Uniform strain hypothesis and thin-walled theory in arterial mechanics.

The authors (1987), and Chuong and Fung (1986) have shown that the strain and stress distributions in the arterial wall should be more uniform than those calculated on the basis of the conventional assumption that there is no stress over the cross-section of the arterial wall when all external force is removed (zero initial stress hypothesis). Instead of this assumption, the authors have proposed a new hypothesis that the circumferential strain uniformly distributes through the wall thickness at a physiologically normal loading, and named it 'uniform strain hypothesis'. Their results suggest the validity of the thin-walled theory in the vascular mechanics. This paper shows that if the uniform strain hypothesis is applied, the thin-walled theory can be used to accurately determine the constants included in the strain energy density function which describes the mechanical properties of the arterial wall. There were, however, significant differences in the values of the constants between the thin-walled theory and the thick-walled theory if assuming the conventional zero initial stress hypothesis.