Category: Science & Engineering

Phase: A phase may be defined as a homogeneous portion of a system that has uniform physical and chemical characteristics. Every pure material is considered to be a phase; If more than one phase is present in a given system, each will have its own distinct properties, and a boundary separating the phases will exist across which there will be a discontinuous and abrupt change in physical and/or chemical characteristics. When two phases are present in a system, it is not necessary that there be a difference in both physical and chemical properties; a disparity in one or the other […]

Griffith’s theory Griffith’s theory of failure is based on the assumption that the low order of tensile strength in common materials is due to the presence of small cracks or flaws. Actual stresses may occur around these flaws, which are of the order of magnitude of molecular cohesion values, while the average tensile strength may be quite low. Mohr’s theory predicts that failure of materials is due to failure in shear, whereas Griffith’s theory postulates that it is due to failure at crack tips. – http://www.maden.hacettepe.edu.tr/dmmrt/dmmrt522.html Links Ductile & Brittle Fracture – http://nhml.com/resources_NHML_Ductile-Brittle-Fracture.php

Definitions: Ceramics are known for their high temperature melting points, high mechanical strengths, electrical, magnetic, optical and thermal properties. – http://www.mse.uiuc.edu/home/introduction.html The word ceramic is derived from the Greek word κεραμικός (keramikos). The term covers inorganic non-metallic materials which are formed by the action of heat. – http://en.wikipedia.org/wiki/Ceramic The percentage ionic character: of a bond between elements A and B (A being the most electronegative) may be approximated by the expression % ionic character = {1 – exp[-(0.25)(XA – XB)2]} x 100 where XA and XB are the electronegativities for the respective elements. Two characteristics of the component ions in […]