Abstract

In the present work, the feasibility studies for drilling of metals through microwave irradiation have been carried out. The trial experiments for drilling on aluminium, copper and stainless steel specimens of thickness 1 mm were carried out in domestic microwave oven of frequency 2.45 GHz at power 900 W. The bulk metallic materials reflect microwave radiations owing to low skin depth (few microns) at room temperature which makes it extremely difficult to achieve heating in bulk metals using microwaves. The heating of selective area of targeted metallic materials have been achieved by microwave hybrid heating technique by using suitable susceptor material. The susceptor readily couples with microwave and gets heated up rapidly which, in turn, elevates the temperature of target area of the bulk metallic sheet. At elevated temperature, the metallic sheet is deformed plastically by a drill bit of tungsten material through spring action. Consequently, the force required to create deformation has been reduced. Results of the initial trials have been discussed in the paper.

Abstract

Friction Stir Welding (FSW) has several benefits in welding “difficult to weld” aluminium alloys and dissimilar materials. FSW requires careful selection of process parameters (mainly the tool geometry, tool rotational speed, welding speed and the axial downward force) in order to make a defect free weld joint. The tool geometry is the most influential aspect of process development. It plays a vital role in material flow towards joint consolidation, as the weld microstructure varies with the tool pin design.  The paper attempts to establish the pin profile geometry that develops low stress in the tool and weld joint and thereby simultaneously enhancing the plastic flow of the metal to maximize the weld strength by forming a superior Inter Metallic Compound (IMC) in the weld zone. FSW tools with various pin profiles are designed based on theories of failures. Modeling and computational analysis were performed on the basic profiles pf the pin geometry. Results indicate that the resistance force exerted by the cylindrical shape pin profile is high and the stress induced is less in the weld joint as compared to other type of profiles. Experimental analysis performed on AA7075 alloys reveals that maximum weld strength and sound metallurgical properties is observed in the joint produced by the cylindrical pin under optimum weld conditions due to uniform material flow throughout the weld cross section.

Abstract

A global optimization algorithm based on plant growth is used to perform the dimensional synthesis of a slider-crank mechanism. The PGO is based on the plant growth characteristics in which an artificial plant growth model is built including leaf growth, branching, phototropism, and spatial occupancy. The plant growth process is that a plant grows a trunk from its root; some branches will grow from the nodes on the trunk; and then some new branches will grow from the nodes on the branches. Such process is repeated, until a plant is formed. This process is simulated in this algorithm by producing new points (branch points) from initial points (roots). After producing the new points (branch points), the algorithm searches the optimum solution around these points through the operation called leaf growth (for local search). This is used to improve the accuracy of the solution.

In this algorithm, Nelder-Mead Simplex method is used for local search for a case. For the synthesis of Slider-crank mechanism, pattern search method is used as the local search method. Initially the PGO is applied to a test function and the results are in good agreement to the analytical solution. Then it is applied to the slider-crank mechanism to perform the dimensional synthesis such that for a given set of crank angles, the slider occupies specified positions. The results obtained here are in agreement with the results obtained from the other synthesis procedures described in the literature. It is concluded that the PGO algorithm presented here can be applied to solve such problems.

Abstract

Shrinkage characteristic of US A356 cast aluminium alloy has been discussed in the present study. The reduction in specific volume leads to shrinkage in castings and it can be visualized as a casting defect. The shrinkage characteristic has been studied using finite difference based casting process simulation software and it is quantified using mathematical formulae. CAD has been used for construction of three dimensional model of the shrinkage defect. Shrinkage characteristic has also been quantified through experimental validation studies and compared well with casting process simulation. Shrinkage characteristic study and control is essential for producing defect free castings. Influence of casting shape on the shrinkage characteristic has been studied in this paper.

Abstract

An assembly line is a sequence of work stations connected together by material handling. Goal of assembly line balancing is to minimize work stations, minimize work load variance and to minimize idle time. This paper aimed to minimize work load and machine idle time. Bottleneck problem of continuous flow type horn assembly line is eliminated by ECRS (Eliminate, Combine, Rearrange and Simplify) principles. Improvement of production rate and balance loss ratio of the manual assembly line is to be achieved. Verification of proposed system can be prepared by means of time values calculated from MODular Arrangement of Predetermined Time Standards (MODAPTS) method. The result shows that Bottleneck time reduced from 23.04 to 16.65 seconds and Production rate increased from 156 to 216 pieces per hour.

Abstract

Aluminium metal matrix composites reinforced with  SiC and B4C  particles are a unique class of advanced engineered materials that have been developed  to use in high strength , high wear resistant and tribological applications. The conventional techniques of producing these composites have some drawbacks. In this study, the aluminium hybrid composite is fabricated using stir casting method.  15 % by weight of SiC particles with an average size of 20 µm along with 5 % by weight of B4C particulates were reinforced in to the molten aluminium alloy of designation A356. The hardness, chemical composition and the micro-structure of the hybrid composite were investigated. Homogeneous distribution of SiC and B4C within Al hybrid composites is clear from the SEM images.  Finally an attempt to study the machinability   characteristics of the hybrid MMC in turning using Poly crystalline Diamond inserts (PCD) of Grade 1500.The experiment was conducted in a medium duty lathe of spindle power 2kW at various cutting speeds, feeds and depths of cut and parameters such as Power consumed, surface roughness were measured.  The surface finish observed was found to be very close to the theoretical surface finish. The deviation in the value is concluded as the other parameters which influencing the machining. The optimum cutting conditions were obtained from the analysis of the results. By using this optimum cutting condition tool wear study was carried out. It is concluded that, tool wear mechanism is purely abrasive in nature. Surface finish is strongly dependent on cutting speed. Cutting speed is inversely proportional to surface roughness. Confirmation experiment also shows good agreement with the prediction value.

Abstract

Partially and fully sunken effect on slab-on- grade structures are reported, using silica sand as a simulating media in thermal simulation method for estimating the ground losses. The method has been used to determine the shape factor; which can be used to evaluate the heat loss to the ground for slab-on- grade.  The accuracy of the method has been evaluated by comparing the experimental result obtained for a sphere with the corresponding analytical results.