Optimization of Electro Discharge Machining Parameters on Mg / SiC P-Metal Matrix Composites by Response Surface Methodology
Metal Matrix Composites (MMCs) are present engineer ing materials which have more advantages when compare to conventional materials. Magnesium based MMCs among the MMCs have become an important resear ch subject because of their low density and high stren gth/weight ratio in recent years. The aim of this s tudy is to find out the most influence factors of the electro-disch arge machining (EDM) process parameters. The specim ens were used as Mg/SiCp metal matrix composites. The specim ens were prepared by the powder metallurgy techniqu es. Brass tool with diameter of 10mm was used to machin e the specimens. Experiments were conducted under d iff rent conditions of pulse on time (Ton), pulse off time ( Toff), current (I). The output responses measured w re material removal rate (MRR) and Tool wear rate (TWR). Mathem atical models are proposed for the above responses using response surface methodology (RSM). The analysis of variance (ANOVA) was carried out to study the effe ct of process parameters on process performance.
Synthesis, microstructure and properties characterization of disintegrated melt deposited Mg/SiC composites
In the present study, elemental and silicon carbide reinforced magnesium materials were synthesized using an innovative disintegrated melt deposition method followed by hot extrusion. Microstructural characterization studies revealed the presence of minimal porosity and completely recrystallized matrix in all the unreinforced and reinforced samples. In the case of reinforced magnesium samples, a fairly uniform distribution of SiC particulates and good SiC-Mg interfacial integrity was realized. The results of microhardness measurements revealed an increase in the brittleness of the SiC-Mg interfacial region with an increase in the amount of SiC particulates. Results of physical and mechanical properties characterization revealed that the increasing presence of SiC particulates led to an increase in hardness and elastic modulus, does not affect 0.2% yield strength and reduces the ultimate tensile strength, ductility, work for fracture and coefficient of thermal expansion. An attempt is made to correlate the results of physical and mechanical properties testing with that of the microstructural characterization.
Athenian Democracy at War
Classical Athens perfected direct democracy. The plays of this ancient Greek state are still staged today. These achievements are rightly revered. Less well known is the other side of this success story. Democratic Athens completely transformed warfare and became a superpower. The Athenian armed forces were unmatched in size and professionalism. This book explores the major reasons behind this military success. It shows how democracy helped the Athenians to be better soldiers. For the first time David M. Pritchard studies, together, all four branches of the armed forces. He focuses on the background of those who fought Athens' wars and on what they thought about doing so. His book reveals the common practices that Athens used right across the armed forces and shows how Athens' pro-war culture had a big impact on civilian life. The book puts the study of Athenian democracy at war on an entirely new footing.