deformations while “in service”. The circumferential line elements on the inner face of a bent
block can contract up to a certain critical stretch ratio λcr (say) before bifurcation occurs and
axial creases appear. For several models used to describe rubber, it is found that λcr= 0.56,
allowing for a 44% contraction. For models used to describe arteries it is found, somewhat
surprisingly, that the strain-stiffening effect promotes instability. For example, the models …