  The classical flexure problem of non-linear incompressible elasticity is
revisited assuming that the bending angle suffered by the block is specified
instead of the usual applied moment. The general moment-bending angle
relationship is then obtained and is shown to be dependent on only one
non-dimensional parameter: the product of the aspect ratio of the block and the
bending angle. A Maclaurin series expansion in this parameter is then found.
The first-order term is proportional to $\mu$, the shear modulus of linear
elasticity; the second-order term is identically zero, because the moment is an
odd function of the angle; and the third-order term is proportional to
$\mu(4\beta -1)$, where $\beta$ is the non-linear shear coefficient, involving
third-order and fourth-order elasticity constants. It follows that bending
experiments provide an alternative way of estimating this coefficient, and the
results of one such experiment are presented. In passing, the coefficients of
Rivlin's expansion in exact non-linear elasticity are connected to those of
Landau in weakly (fourth-order) non-linear elasticity.
