
438 
R. 
W. 
Ogden 
since the 
1940’s, 
stimulated by  the need  to describe and explain the 
mechanical behaviour 
of 
materials, such 
as 
natural rubber, which are 
capable of  undergoing large elastic deformations.  The fabrication 
of 
synthetic rubber-like  materials has provided  further stimulus, and, 
more recently, application 
of 
the theory to the study of  the mechanics 
of 
biological  tissues has been much in evidence.  The range of  appli- 
cations is growing,  a.nd nonlinear  elasticity  can  now  be regarded 
as 
very  much  an interdisciplinary  subject area, impinging on engineer- 
ing, materials science, chemistry,  physics and biology.  The inherent 
nonlinearity  of  the mathematical theory  presents  many  difficulties 
but it also offers 
a 
wealth 
of 
exciting  and challenging  opportunities 
for researchers in 
a 
diversity 
of 
fields, but notably in theoretical me- 
chanics, applied mathematics, pure mathematics, numerical  analysis 
and computational mechanics. 
In 
this  article the intention is  not  to provide 
a 
comprehensive 
account 
of 
nonlinear  elasticity  but  to concentrate 
on 
the main in- 
gredients  of  the theory and to illustrate how  the nonlinearity  influ- 
ences the nature 
of 
the solution of some very  simple boundary-value 
problems.  Different  flavours 
of 
the theory,  with  varying  degrees  of 
mathematical sophistication, are encountered 
in 
the literature, and 
the reader is referred to the texts by Truesdell and No11 
[20], 
Marsden 
a.nd Hughes 
[ll], 
Ogden 
[14] 
and Ciarlet 
[GI, 
in particular, for more 
details 
of 
the theory.  Only 
a 
limited  number of  selected  papers are 
cited  here  and in  general,  rather  than give  full  documentation, we 
point to the above-mentioned  monographs for references  to original 
sources; see also the recent  review  article by  Beatty 
[4]. 
2 
Basic Equations 
2.1 
Kinematics 
We  consider 
a 
continuous  body  which  occupies 
a 
connected  open 
subset of 
a 
three-dimensional  Euclidean  point space, and we refer to 
such 
a 
subset 
as 
a 
configuration 
of 
the body.  We identify an arbitrary 
configuration as 
a 
reference configuration 
and denote this by 
B,. 
Let 
points in 
B, 
be labelled  by  their position  vectors 
X 
relative 
to 
an