Applied Mechanics and Materials Vols. 592-594

Abstract: The addition of zinc to aluminum with magnesium or copper produces heat treatable alloys of highest strength which can be used for structural applications. This work is an attempt to investigate any improvement in hardness and fracture toughness by coating aluminum 7075 alloy with zinc. The zinc coated aluminum 7075 alloy was fabricated using Time Dependent Electro-Plating Technique. The thickness of the coating is a function of time. The varying thickness of zinc coating was obtained based on the time estimates, which includes 10, 15 and 20 microns. Specimens were prepared according to ASTM standards, which were then tested for mechanical properties such as surface hardness, tensile strength and fracture toughness at different loading conditions. The results, when compared to the uncoated aluminum alloy showed significant improvement in Hardness (87 RHN). The hardness increased slightly compared to that of uncoated surface and showed no increase with the increase in the thickness of coating. The yield stressof zinc coated aluminum alloy increased (587.11 N/mm²) when compared to uncoated aluminum alloy 7075 - T6 (537.12 N/mm²), with an increase in brittleness. The fracture toughness test on CT specimen under plain strain condition for coated specimen showed an increase in K_IC value by 7.25 % compared to that of uncoated aluminum 7075–T6 alloy. Optical microscopy analysis shows that there is a good bonding of zinc coating on aluminum.

Abstract: Copper-Graphite composites have been prepared through powder metallurgy (P/M) method. 0 3 and 6 wt % of graphite particles have been added as the reinforcement to the Copper powder which forms the matrix and composites have been prepared. Microstructure of the newly prepared composites was analyzed using Scanning Electron Microscopy (SEM). Wear test was done using Pin-on-disc tribometer according to G99 standards. A linear regression Mathematical model has been developed using RSM to predict the sliding wear behavior of the composites. Optimization has been done using RSM and also based on ANOVA to find the significant parameters affecting the sliding wear.

Abstract: Investment casting process has been a widely used process for centuries. It is known for its ability to produce components of complex shapes with dimensional accuracy and excellent surface finish. Investment casting has been used to make manufacture weapons, jewellery and art castings during the ancient civilization and today it is used to manufacture engineering components. In Investment casting wax patterns are made by wax injection and then coating of the wax patterns are done by ceramic slurry, made with silica flour and binder. After dewaxing and firing molten metal is poured in the shell and solidified casting can be achieved. Investment casting can be cast any ferrous and non ferrous metal which is difficult in die casting. Finishing operations are negligible and very thin sections as.75mm can also be cast which is not possible in sand casting but there are many challenges in Investment casting. It is relatively slow process because preparation of ceramic shell consumes a lot of time, permeability of shell is very low which causes gas permeability. Incorporation of chills is very difficult. Among all these challenges gas porosity is main problem because of poor permeability, entrapment of gases due to complex geometry of the shell, reuse of scrap metal. In the present work porosity of the shell can be increase by addition of mixture of Camphor and needle coke. After firing of the shell camphor and needle coke will be burnt leaving pores for the escape of entrapped gases. Mechanical properties of the both shell will be compared with each other.

Abstract: The important material properties associated with laminated hybrid composites are the flexural and interlaminar shear strength (ILSS). These properties are relating the amount of bending and shear stress of a specific material will handle before individual plies fail. In this study the influence of stacking sequence on the flexural and interlaminar shear properties of the fabricated laminated hybrid composites, unidirectional carbon (UD) and bi-directional glass (BD) fabric /epoxy, has been investigated experimentally. The hybrid laminates were fabricated by hand lay-up technique with a total of 12 plies, by varying the position of carbon layers so as to obtain three different stacking sequences. The specimen preparation and the experimentations were carried out according to the ASTM standards. The result indicates by placing the carbon layers away from the neutral axis and at the neutral axis enhances the both flexural and interlaminar shear properties significantly. The failure modes of all specimens were investigated.

Abstract: This paper discuss on the optimization of process parameters for the machining of Al6061 aluminium alloy in Wire Electrical Discharge Machining (WEDM). Al6061 has a significant use in various domains like aerospace, ordnance, and automotive sectors. Wire EDM is used in the fields of Dies, Moulds Precision Manufacturing and contour cutting. The experiments have been conducted by varying four process parameters such as Peak current, T_on, T_off and Servo feed in three different levels. The important output measurable parameters like material removal rate (MRR), Surface roughness (Ra) value of the machined surface for each experimental runs has been measured. Taguchi’s L9(3⁴) Orthogonal Array was employed to carry on the experiments, that agree with arbitrarily opted distinct combinations of the mentioned process parameter. All experiments have been conducted using Electronica Sprintcut WEDM. Grey relational analysis was employed to change over the multi-objective measure into a tantamount individual objective function. Taguchi technique was used to optimize the overall grey relational grade. Verification experiments were done to validate the optimal results.

Abstract: In the present study, diffusion bonding of Cu/Cu was carried out at 750 °C for 60min under uniaxial pressureof 5-15MPa in vacuum. The joints were evaluated by Microtensile testing and Ultrasonic testing. The bond qualities were assessed by destructive testing (strength ratio) and nondestructive ultrasonic C–scan testing method.The bond quality obtained by both the methods is correlated in a view to use the C scan for regular testing. The optimum condition for obtaining the best bonding characteristics is reported. The joint obtained by diffusion bonding at 750 °C and a applied pressure of 15MPa for 60min gives the best bonding characteristics.Keywords: diffusion bonding/welding, Interface, Ultrasonic nondestructive testing.

Abstract: The Carbon-Carbon (C-C) composite materials are logical candidates for the manufacture of space crafts and other advanced structures, due to their low density values. These materials are naturally expensive, and the machining cost increases the final product’s price. The literature availability on the machining, particularly with reference to drilling operation of these materials is very rare. Hence an experimental investigation has taken to study the hole quality of this ubiquitous carbon-carbon composite material. This paper presents a comprehensive analysis about the influence of process parameters on the ovality of the carbon-Carbon composite plate, which is measured with a coordinate measuring machine. The drilling experiments were carried with two different tools like HSS and TiN coated Carbide materials on a CNC drilling machine. The Point Angle, spindle speed and feed rate were chosen as process parameters, and their impact on the quality of drilled hole was analyzed with the help of Taguchi’s orthogonal array and ANOVA-TM software. A comparison was done between the performances of drilling by these two different tools.

Abstract: This paper deals with the formability of AA 6061 sheet metal. The forming limit diagram of precipitation hardenable Al–Mg–Si alloy namely AA 6061 was evaluated for sheets rolled at two different temperature media namely room temperature and cryogenic temperature. The sheets were subjected to solutionising, rolling either in room temperature or cryogenic temperature with 50% or 75% reduction and short annealing before forming operation. The forming limit diagrams of the rolled sheets were plotted together to obtain a clear idea about their comparative formability.

Abstract: The evolution of mankind from Paleolithic Era to the current big Era Nine has also found versatile applications of various plastic polymers owing to some desirable properties like mechanical strength, poor electrical and thermal conductivities and as a result, subsequent generation of its wastes are thriving up. Basically plastic polymers are synthetic organic matter containing hydrocarbons having high potency for thermal decomposition for producing alternate fuel. Thermo-Catalytic reaction process of high-density polyethylene (H.D.P.E.) & polypropylene (P.P.) mixed waste is investigated by using fly ash-derived silica–alumina catalysts and bentonite clay powder. The aim of the work is to find the optimum parameters of the process with locally processed catalysts in terms of their degradation temperature and yield. The thermal degradation of H.D.P.E. & P.P. mixed waste in the presence of catalysts is done with pyrolytic environment in a pilot scale stainless steel reactor with the continuous rated supply of nitrogen and L.P.G. heating. The process parameters are measured with thermocouples, flow control devices. Fly ash and bentonite are synthesised in a lab scale and used as catalysts. A series of pyrolytic experiments are conducted with the synthesised catalysts and commercial catalyst Zeolite-Y Hydrogen to demonstrate the optimum operating parameters on yield of mixed waste H.D.P.E. & P.P. derived hydrocarbon oil.

Abstract: In this paper, a detailed experimental investigation was carried on the impact of the effects of tool pin and shoulder diameter in joining the Al 63400 aluminium alloy using FSW process. Flat plates of 6 mm thickness have been selected as the base material for obtaining single butt welded joints. The tool materials used for joining these base material plates are High Speed Steel (HSS) and High Chromium High Carbon Steel (HCHCr). This paper experimentally investigates and suggests the appropriate, suitable tool material & tool geometry for producing good quality welds in joining of Al 63400 alloy using FSW process.