Mechanical Engineering

This paper describes the study of coefficient of thermal expansion (CTE) of as-cast and heat treated aluminium 7075 alloys. These alloys were subjected to different aging durations. The stir casting technique is used to prepare the specimens. These specimens were machined in accordance with ASTM standards followed by heat treatment process. All the specimens were aged to different periods of 1hr, 3hr, 5hr at an aging temperature of 175 oC. Coefficient of thermal expansion tests were performed in both as-cast and heat treated conditions. In each case the coefficient of thermal expansion values were found to increase with increase in aging durations. Solution heat treatment at 530 oC followed by artificial aging at 175 oC found to increase in dimension change of every specimen tested. The coefficient of thermal expansion curves exhibited some residual strains, which were decreased with the increase in aging durations.

The optimal tilt angle of solar photovoltaic panel in Ilorin, Nigeria was determined. The solar panel was first mounted at 0o to the horizontal and after ten minutes, the voltage and current generated with the corresponding atmospheric temperature were recorded. The same procedure was repeated for 2o to 30o at a succession of 2o at ten minutes time interval over the entire measurement period. The result obtained shows that the average optimal tilt angle at which a solar panel will be mounted for maximum power performance at fixed position in Ilorin is 22o. This optimum angle of tilt of the solar panel and the orientation are dependent on the month of the year and the location of the site of study.

Epoxy/Unsaturated polyester (UP) blend is prepared with varying montmorillonite (MMT) clay (viz. 0%, 1%, 2%, 3%, 4% and 5% by weight) content. The chemical resistance of these nanocomposites to some acids, alkalis and solvents is studied. The hardness property of these nanocomposites is determined. The nanocomposites showed good resistance to acids and alkalis, but showed minimal resistance to solvents. The nanocomposite blend indicated better hardness at 3% clay when compared to other combinations considered in this study. The homogeneous morphologies of the UP toughened epoxy and epoxy/UP/clay nanocomposite systems are ascertained using scanning electron microscope (SEM) and transmission electron microscope (TEM) studies. The above studies indicate that the Epoxy/UP/MMT clay nanocomposite can be used in applications like aerospace, automobiles and marine systems. The main objective of the study is to identify a low-cost, light-weight, eco-friendly and high-strength composite material that can be used for various engineering and commercial applications.

Since ages, copper and its alloys have found extensive applications in manufacture of bushes and bearings, heat transfer conductors, high conductivity electrical contactors and so on. However, currently, in all these applications, there is a significant enhancement in the service loads, wear resistance, conductivity and thus forcing the material researchers to develop a newer class of copper based advanced materials. In this direction, researchers have focused their attention on improving the strength and the tribological properties copper. The present investigation aims to evaluate the effect of deformation and heat treatment on the sliding wear and friction behavior of copper using a pin-on-disc wear testing machine, giving emphasis on the parameters such as wear rate and coefficient of friction as a function of sliding distance (0– 2000 m) at constant applied Pressure of 0.2 MPa and at a fixed sliding speed of 3.35 m/s, characterizing the deformed and heat treated copper samples in terms of microstructure, micro hardness and wear surface analysis through scanning electron microscope. The results revealed that the highly deformed copper exhibited superior wear resistance properties than the as received copper, while the coefficient of friction followed an opposite trend. Moreover, the wear rate of the copper, heat treated at above recrystallisation temperature is noted to be invariant to the sliding distance and decreased with increasing degree of deformation. Microstructure of as received copper shows fairly uniaxial grains in the matrix where as highly deformed copper shows elongated grains in the structure. The wear mechanism of the investigated materials was studied through worn surfaces examination of the developed wear tracks.

Poka yoke is a very powerful set of technique that either keeps defects from occurring or indicating immediately when a defect occurs. It relies on creativity and common sense to create low cost, effective inspection devices. Like many quality tools, mistake-proofing is not a solution for every kind of defect or quality problem. The poka yoke aims to reduce the rejection, increase the production and avoid fatigue of worker. The beauty of this lies in that anyone, from manager to line supervisor to line employee can bring this concept into service. These devices are used either to prevent the special causes that result in defects, or to inexpensively inspect each item that is produced to determine whether it is acceptable or defective. The paper contains poka yoke fundamentals to improve the production of lever cam follower and to achieve the target of zero defects over the whole process machining.

The need for flexible processes is increasing day by day. It permits rapid low cost switching from one product line to another. This is possible with flexible workers whose multiple skills would develop the ability to switch easily from one kind of task to another. As main resources, flexible processes and flexible workers would create flexible plants which can adapt to changes in real time increase in production using movable equipment, knockdown walls and easily accessible and re-routable utilities. In this paper a real time simulation is done to find out the optimum values of production and operation variables.

The aim of the present study is to investigate the optimum operating temperature of a compression ignition (CI) engine that will operate with the minimum level of exhaust emissions. The blends of jatropha with diesel in varying proportions (B10, B20 and B40) are prepared and are investigated in CI engine test rig. The result of engine emissions like CO2, CO, HC and NOx of pure diesel and biodiesel and their blends are shown by various graphical representations with respect to the engine coolant temperature at different engine loads. From the present study, it can be inferred that it is preferable to operate the engine at temperature 65?C-80?C.

The optimization of computer numerical control(CNC) boring operation parameters for aluminum alloy 6063 T6 using Taguchi and Grey Relational Analysis(GRA) optimization technique. Machining industry is playing a crucial role in the present manufacturing scenario and boring is an operation which is quite highly used nowadays to enlarge and achieve greater accuracy of the internal holes. In the present work an attempt is made to select the combination of optimum cutting parameters which results in better surface finish (minimum surface roughness i.e. Ra and Rq) and Circularity (Cr). Machining with optimum cutting parameters will result in minimum machining time and enhance the productivity. Three parameters viz. cutting speed, feed and depth of cut of boring bar has been taken as control factors. The cutting trials are performed as per Taguchi L27(3^3) orthogonal method to deal with the response from multi-variables. Taguchi orthogonal array is designed with three levels of boring parameters with the help of software Minitab 16. Grey Relational Analysis is performed for finding out the optimal parameter setting for the Al alloy 6063 T6 material. Additionally, for analyzing the data, the analysis of variance (ANOVA) technique is used to find the significant factors and their individual contribution in the response function i.e. surface roughness and Circularity.

In this paper, the composite laminates were fabricated to different weight percentage of uni-directional and stitched cross mat E-glass fibers, glass and Kevlar fiber reinforced with epoxy resins and hardener. For laminates fabrication epoxy matrix is maintained is constant weight percentage (60%) and glass fibers with different stacking sequences is added with various weight percentage. Mechanical behaviour of composites such as tensile property, flexural property & impact resistance are study in this investigation. The various geometry of E-Glass/Kevlar fiber reinforced laminates manufactured by hand lay-up method and followed by compression moulding technique. Where epoxy is constant (60%) and change the fiber percentage, specimens prepared with difference stacking sequences material are tested. The results show tensile strength and impact resistance are high to the stitched cross glass(SCM) fiber mat(40% ) .The flexural strength and natural frequency is high in order to Chopped strand (CSM) mat(10%)/Kevlar(K) fiber(30%), CSM(30%)/K(10%).

A numerical model has been formulated to simulate the capillary tube in split air conditioners of 1 and 2 TR capacities under high outdoor air temperatures. The outdoor air temperature was varied from 35 to 55°C with 5 °C increments. Three environment friendly refrigerants were used as alternatives to R22. They are R290, R407C and R410A. Finite difference method has been adopted in conjunction with EES software. This model is capable of predicting pressure, temperature, quality, velocity and viscosity distributions through the capillary tube for all refrigerants. The geometrical parameters and input conditions to the capillary tube model are extracted from experimental data. These include inner diameter, mass flow rate, surface roughness, temperature and pressure of the subcooled liquid refrigerant.The results show that the capillary choking length increases with increasing outdoor air temperature. Results of the simulation show that R290 needs more capillary length than the other refrigerants investigated, whereas R410A needs less capillary tube length.