OpenCMISS/cm — pull request #194 by adamreeve (2014-10-22 07:41:28+00:00)
Title: Fix Holzapfel-Ogden (2009) constitutive relation to match paper

I4 based terms should only be included when I4 > 1, as fibres buckle and contribute no stiffness in compression.

This is stated in the paper but isn't actually made explicit in the published equation.