Surface Fabrics

Abstract

In this chapter we will learn about the shape of surfaces, or more precisely of the trace of surfaces in two dimensions—the outlines of particle cross sections. We will look at these outlines in two ways: firstly as an extension or replacement of the PAROR analysis (described in the previous chapter); and secondly, we will look at surfaces in their own right, and describe the surface fabric as something distinct from the particle fabric. We will learn to think of surfaces, not in terms of ‘passive’ boundaries of three-dimensional bodies, but in terms of ‘active’ two dimensional structures whose geometry and arrangement in space have a mechanical significance. The physical processes that shape the geometry of surfaces (pressure solution, grain boundary migration, grain boundary diffusion, etc.) may be quite different and completely independent from those processes that influence the shape of particles (strain, rotation, imbrication, abrasion, comminution, etc.). One important process that affects the shape of surfaces is deformation. This will be discussed in the next chapter where we will consider surface elements from the point of view of strain analysis, and think of lines and outlines as the deformed versions of initially randomly oriented surfaces or unstrained outlines of (undeformed) particles.