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Friction stir processing (FSP) is a modern manufacturing strategy for improving the surface characteristics of materials by modifying their surface via localized plastic deformation. This research focuses on optimization process parameters for tungsten carbide-reinforced 6061 aluminum alloy surface composite using FSP. The effect of the process parameters including tool rotational speed, transverse feed, number of passes, and tungsten carbide particles volume fractions, on ultimate tensile strength (UTS) and grain size of fabricated AA6061/WC surface nanocomposites are investigated. For four factors and three levels, the L27 Taguchi technique is used to formulate the experimental design. The analysis of variance (ANOVA) is used to determine the significance and the percentage contribution of each parameter. The desirability approach is used to optimize the process parameters in terms of tensile strength and average grain size. The results indicate that the proper selection of FSP parameters results in a homogeneous distribution of the WC particles throughout the matrix thereby producing a defect-free AA6061/WC nanocomposite without voids. Also, the severe plastic deformation and heat generation during FSP causes the breaking of coarse particles, WC particles, elimination of porous holes and creates an ultrafine grain-sized structure via dynamic recrystallization. Furthermore, it was concluded that the transverse feed is the most significant factor for ultimate tensile strength with 40.1% contribution whereas the number of passes is the most significant factor for grain size with a 34.7% contribution. The optimum combination of the current process parameters is found to be 1800 rpm rotation speed, 120 mm/min transverse feed, 4.3636% volume fraction, and 3- pass for optimum values of UTS and grain size. The surface composite developed in this work is considered appropriate material for applications requiring lightweight and improved surface properties, such as aerospace, automotive, marine, defense and transportation industries.

The present study is an attempt to investigate the tribological behavior of friction stir processing (FSP) AA6061-T6 alloy reinforced with boron carbide (B4C) particles. The surface composites were developed to investigate wear performance and surface roughness under dry sliding conditions. The experiments were conducted using response surface methodology (RSM) to examine the effects of various B4C volume fractions, applied loads, and sliding distances. All combinations of reinforcements in AA6061-T6 hybrid composites show a good improvement in the wear properties. The results show that the wear behavior of composites is significantly impacted by the incorporation of B4C particles. This is mostly owing to the uniformity that the B4C particles developed when they distributed the reinforcements evenly in the AA 6061-T6 matrix. Analysis of variance, main effect and three-dimensional plots were used to quantify the effects of dry sliding parameters on tribological properties. The findings showed that the optimal parameters for the effective reduction of specific wear rate and coefficient of friction were a volume fraction of 10%, an applied load of 20 N, and a sliding distance of 500 m. To minimize surface roughness, the optimal test conditions were found to be 10% volume fraction, 40 N applied load, and 2500 m sliding distance. The wear surface was analyzed using energy dispersive spectroscopy (EDX) and scanning electron microscopy (SEM). The results showed that oxide layer formation was present on the wear surface and adhesive wear was the primary wear mechanism.

Friction stir processing (FSP) is a solid-state microstructural modification technique that has recently become an effective tool to refine microstructures and improve the mechanical properties of metals. In the current study, optimization of FSP parameters, including tool rotational speed, transverse feed, number of passes, and tungsten carbide (WC) nanoparticle volume fractions on mechanical and wear properties of the fabricated AA6061/WC nanocomposite was studied. Optical microscopy and scanning electron microscopy are used for microstructural observations. The process parameters are optimized using the Taguchi technique for single responses towards microhardness and weight loss and the Desirability approach for both responses. The percentage contribution of process parameters is estimated using analysis of variance. The microstructure observation shows that the proper selection of FSP parameters leads to a homogeneous dispersion of the WC particles throughout the matrix, thereby producing a defect-free AA6061/WC nanocomposite without voids. Also, the severe plastic deformation and heat generation during FSP cause the breaking of coarse particles, WC particles, and porous holes and create an ultrafine grain-sized structure via dynamic recrystallization. The results indicated that the microhardness value of the processed composite was found to be 144 VHN, which is 39.81% higher than that of the base metal. Also, the weight loss of all samples decreased as compared to the base metal. Also, it can be observed that the number of passes is the most significant factor for microhardness, with a 40.1% contribution, and for minimum weight loss, the volume fraction is the most significant factor, with a 56.94% contribution. The optimum process parameter combination was found to be 1800 rpm rotation speed, 120 mm/min of transverse feed, 6% volume fraction, and 3 passes that resulted in obtaining optimum values for micro hardness and weight loss. The surface composite developed in this research is considered a suitable material for applications demanding lightweight and enhanced surface properties, including automotive, aerospace, marine, defense, and transportation industries.

This paper presents a case study that aims to develop a hardware design for the pc to the satellite, supported fault-tree design and calculations of dependableness. The on-board pc of a satellite, inserted into the on-board management system, has functions of receiving, process and distribution of commands to the subsystems and payload of the satellite; and exploit, formatting, storage and transmission of measurement from subsystems and payload. The most necessities of associate on-board pc are high dependableness, capability of real time process, resistance to radiation, and minimizing power consumption, volume and mass. Enlarged dependableness is achieved by the fault tolerance technique that relies on adding redundancy to the system, or the utilization of elements with high price of individual dependableness. During this work, hardware redundancy techniques are thought-about. First, a pc is meant and its dependableness is calculated, for a mission of one year period. Mission dependableness goal isn't earned during this calculation. So as to extend dependableness, two kinds of fault tolerant redundant architectures are analyzed, with their various reliabilities calculated for the identical amount of the mission.