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Strolling is a complex activity that requires the synchronization of the brain, anxiety, and muscles, as well as rhythmic movement of the lower limbs. Gait may be abnormal if coordination is disrupted. As a result, exoskeletons should be used to treat it effectively. The connection and other systems contained in the exoskeletons could be used to mimic the behavior of the human lower leg. These mechanisms are created utilizing complex traditional methods. This study proposes a new gait-inspired method based on a genetic algorithm (GA) for synthesizing a four-bar mechanism for exoskeletons. For each phase of the gait, the trajectory is calculated and merged using optimization algorithms. Each phase of the trajectory passes through 10 precision points, for an entirety of 20 precision points in 1 gait cycle. For the problem under consideration, it is discovered that the GA outperforms other literature techniques. Finally, the proposed design for a lower limb exoskeleton is depicted as a solid model. Furthermore, the generated link-age accurately tracks all the transition points, and the simulation of the planned linkage for one gait cycle has been illustrated using a stick diagram.

The main aim of the current work is to investigate the effect of equal channel angular pressing (ECAP) processing parameters, namely, number of passes, ECAP die angle, route type, and processing temperature on the mechanical and electrical properties of pure copper (Cu). The finite element method was used to simulate the homogeneity of stress and plastic strain distribution during ECAP processing. The response surface methodology (RSM) was used to identify the optimum ECAP processing parameters by analyzing the impact of ECAP conditions on responses. A second-order regression model and analysis of variance were created to analyze the ECAP condition of optimum responses. A genetic algorithm (GA) was also applied to optimize the ECAP condition. Finally, a hybrid RSM–GA was created to improve the optimization of ECAP responses and corresponding conditions evaluated using GA. The developed models were validated and compared with the experimental findings to prove that they are reliable as predictive tools. The optimization findings revealed that route Bc was more effective in improving the hardness, yield stress, ductility, and impact energy whereas route A was more effective in improving the ultimate tensile strength and the electrical conductivity of the Cu billets. Furthermore, the optimum die angle, number of passes, and processing temperature for the mechanical and electrical properties were also identified individually.

This study aims to enhance the practical performance of PVDF/ZnO and PVDF/TiO2 composite coatings known for their distinctive properties. The coatings, applied through spray coating with PVDF and ZnO or TiO2 nanoparticles on glass, steel, and aluminum substrates, underwent a comprehensive evaluation. Surface wetting properties and morphology were respectively evaluated using a technique involving liquid droplets and an imaging method using high-energy electrons. Potentiodynamic polarization was used to compare corrosion resistance between coated and bare substrates. Nanoindentation was used to assess coating hardness, and bonding strength was subsequently quantified. The results revealed that PVDF/ZnO composite coatings had higher water contact angles (161 ± 5° to 138 ± 2°) and lower contact angle hysteresis (7 ± 2° to 2 ± 1°) compared to PVDF/TiO2 and PVDF coatings. Moreover, corrosion tests demonstrated superior protection for steel and aluminum surfaces coated with superhydrophobic PVDF/ZnO. Nanoindentation indicated enhanced mechanical properties with TiO2 nanoparticles, with adhesion results favoring TiO2 over ZnO nanoparticles. [ABSTRACT FROM AUTHOR]

This study comprehensively investigates the impact of various parameters on aluminum matrix composites (AMCs) fabricated using the powder metallurgy (PM) technique. An Al-Cu matrix composite (2xxx series) was employed in the current study, and Al2O3 was used as a reinforcement. The performance evaluation of the Al-4Cu/Al2O3 composite involved analyzing the influence of the Al2O3 weight percent (wt. %), the height-to-diameter ratio (H/D) of the compacted samples, and the compaction pressure. Different concentrations of the Al2O3 reinforcement, namely 0%, 2.5%, 5.0%, 7.5%, and 10% by weight, were utilized, while the compaction process was conducted for one hour under varying pressures of 500, 600, 700, 800, and 900 MPa. The compacted Al-4Cu/Al2O3 composites were in the form of cylindrical discs with a fixed diameter of 20 mm and varying H/D ratios of 0.75, 1.0, 1.25, 1.5, and 2.0. Moreover, the machine learning (ML), design of experiment (DOE), response surface methodology (RSM), genetic algorithm (GA), and hybrid DOE-GA methodologies were utilized to thoroughly investigate the physical properties, such as the relative density (RD), as well as the mechanical properties, including the hardness distribution, fracture strain, yield strength, and compression strength. Subsequently, different statistical analysis approaches, including analysis of variance (ANOVA), 3D response surface plots, and ML approaches, were employed to predict the output responses and optimize the input variables. The optimal combination of variables that demonstrated significant improvements in the RD, fracture strain, hardness distribution, yield strength, and compression strength of the Al-4Cu/Al2O3 composite was determined using the RSM, GA, and hybrid DOE-GA approaches. Furthermore, the ML and RSM models were validated, and their accuracy was evaluated and compared, revealing close agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Aluminum base alloys containing chromium (Cr) and zinc (Zn) were produced using extrusion and powder metallurgy techniques. Cr additions ranged between 5 to 10 wt. %, while Zn was added in an amount between 0 and 20 wt. %. Heat treatment processes were performed during powder metallurgy process, at different temperatures, followed by water quenching. Similar alloys were extruded with an extrusion ratio of 4.6 to get proper densification. Optical microscopy was used for microstructure investigations of the alloys investigated. The element distribution microstructure study was carried out using the Energy Dispersive X-ray analysis method. Hardness and tensile properties of the investigated alloys have been examined. Wear resistance tests were carried out and the results were compared with these of the Al-based bulk alloys. Results showed that the aluminum base alloys, containing 10 wt. % Cr and heat treated at 500 °C for one hour followed by water quenching, exhibited the highest wear resistance and better mechanical properties. [ABSTRACT FROM AUTHOR]

Iron powders having average particle sizes of ~40 μm are mechanically mixed thoroughly with aluminum powders ranging from 1 to 10 in wt. %, with an average particle size of ~10 μm. Two different powder metallurgy (PM) techniques, cold and hot pressing, are used to study the effect of the additive element powder on the mechanical properties, wear properties, and the microstructure of the iron based alloys. The hot pressing technique was performed at a temperature reaching up to 500 °C at 445.6 MPa. The cold pressing technique was performed at 909 MPa at room temperature. By increasing the Al content to 10 wt. % in the base Fe-based matrix, the Brinell hardness number was decreased from 780 to 690 and the radial strength from 380 to 228 MPa with reductions of 11.5% and 40%, respectively. Improvement of the wear resistance with the increase addition of the Al powder to the Fe matrix up to five times was achieved, compared to the alloy without Al addition for different wear parameters: wear time and sliding speed. [ABSTRACT FROM AUTHOR]