hard britte solids. Why are ceramics strong and hard? Well, most ceramics have ionic or valent bonding. These bonds themselves are strong. So, they are hard and strong by virtue of the strong bond strength that prevails in them. But then you may ask: if they hard and strong. how come they are are brittle? Well, they are brittle because they do not have the ability to plas tically deform and adapt to the extra strain generated due to the applied stress! Then the question is: Why cant they deform plastically like metals at room temperature? The problem with ceramics is that--unless exposed to a state of hydrostatic stress within a small confined volume-ceramic very at room temperature generally do not have five independent slip or more systems actively operative. That is what is required to satisfy the von Mise criterion of plastic deformability. As the ceramies fail to satisfy this crit rion in general, they do not show any appreciable plasticity at room tem perature, so they remain unable to absorb the strain in the structure. Up continued application of stress from the external system, the accumulated strain becomes high enough to cross the failure strain limit. When that hap pens, catastrophic failure occurs, especially so in classical br solids, like glass and ceramics. Widespread practical exploitation of the brit solids like glass and ceramics is therefore somewhat limited due to the presence flaws that are either intrinsic or are induced by nanoscale, mi or macroscale contact damage. These contact-induced flaws can act as a pre- cursor to macroscopic defects. Therefore, it is essential to understand the nature and mechanism of contact-induced deforma
Posted on: Fri, 02 Jan 2015 22:28:32 +0000
Trending Topics
Recently Viewed Topics
© 2015