What Distinguishes Brittle From Ductile Behavior?
If brittle fracture were the sole mechanism for materials failure, our world would be quite fragile. However, there are two generic types of materials failure: brittle fracture and ductile bending. In the first case, atomic bonds are broken, and such a failure is easily recognized when you see glass shatter. For ductile failure, such a catastrophic event does not occur. Tough materials like metals do not shatter; they bend because plastic deformation occurs by the motion of rows of atoms sliding passed one another on preferred slip-planes (dislocations). We briefly review some basic fundamentals of fracture mechanics. They are simple to understand even though we all know that fractured glass can look very complicated. That is because there are lots of cracks when glass shatters. As a matter of fact, micocracks are the seeds for both brittle and ductile failure. In order to understand the failure of solids, we must go to an atomic picture of matter. It is because a solid is made up of a
