Chapter 2 - Fracture Mechanics and Friction: Muscles, Impact and New Surfaces

Abstract

This chapter covers the basics of stress analysis, fracture mechanics, and ideas on friction and discusses how muscles function, since the force and work necessary for cutting are often supplied by hand or foot when animals attack prey and afterwards chew food in the mouth. In order to determine the mechanical (strength) properties of materials, a body may be deformed by applying known loads to it, for example by hanging on weights to the suspended body. Deformation may be pulling, compressing, twisting, and bending, including combinations of the different ways of loading. The resulting deformations, extension in tension, reduction in height in compression, angle of twist, and rotation in bending, can be measured. Load–deformation behavior depends upon the temperature and the rate at which loading takes place; it also depends upon the environment, water particularly affecting the behavior of biological materials. Notch sensitivity concerns by how much the load-bearing capacity of a body containing a crack or notch is reduced compared with the uncracked body. Employment of fracture mechanics requires knowledge of the crack size. When no crack is obvious, in brittle solids the effective starter crack is related to microstructural features.