中文摘要：

目的研究猪胸主动脉血管各向异性的力学特性。方法收集21条猪胸主动脉血管并分成3组。沿每条血管的轴向剖开并展成平面，以展开后血管的长方向（即血管轴向）0°为起始角，逆时针方向分别切取30°、45°、60°、90°、120°、135°、150°、180。8个角度方向的样本。以1、5、10mm／min的加载速率分别对3组样本进行单轴拉伸测试，以获得血管样本在8个不同方向及3种加载速率下的弹性模量和极限应力。结果不同角度样本的应力一应变曲线呈现出不同的黏弹性行为；随着样本角度的变化，从30°开始，弹性模量逐渐增大，到90°时弹性模量最大，然后逐渐减小，直到180°；极限应力与弹性模量的变化规律基本一致。不同加载速率对弹性模量和极限应力的结果具有明显的影响，但对血管的各向异性度影响较小。结论猪主动脉血管呈现较强的各向异性，研究结果为有限元分析建模中材料属性的赋值提供参数参考，对理解血管生物力学特性具有重要的意义。

英文摘要：

Objective To study the anisotropic mechanical properties of the thoracic aorta in porcine. Methods Twenty-one porcine thoracic aortas were collected and categorized into three groups. The aortas were then cut through in their axial directions and expanded into two-dimensional planes. Then, by setting the length direction of the planar aortas （i. e., axial directions of the aortas） as 0°, each planar aorta was counterclockwisely cut into 8 samples with orientation of 30°, 45°, 60°, 90°, 120°, 135°, 150° and 180°, respectively. Finally, the uniaxial ten- sile tests were applied on three groups of samples at the loading rates of 1, 5 and 10 mm/min, respectively, to obtain the elastic modulus and ultimate stress of the aorta in different directions and at different loading rates. Results The stress-strain curves exhibited different viscoelastic behaviors. With the increase of sample orientations, the elastic modulus gradually increased from 30°, reached the maximum value at 90°, and then gradually decreased till 180°. The variation trend of ultimate stress was similar to that of elastic modulus. Moreover, different loading rates showed a significant influence on the results of elastic modulus and ultimate stress, but a weak influence on the anisotropic degree. Conclusions The porcine thoracic aorta is highly anisotropic. This research finding provides parameter references for assignment of material properties in finite element modeling, and is sig- nificant for understandina biomechanical orooerties of the arteries.