IN this monograph I have attempted to set out, in as elemen- tary a form
as possible, the basic mathematics of the theories of elasticity,
plasticity, viscosity, and rheology, together with a discussion of the
properties of the materials involved and the way in which they are
idealized to form a basis for the mathe- matical theory. There are many
mathematical text-books on these subjects, but they are largely devoted
to methods for the solution of special problems, and, while the present
book may be regarded as an introduction to these, it is also in- tended
for the large class of readers such as engineers and geologists who are
more interested in the detailed analysis of stress and strain, the
properties of some of the materials they use, criteria for flow and
fracture, and so on, and whose interest in the theory is rather in the
assumptions involved in it and the way in which they affect the
solutions than in the study of special problems. The first chapter
develops the analysis of stress and strain rather fully, giving, in
particular, an account of Mohr's repre- sentations of stress and of
finite homogeneous strain in three dimensions. In the second chapter, on
the behaviour of materials, the stress-strain relations for elasticity
(both for isotropic and simple anisotropic substances), viscosity, plas-
ticity and some of the simpler rheological models are described.