Mechanical thrombectomy has become the standard treatment for patients with an acute ischemic stroke. In this approach, to remove blood clots, mechanical force is applied using thrombectomy devices, in which the interaction between the clot and the device could significantly affect the clot retrieval performance. It is expected that the finite element method (FEM) could visualize the mechanical interaction by the visualization of the stress transmission from the device to the clot. This research was aimed at verifying the constitutive theory by implementing FEM based on the visco-hyperelastic theory, using a three-dimensional clot model. We used the visco-hyperelastic FEM to reproduce the mechanical behavior of blood clots, as observed in experiments. This study is focused on the mechanical responses of clots under tensile loading and unloading because in mechanical thrombectomy, elongation is assumed to occur locally on the clots during the retrieval process. Several types of cylindrical clots were created by changing the fibrinogen dose. Tensile testing revealed that the stiffness (E_0.45-value) of clots with fibrinogen could be more than three times higher than that of clots without fibrinogen. It was also found that the stiffness was not proportional to the fibrinogen dose. By fitting to the theoretical curve, it was revealed that the Mooney-Rivlin model could reproduce the hyperelastic characteristics of clots well. From the stress-relaxation data, the three-chain Maxwell model could accurately fit the experimental viscoelastic data. FEM, taking the theoretical models into account, was then carried out, and the results matched well with the experimental visco-hyperelastic characteristics of clots under tensile load, reproducing the mechanical hysteresis during unloading, the stress dependence on the strain rate, and the time-dependent stress decrease in the stress-relaxation test.

机械取栓已成为急性缺血性卒中患者的标准治疗方法。在这种方法中，为了去除血凝块，使用血栓切除装置施加机械力，其中凝块和装置之间的相互作用会显着影响凝块取出性能。预计有限元方法 (FEM) 可以通过可视化从设备到凝块的应力传递来可视化机械相互作用。本研究旨在通过使用三维凝块模型实施基于粘超弹性理论的 FEM 来验证本构理论。正如在实验中观察到的，我们使用粘超弹性有限元法来重现血凝块的机械行为。这项研究的重点是在拉伸加载和卸载下凝块的机械反应，因为在机械血栓切除术中，假定在取回过程中凝块局部发生伸长。通过改变纤维蛋白原剂量产生了几种类型的圆柱形凝块。拉伸试验表明刚度（E_{含纤维蛋白原的凝块的0.45}值）可能比不含纤维蛋白原的凝块高出三倍以上。还发现硬度与纤维蛋白原剂量不成比例。通过对理论曲线的拟合，揭示了Mooney-Rivlin模型可以很好地再现凝块的超弹性特征。从应力松弛数据来看，三链麦克斯韦模型可以准确拟合实验粘弹性数据。然后进行有限元分析，考虑到理论模型，结果与拉伸载荷下凝块的实验粘超弹性特性很好地匹配，再现了卸载过程中的机械滞后、应力对应变速率的依赖性以及时间应力松弛试验中的依赖应力降低。