  We study the peculiar wrinkling pattern of an elastic plate stamped into a
spherical mold. We show that the wavelength of the wrinkles decreases with
their amplitude, but reaches a maximum when the amplitude is of the order of
the thickness of the plate. The force required for compressing the wrinkled
plate presents a maximum independent of the thickness. A model is derived and
verified experimentally for a simple one-dimensional case. This model is
extended to the initial situation through an effective Young modulus
representing the mechanical behavior of wrinkled state. The theoretical
predictions are shown to be in good agreement with the experiments. This
approach provides a complement to the "tension field theory" developed for
wrinkles with unconstrained amplitude.
