The mechanical property of arterial walls is one of the most important factors which affect the blood circulation. Most studies related to dynamics of arterial walls to date have consists of analyzing the response in the circumferential direction of a tubular vessel rather than in the axial direction. Histological findings, however, indicate that the arterial wall has anisotropic mechanical properties. It is necessary, therefore, to analyze the mechanical properties of arterial walls in two directions, i. e. the axial and the circumferential directions. In the present study, the axial deformation behavior of arterial walls has been investigated by the tensile test.
Abdominal aortas, common carotid arteries and femoral arteries obtained from 5 mongrel dogs were stretched in the axial direction, keeping the internal pressure at various levels. Results obtained are :
1) The deformation-rate dependency of mechanical behavior was not observed in the range of 0.1 to 10.0 mm/sec.
2) Mechanical properties of arteries in the axial direction were dependent on the internal pressure applied. This pressure dependency was largest in the abdominal aorta. The maximum extensions were not affected by the internal pressure level.
3) The internal and the external radii, and the wall thickness of arterial walls decreased gradually with increasing axial tension in the lower stress range. In the higher stress stage, however, there were rapid decrease in these radii although the wall thickness remained unchanged.
4) The anisotropic mechanical behavior was observed clearly. In the lower deformation range, arterial walls were more extensible in the circumferential direction than in the axial direction, but vice versa in the higher deformation range.
5) Mechanical properties of arterial walls in the axial direction were expressed by the constitutive equations which we proposed in a previous paper (Jap. Jnl. Med. Electr. and Biol. Eng., Vol. 13, pp. 293-298 (1975)).
