OS07W0160 Residual stress and strain in the artery wall : From macroscopic to microscopic viewpoint

Abstract

The opened-up configuration of the artery wall has long been assumed to be stress-free. This is not true in a microscopic level: The aortic media has a layered structure called lamellar unit which is a pair of elastic lamina (EL) and a smooth muscle-rich layer (SML), and the EL has been reported to be stiffer than the SML. If the circumferential stress in the in vivo condition is the same between the two layers, residual stress of each layer should be different because the stress-strain relationships differ. Such residual stress is not released fully by radial cutting, but is released in the area close to the cut surface, causing hills and valleys on the surface due to residual stresses. To check this hypothesis, we have developed a scanning micro indentation tester, and measured the topography and the stiffness distribution of the cut surface. The surface of the porcine thoracic aortas has stiff hills and soft valleys as speculated. Residual stress and strain estimated from the topography and stiffness distribution were almost comparable to those estimated in the ring-like segments in no load condition. Fairly large stress may still reside in the opened-up aortic wall.