  One of the least studied universal deformations of incompressible nonlinear
elasticity, namely the straightening of a sector of a circular cylinder into a
rectangular block, is revisited here and, in particular, issues of existence
and stability are addressed. Particular attention is paid to the system of
forces required to sustain the large static deformation, including by the
application of end couples. The influence of geometric parameters and
constitutive models on the appearance of wrinkles on the compressed face of the
block is also studied. Different numerical methods for solving the incremental
stability problem are compared and it is found that the impedance matrix
method, based on the resolution of a matrix Riccati differential equation, is
the more precise.
