Applied Mechanics and Materials Vols. 592-594

Abstract: Al7075 and Al₂O₃ powders were synthesized via high-energy ball mill for 15 h. Al7075 powders were mixed with 10 vol. % Al₂O₃, compacted by cold uniaxial compaction at 400 MPa. The green pellets were degassed at 350 oC for 30 min, and then sintered in the temperature of 600 oC under argon atmosphere for 120 min. It was shown that better density, vickers micro hardness and corrosion resistance were achieved due to refinement of grain size. HRTEM micrographs demonstrated a uniform distribution of Al₂O₃ particles in aluminium alloy and equilibrium η (MgZn₂) precipitates along the grain boundaries.

Abstract: In recent years, stringent requirements of material quality in automotive and aerospace industries have necessitated the development of lightweight aluminum alloys. In this context, it is known that the metal–matrix composites offer a spectrum of advantages that are important for their selection and use as structural materials. A few such advantages include the combination of high strength, high elastic modulus, high toughness and impact resistance, low sensitivity-to changes in temperature or thermal shock, high surface durability, low sensitivity to surface flaws, high electrical and thermal conductivity, minimum exposure to the potential problem of moisture absorption resulting in environmental degradation, and improved fabricability with conventional metal working equipment Metal matrix composites (MMC) are generally produced either by liquid metallurgy or powder metallurgy techniques. Stir casting is one of the most inexpensive tools for the production of particulate metal matrix composites . It is simplest and most commercially used technique for casting MMCs. This involves incorporation of ceramic particulate into liquid aluminum alloy in molten state and allowing the mixture to solidify. Here, the crucial thing is to create good wetability between the particulate reinforcement and the liquid aluminum alloy. In this proposed work , composites of Al7075 with SiC were fabricated using Stir casting method by using both upward and downward pouring methodology .The main objective of this research work are to achieve uniform distribution of SiC particles in the aluminum alloy matrix , characterization and analysis of mechanical properties of composites formed . Experiments were carried out with different stirring speeds and specimen of different %wt of SiC were cast . Microstructure , Tensile strength and hardness values were found by conducting the corresponding tests and results were analyzed and compared . Key words - MMCs , Stir casting , Wire cut EDM , SiC reinforced metal matrix composites

Abstract: In the present work, an attempt has been made to explore the general microstructural characteristics and mechanical properties of titanium-titanium boride (Ti-TiB) composites (20 and 40 vol.% TiB reinforcement in Ti matrix) processed by Vacuum Sintering. The microstructures of the composites were investigated using electron probe micro analysis, scanning electron microscopy and X-ray diffraction. Obviously, the elastic modulus, shear modulus and hardness are found to increase with increase in volume fraction of titanium boride. The effects of titanium boride reinforcements on elastic properties and microhardness are discussed.

Abstract: The effect of intermetallic phases and grain size on ductile to brittle transition temperature of Aluminium-Iron alloy (Al–11% Fe) was investigated in this research work. An Izod impact testing method was adopted to study the DBTT in the temperature interval of 77 K to 373 K. The ductile-brittle transition points: fracture transition plastic (FTP), fracture-appearance transition temperature (FATT), impact energy transition temperature (IETT), fractional surface area of cleavage (brittle) and fibrous (ductile) fractures and grain size of the samples were also determined. The fracture toughness of Al-Fe alloy found decreasing with temperature in contrast to conventional materials. The fractographic investigation revealed that the microstructural changes play a major role in determining the fracture toughness of these alloys. Annealing of these samples slightly improved the fracture toughness as the spherical morphology of intermetallic particles resists the crack propagation.

Abstract: Friction stir processing (FSP) is a solid-state process leading to very significant microstructural modifications. Despite the large number of studies, most of the work that has been done in the FSP field focuses on microstructural evolution, tensile properties, hardness, fatigue strength, corrosion resistance etc. However there is not much information available on correlation of FSP parameters with evolution of defect free processed zone. In order to produce a defect free processed zone, selecting the best processing parameters is very important. In this investigation, the effect of two main FSP parameters (such as tool rotational speed which was kept constant and tool transverse speed which was varied) on the formation/ evolution of defect free processed zone was studied. It is found that at a tool rotational speed 600 rpm and a traverse speed of 12 mm/min the processed zone is defect free. Numerous investigations have been conducted to understand material flow behavior during FSW/FSP. However, the flow process of material during FSW/FSP is still not well-understood, and different explanations have been proposed. In this investigation an attempt has been made to understand the flow of material during FSP and it is reported.

Abstract: Recent developments in cutting tool technology and its environmental impact have made significant revolutions in hard turning process thereby increasing the productivity level and enhancing the surface integrity of machined components competitively. In this experimental work, the machinability aspects, surface finish and tool life w`ere investigated during hard turning of hardened AISI D3 tool steel work materials with wiper geometry ceramic inserts under eco-friendly compressed air cooling environment. The process variables such as cutting speed, feed rate, tool nose radius, hardness levels of work materials and compressed air pressure were considered for this study. Since the tool nose design influences the machinability aspects, the cutting tool nose radius was considered as one of the vital process parameters. The design of experimental sequence and analysis of experiment data were carried with the help of Design Expert, DOE software. The combinations of Taguchi L16 orthogonal array and ANOVA technique have been applied for evaluating the process outcomes with reference to cutting variables. From the current experiment results, it is observed that combination of wiper ceramic insert with large nose radius and lower levels of compressed air pressure and work piece hardness (HRC) were resulting in higher surface quality with prolonged cutting tool life.

Abstract: The main aim is to control thermal expansion in aluminium piston at high working condition. A plasma sprayed ceramic coating (TBC) is applied on the piston crown as a top coat and NiCrAl is applied as the middle layer as bond coat to improve the addition strength between the top coat and the metal subtract layer as AlSi alloy; we introduce a thermal slot on the piston shrink to regulate the heat flow in piston and make it cooler. We analyse the piston with these two implementations to determine the thermal analysis of the piston. The results can be shown in the various comparisons of coating thickness of top coat with thermal slots on the piston shrink. Increase in coating thickness reduces the stress in the coatings. It is observed that 85°C increase in 0.8mm coat than the ordinary piston.

Abstract: Combined extrusion-forging is used in the manufacturing of a wide range of engineering components. Due to the complexity of the forming process and because of so many process variables, it is difficult to predict the forming load required to manufacture a given component. It is very costly to conduct different trail runs to know the metal flow patterns, and for redesigning of tool and die setup, etc. The present paper deals with the Finite element analysis of combined forward and backward extrusion-forging process for the product shape socket wrench. Two types of socket wrenches, Square-square type and hexagon-square type have been taken for the present analysis. The modelling has been done by using 3D modelling software CATIA and simulation through the Finite element based package DEFORM 3D software. The forming load can be estimated by the results obtained from the Finite element analysis through DEFORM 3D software.

Abstract: In the present work, an attempt has been made to monitor the tool condition status during microturning of aluminium alloy (AA 6061) using multiple sensors such as cutting force dynamometer, acoustic emission (AE) and accelerometer. The tool wear (nose wear) is correlated with surface roughness (R_a), chip width, thrust force (F_x), tangential force (F_y), feed force (F_z), AE_RMS and vibration signals. It is observed that R_a, chip width and cutting forces are increased with increase in the tool wear. Among the cutting forces, the tangential force (F_y) is found to be more sensitive to the tool wear status compared to that of the thrust force (F_x) and feed force (F_z). From the signal analysis, it is observed that during machining with good tool condition, the dominant frequency of the AE_RMS and vibration signals are found to be 81 kHz-110 kHz and 2.07 kHz-3.84 kHz respectively, whereas with the worn out tool the dominant frequencies are shifted to higher levels. Chip morphological studies indicated that favourable type of chips are formed upto 40^th minute and unfavourable chips are observed from 41^st minute to 60^th minute.

Abstract: This paper presents wavelet based recognition of the machined surfaces namely turned, ground and shaped surfaces from the images acquired using Computer Vision System. Selection of mother wavelet has been done based on the peak signal to noise ratio (PSNR) value using Discrete wavelet transform (DWT) which has been used for feature extraction. Artificial neural network has been used to recognize the machined surfaces.