目的    腹主动脉力学异常是腹主动脉瘤病变关键机制。本研究开展多比例双轴拉伸，明确血管轴向、周向力学响应规律，验证多凸多项式超弹性本构模型适用性。 方法    采集五指山猪健康腹主动脉，完成 1:1、1:3、3:1 平面双轴拉伸；采用多凸不变量四纤维模型拟合数据，非线性最小二乘标定材料参数，以R2评判拟合精度。  结果    腹主动脉呈明显非线性各向异性；等双轴拉伸下周向刚度大于轴向，非对称加载时高应变方向应力提升显著。整体平均决定系数R²高达0.9457，非对称加载下最高R2=0.9871。  结论    该多凸本构模型可精准描述腹主动脉复杂多轴力学行为，为血管生物力学仿真、有限元分析及介入器械优化提供实验与理论依据。

Objective    In this study, multi-ratio biaxial tensile tests are conducted on abdominal aortic specimens, aiming to systematically clarify the mechanical response rules of blood vessels in axial and circumferential directions, and verify the applicability of the polyconvex polynomial hyperelastic constitutive model for arterial tissue.   Methods   Healthy abdominal aortic specimens collected from Wuzhishan pigs were taken as research objects, which were commonly adopted in cardiovascular biomechanical studies due to their high similarity to human vascular anatomy and physiology. Planar biaxial tensile tests were carried out under three stretch ratios of 1:1, 1:3 and 3:1 to obtain complete mechanical response data under multi-axial loading conditions. A four-fiber hyperelastic constitutive model based on polyconvex invariants was adopted to fit the experimental stress-stretch data from each loading case. The nonlinear least squares method was used to calibrate the material parameters of the model, and the coefficient of determination R2 was employed as the index to quantitatively evaluate the fitting accuracy.   Results   Experimental results shown that the abdominal aorta presented obvious nonlinear anisotropic hyperelastic characteristics. Under equibiaxial tensile loading, the circumferential stiffness of the vessel wall was significantly higher than the axial stiffness, presenting a distinct directional difference in load-bearing capacity. Under asymmetric loading conditions, the stress response in the high-strain direction significantly enhanced, and the tangent stiffness risen remarkably with the increase of stretch degree. The overall average coefficient of determination R2 reached as high as 0.9457, reflecting favorable global fitting performance. Especially under asymmetric loading, the model achieved higher fitting accuracy, with the maximum R2 up to 0.9871.   Conclusions   The polyconvex constitutive model can accurately describe the complex multi-axial mechanical behavior of abdominal aorta under various loading conditions, and possesses good numerical stability and predictive ability. This study provides reliable experimental data and theoretical support for vascular biomechanical simulation, finite element analysis and structural optimization of interventional devices, and also offers a mechanical reference for further research on the pathological mechanism of vascular diseases.