牦牛主动脉瓣叶的流变学性质

作者研究了牦牛主动脉瓣叶的单向拉伸和应力松弛行为。发现在生理应变范围内,试件的应力应变曲线斜率在纤维方向比其垂直方向约大20倍,瓣叶对应变速率不很敏感。在分析瓣叶的松弛行为时应用了冯元桢9](1972)提出的松弛模型,根据实验结果,得到了牦牛主动脉瓣叶的归一化松弛函数。

The Rheological Properties of Yak Aortic Valve Leaflets

For the investigation valve, it isnecessary to recognize and understandthe mechanical properties of naturalheart valves. In this study, in vitro,the uniaxial tensile rheologicalproperties of yak aortic valves havebeen studied. Tissue strip spemens cut in twodirections,radial and circumferentialas shown in figure 1 wereinvestigated. The collagen fibres inthe leaflets show stiffenning effectand cause a marked anisotropy.Within the physiological range oftension, the strength of yak aorticvalve leaflet specimens in the radialdirection was about 20 times largerthan those of specimens taken alongthe perpendicular direction. Two aspects of viscoelastic beha-viour of yak aortic valve leafletswere tested: the strain rate sensitivityof the stress-strain curves andrelaxation behaviour. In analyzingthe relaxation behaviour, we usedthe relaxation model proposed byFung (1972), and obtained the con-stitution equation of yak arotic valveleaflets. About 25-30% stress relaxa-tion was found.