Showing papers by "Saroj Kumar Mohapatra published in 2009"

Investigating and modeling tool-wear rate in the ultrasonic machining of titanium

Abstract: Titanium is known as the metal of the future because of its excellent combination of properties such as high specific strength, low thermal conductivity, and high corrosion resistance. There is a critical need for developing and establishing cost-effective methods for the machining of titanium, especially in terms of tool-wear optimization. This paper addresses the application of ultrasonic machining, an impact machining process for the cost-effective machining of commercially pure titanium (ASTM Grade-I) and evaluation of tool-wear rate under the effect of different process parameters. Tool material, abrasive material, slurry concentration, abrasive grit size, and power rating of the ultrasonic machine were included as the input factors in this investigation. The optimal settings of these parameters were determined through experiments planned, conducted, and analyzed using the Taguchi method. The significant parameters contributing most to the variation in tool-wear rate were identified and the results obtained were validated by conducting the confirmation experiments. Thereafter, the outcome of the Taguchi model has been used for developing a micro-model for tool-wear rate (TWR); using Buckingham’s pie theorem. A comparison of the experimental results obtained assists in the validation of the model.

Investigating the Machining Characteristics of Titanium Using Ultrasonic Machining

Abstract: Titanium has been known as the ‘metal of the future’ for last few decades owing to its ever increasing applications in aerospace; marine; defense; nuclear energy; missiles; chemical production; hydrocarbon processing; power generation; desalination; nuclear waste storage and processing; metal recovery; offshore; marine deep sea applications; anodes; automotive components, food and pharmaceutical processing, medical implants and surgical devices and many other emerging fields of science and technology. Titanium is branded as difficult-to-machine metal as the conventional machining processes are unable to provide cost-effective solution for its commercial machining. Titanium is machined commercially by non-traditional methods such as Electric Discharge Machining (EDM) and Laser Beam Machining (LBM), but the surface quality obtained is not satisfactory from the prospect of surface integrity as well as surface finish. Ultrasonic Machining (USM) is another non-traditional machining process that is widely used in commercial machining of hard and brittle materials such as ceramics, refractory materials and precision stones. USM is a process known for its capabilities in providing excellent surface finish without any significant alterations is surface integrity or structure of the work material. Moreover, the compressive stress induced in the sub-surface as a result of repeated impacts of abrasive grains contributes in improving the fatigue strength of the machined components; which is a very important aspect especially for a material like titanium. Hence, the study was aimed to investigate the machining characteristics of titanium using different tool materials in ultrasonic machining and to model these characteristics for their application in the concerned manufacturing industry. The machining characteristics investigated are material removal rate (MRR); tool wear rate (TWR) and surface roughness. In the present investigation, the work has been limited to commercially pure titanium (ASTM Grade-I) as work material, in combination with five different tool materials (High carbon steel; High speed steel; titanium; titanium alloy and cemented carbide) for experimentation. The results showed that the response variables were strongly influenced by control factors (input parameters).

CFD Analysis of Bubbling Fluidized Bed Using Rice Husk

Abstract: Rice is Cultivated in all the main regions of world. The worldwide annual rice production could be 666million tons (www.monstersandcritics.com,2008) for year 2008. The annual production of rice husk is 133.2 million tons considering rice husk being 20% of total paddy production. The average annual energy potential is 1.998 *1012 MJ of rice husk considering 15MJ/kg of rice husk. India has vast resource of rice husk; a renewable source of fuel, which if used effectively would reduce the rate of depletion of fossil energy resources. As a result a new thrust on research and development in boilers bases on rice husk is given to commercialize the concept. CFD is the analysis of systems involving fluid flow, heat transfer and associated phenomena such as chemical reactions by means of computer-based simulation. High quality Computational Fluid dynamics (CFD) is an effective engineering tool for Power Engineering Industry. It can determine detailed flow distributions, temperatures, and pollutant concentrations with excellent accuracy, and without excessive effort by the software user. In the other words it is the science of predicting fluid flow, heat and mass transfer, chemical reactions and related phenomena; and an innovate strategy to conform to regulations and yet stay ahead in today’s competitive power market. This paper is divided into two parts; in first part review of CFD applied to the various types of boilers based on biomass fuels/alternative fuels is presented. In second part CFD analysis of fluidized bed boilers based on rice husk considering the rice husk based furnace has been discussed. The eulerian multiphase model has used for fluidized bed. Fluidized bed has been modeled using Fluent 6.2 commercial code. The effect of numerical influence of bed superheater tubes has also been discussed.

Effect of Flow Arrangements on Thermohydraulic Performance of a Microchannel Heat Sink

Abstract: The advancements in fabricating and utilizing microchannel heat sinks (MCHS) for cooling of electronic devices during the last decade has not been matched by corresponding advances in our fundamental understanding of the unconventional micro fluidics Many theoretical and experimental studies have been reported for the heat transfer analysis along the direction of flow within the microchannels, but to the best knowledge of the authors, the effect of the size of the inlet and outlet plenum and direction of the flow to the plenums was not studied exhaustively till date The liquid is supplied to the microchannels via the inlet and outlet plenums and this can be achieved by many flow arrangements Due to the small size of the channel dimensions, the entrance and exit conditions will significantly affect the heat transfer characteristics of the flow field in the channel Instability effects at the entrance and exit regions of the micro-channel also need to be fully understood for efficient design of microchannel heat sinks This paper presents an experimental study that has been conducted to explore the effect of entrance & exit conditions of the liquid flow within a copper micro-channel heat sink (MCHS) Three test pieces having inlet & outlet plenum dimensions of 8mm × 30mm, 10mm × 30 mm and 12 mm × 30 mm each with constant depth of 25 mm have been selected Three different flow arrangements (U-Type, S-type and P-type) are studied for each test piece resulting in total nine flow arrangements Each micro-channel heat sink contains an array of micro-channels in parallel having individual width of 330μm and channel depth of 25 mm A comparison is made based on thermohydraulic performance of MCHS for different flow conditions at inlet and outlet plenums maintaining constant heat flux Deionised water has been used in the experiments for the Reynolds number ranging from approximately 220 to 1100 The results are interpreted based on pressure drops and maximum temperature variations for these nine flow arrangements Tests has been conducted to look for optimized dimensions and flow conditions at inlet and outlet plenums for the given fixed length of microchannels under same conjugate heat transfer conditions Evaluations of experimental uncertainties have been meticulously made while selecting the instruments used in the experimental facilityCopyright © 2009 by ASME