Stress

Abstract

In continuum mechanics, an element of a whole body has a mass (dm: the differential mass) and a volume (dV: the differential volume) as well as a shape. The shape is typically considered to be a hexahedron whose six surfaces are aligned with the coordinate system as shown in Fig. 8.1. The coordinate system in this whole book is the rectangular Cartesian coordinate system, which is denoted as x-y-z or 1-2-3 (for the indicial notation), with unit base vectors, ${\mathbf{e}}_{x} ( = {\mathbf{e}}_{1} )$, ${\mathbf{e}}_{y} ( = {\mathbf{e}}_{2} )$ and ${\mathbf{e}}_{z} ( = {\mathbf{e}}_{3} )$.