Role of Heat Transfer on Process Characteristics During Electrical Discharge Machining

This book comprises heat transfer fundamental concepts and modes (specifically conduction, convection and radiation), bioheat, entransy theory development, micro heat transfer, high temperature applications, turbulent shear flows, mass transfer, heat pipes, design optimization, medical therapies, fiber-optics, heat transfer in surfactant solutions, landmine detection, heat exchangers, radiant floor, packed bed thermal storage systems, inverse space marching method, heat transfer in short slot ducts, freezing an drying mechanisms, variable property effects in heat transfer, heat transfer in electronics and process industries, fission-track thermochronology, combustion, heat transfer in liquid metal flows, human comfort in underground mining, heat transfer on electrical discharge machining and mixing convection. The experimental and theoretical investigations, assessment and enhancement techniques illustrated here aspire to be useful for many researchers, scientists, engineers and graduate students

Application of Silicon Carbide in Abrasive Water Jet Machining

Silicon carbide (SiC) is a compound consisting of silicon and carbon. It is also known as carborundum. SiC is used as an abrasive material after it was mass produced in 1893. The credit of mass production of SiC goes to Edward Goodrich Acheson. Now SiC is used not only as an abrasive, but it is also extensively used in making cutting tools, structural material, automotive parts, electrical systems, nuclear fuel parts, jewelries, etc. AWJM is a well-established non-traditional machining technique used for cutting difficult-to machine materials. Nowadays, this process is being widely used for machining of hard materials like ceramics, ceramic composites, fiber-reinforced composites and titanium alloys where conventional machining fails to machine economically. The fact is that in AWJM no heat is developed and it has important implications where heat-affected zones are to be avoided. AWJM can cut everything what traditional machining can cut, as well as what traditional machining cannot cut such as too hard material (e.g. carbides), too soft material (e.g. rubber) and brittle material (e.g. glass, ceramics, etc.). The basic cutting tool used in water jet machining is highly pressurized water that is passed through a very small orifice, producing a very powerful tool that can cut almost any material. Depending on the materials, thickness of cut can range up to 25 mm and higher (Kalpakjian & Schmid, 2010). A water jet system consists of three components which are the water preparation system, pressure generation system and the cutting head and motion system

Development of Powder Metallurgy (PM) compacted Cu-TaC electrodes for EDM

The main aim of this paper is to investigate the properties of Cu-TaC electrodes produced by Powder Metallurgy (PM) method. The design of Experiment (DOE) method was used to plan the investigation. Two different compositions of the powders (Cu-TaC with 30 and 55 % wt TaC) were used. The major properties which determine suitability of electrodes for Electro Discharge Machining (EDM) are electrical conductivity, thermal conductivity and to some extent density. These properties were measured for the green compacted electrodes, analyzed and compared with their sintered counterparts. This is the initial stage to determine the suitability or otherwise of the compacted electrodes. The results showed that the compacted electrodes in green form can be suitable for EDM, since the electrical conductivities are very high (94.96-189.92�-1m-1). The thermal conductivity is good (29.70-33.20W/ m K). The density ranges between 6.13 and 9.80 g/cm3. The sintered electrodes were found to be unsuitable at the specified conditions, because they became non-conductive electrically after sintering. Current efforts are geared towards improving these properties for the sintered ones and also determining their optimum levels

A study of electrode shape configuration on the performance of die sinking EDM

This paper discusses the performance of die sinking EDM due to the shape configuration of the electrode. The effect of electrode shape on material removal rate (MRR), electrode wear rate (EWR), wear ratio (WR), and average surface roughness (Ra) has been investigated for mild steel work material and copper electrode. The shapes of the electrodes were round, square, triangular, and diamond of constant cross-sectional area of 64 mm2. Experiments were repeated for three current values of 2.5, 3.5, and 6.5 A. The highest MRR was found for round electrodes followed by square, triangular and diamond shaped electrodes. However, the highest EWR and WR were found for the diamond shaped electrodes. The minimum surface roughness was found for the round electrodes followed by square, triangular and diamond shaped electrodes. However, the influence of the shape of the electrodes on surface roughness was found to be insignificant

A new approach of applying cryogenic coolant in turning AISI 304 stainless steel

In the present study a special device has been designed to apply liquid nitrogen coolant during turning of AISI 304 stainless steel. The base of the device is a magnet and it can be fixed at any suitable position on the tool or tool post. A long flexible and adjustable copper nozzle is used to apply liquid nitrogen at any angle or from any position. Experiments with three positions of the copper nozzle were performed. The results of the investigations showed that the most effective way to apply liquid nitrogen directly to the machining zone without any interference by the chips. Tool life increased four times compared to dry machining under this condition. The next effective way was to apply liquid nitrogen along the principal cutting edge. It was found that application of liquid nitrogen coolant did not improve job surface finish, but all the three positions of the copper nozzle demonstrated almost similar effectiveness

Deterrence in Indo-Pak Context: A Critical Appraisal

It was an imbalance in the conventional power that forced Pakistan to see nuclear weapons' capability, as a deterrence against India, after the war of 1971 that resulted in separation of former East Pakistan. This is the context of ‘deterrence’ in today's South Asia. The only solution to the dilemmas created by the region's nuclearization is to engage seriously and constructively to build a better understanding of each other's conventional and nuclear policies, doctrines, and postures, and meaningful CBMs both in nuclear and conventional military spheres to build trust and confidence. Both India and Pakistan have to maintain rational decision-making to ensure the credibility of their deterrence and to achieve the objective of maintaining stability

Radial forearm free flap: A dynamic flap for single-staged multiple subunit reconstruction

We report the case of a middle aged patient with biopsy proven squamous cell carcinoma of buccal mucosa who presented to us in Aga Khan University Hospital Karachi in April, 2017 and required reconstruction of buccal mucosa, upper lip and lower lip. As per protocol of our institute the lesion was excised by the head and neck surgeon and the defect was reconstructed by our team. The defect was large comprising of buccal mucosa including the left oral commissure, upper lip and the lower lip. It was reconstructed via a free flap and a radial forearm free flap. A specially designed radial forearm free flap was harvested and used for reconstruction which resulted in a good aesthetic and functional outcome

Improving micro-hardness of stainless steel through powder-mixed electrical discharge machining

Powder-mixed electrical discharge machining (PMEDM) is the technique of using dielectric fluid mixed with various types of powders to improve the machined surface output. The process is fast gaining prominence in electrical discharge machining (EDM) industry. The objective of this investigation is to determine the ability of tantalum carbide (TaC) powder-mixed dielectric fluid to enhance the surface properties of stainless steel material during EDM. The properties of investigated are the micro-hardness and corrosion characteristics of the EDMed surface. Machining was conducted with 25.0g/L concentration of TaC powder in kerosene dielectric fluid. The machining variables used were the peak current, pulse on time and pulse off time. The effects of variables on the micro-hardness of the EDMed surface were determined. Corrosion tests were also conducted on the samples that exhibited higher hardness. Results showed that the EDMed surface was alloyed with elements from the TaC powder. The micro-hardness obtained with PMEDM is about 1,200Hv. This is about 1.5 times obtained without TaC powder in the dielectric fluid. The loss in weight during corrosion test was found to be 0.056 ug/min for PMEDM which was lower than the lowest value of 10.56 ug/min obtained for the EDM without powder dielectric fluid