主动脉弓几何参数及残余应变分布变化的实验研究

Experimental Study on the Distribution of Geometric Parameters and Residual Strains in Aortic Arch

提出了分析无载荷状态下动脉壁残余应变的弧长分析法。通过动物实验,图像测量白兔主动脉弓无载荷状态下动脉环长短半轴、平均壁厚和零应力状态下动脉弧内外边界弧长、平均壁厚等几何参数,并在此基础上,计算无载荷状态下主动脉弓周向残余应变的分布。结果表明:主动脉弓弯管段动脉壁无载荷状态几何形状近似为椭圆,而直管段近似为圆;不论在零应力状态还是在无载荷状态,动脉壁厚度均在弯管处变化较大,而直管段变化较小,同时,沿圆周方向厚度均匀;张开角沿主动脉弓的轴向分布与残余应变的轴向分布一致,在弯管段变化较大,而直管段变化较小;不论弯管段还是直管段,张开角和残余应变沿环向没有变化。

In order to quantify the residual strains in aortic arch, curve length transformation and corresponding computerized measurement of the vessel images were presented. White rabbits were used in the experiment, and the cross-sectional configuration parameters of the aortic arch, such as ellipticity, semi-major/semi-minor axis, wall thickness of the arterial wall in the non-loaded state, and inner/outer curve length, wall thickness of the arterial wall in the zero stress state, were measured. Furthermore, the circumferential residual strain distribution along the aortic arch in the zero stress state was calculated. The experimental and calculated results indicated that the aortic arch in the non-loaded state was elliptic cross-section in its bending section, but was circular cross-section in its straight section, and the whole arch was cone-shaped in axial direction, and that the opening angle or residual strain depended upon the location of the arterial arch because of the non-uniform wall thickness in axial direction in a certain extent. In the zero stress state, the absolute magnitude distributions of residual strains in internal or external walls of aortic arch were consistent well with the opening angle distribution, in which the magnitude was smaller in the straight section and larger in the bending section of the aortic arch.