitrogen cooling. The results of the study are aimed at validating FEM simulation outputs in the context of the International Conference on Extrusion and Benchmark (ICEB).

Abstract: The aim of this study was to determine the optimal configuration of silicon carbide-ultrahigh molecular weight polyethylene (SiC-UHMWPE) plates to effectively withstand 0.5 caliber Browning Machine Gun (BMG) projectiles. Six composite plates with varying thicknesses were 3D modeled and assessed for ballistic resistance using finite element analysis in Ansys Explicit Dynamics simulation software. These plates were subjected to high-velocity impacts at 930 m/s using 7.62 mm projectiles. The findings revealed that an 11 mm SiC/80 mm UHMWPE plate provided comparable bullet-stopping performance to a standard 8 mm steel 4340/60 mm UHMWPE plate, but with a significantly lower areal density. The primary mode of failure observed in penetrated samples was petaling, consistent with known behaviors of composite armor under high-impact conditions.

Abstract: This study investigates the ballistic resistance of composite plates composed of a silicon carbide (SiC) strike face and ultra-high molecular weight polyethylene (UHMWPE) layers against 7.62 mm NATO caliber projectiles using Ansys Explicit Dynamics. Five ballistic plate samples were numerically modeled, featuring 40 to 60 UHMWPE layers and a 4 mm SiC strike face. The simulation assessed the plates' response, including backface signature, bullet penetration depth, absorbed kinetic energy, and deformation mechanisms. The findings revealed that increasing the UHMWPE thickness reduces both the backface signature and bullet penetration depth. Plates with 50 to 60 layers of UHMWPE met level III NIJ standards, demonstrating lower backface signatures and bullet penetration compared to those with 40 or 45 layers. Thicker UHMWPE layers were associated with reduced deformation, with the plate featuring 60 layers of UHMWPE and an overall thickness of 25 mm emerging as the optimal configuration for level III ballistic protection.

Abstract: In response to the escalating global water crisis, this study introduces the development of polyamide-modified membranes (PA-PES, PA-PP, and PA-PTFE) through interfacial polymerization to enhance the efficiency of a passive solar desalination system. FTIR analysis and morphological characterization showed that a thin polyamide film formed above the modified membranes using m-phenylene diamine (MPD) and trimesoyl chloride (TMC). Notable improvements were observed in its productivity and distillate salinity by integrating these modified membranes into the membrane distiller of the system. Mainly, the PA-PES membrane achieved productivity of 764.56 ml/m²-h and reduced salinity to as low as 2 g NaCl/L. Despite challenges in salinity reduction, possibly due to residual chlorides, this study demonstrates the potential of polyamide-modified membranes in advancing solar-driven desalination, offering a promising solution to mitigate global water scarcity. This research paves the way for further advancements in sustainable desalination technology, emphasizing the need for continued optimization and exploration of membrane-based systems.

Abstract: Electrochemical research is devoted to the development of a method of processing secondary raw materials containing tungsten in the form of a pseudoalloy of the carbide type WC–Co in sulfate solutions. The target processing products are: powders of tungsten oxides of lower oxidation states, which can be reduced to metallic tungsten with lower costs. Using the methods of linear and cyclic voltammetry, it was established that the selective dissolution of the cobalt component of the pseudoalloy in the studied solutions occurs at potentials more positive than 0.2 V, carbon is removed from the working electrode at a potential > 0.8 V. At the same time, tungsten is oxidized to the higher oxide WO₃. It was determined that in sulfuric acid, with an increase in its concentration from 1 to 5 mol∙dm-3, the current density decreases, which is associated with the formation of a solid surface layer of tungsten oxide on the surface of the anode, which passivates the surface. It was established experimentally that when adding 1 mol∙dm^-3 of H₂SO₄ hexamine (C₆H₁₂N₄) with a concentration of 0.9 mol∙dm^-3 to a solution, it is possible to block the process of formation of a passivating film and obtain powders of tungsten oxides of lower oxidation states.