An accurate characterization of soft biological tissue properties is essential for a realistic simulation of surgical procedures. Unconfined uniaxial compression tests with specimens affixed to the fixtures are often performed to characterize the stress-stretch curves of soft biological tissues, with which the material parameters can be obtained. However, the constrained boundary condition causes non-uniform deformation during the uniaxial test, posing challenges for accurate measurement of tissue deformation. In this study, we measured the deformation locally at the middle of liver specimens and obtained the corresponding stress-stretch curves. Since the effect of the constrained boundary condition on the local deformation of specimen is minimized, the stress-stretch curves are thus more realistic. Subsequently, we fitted the experimental stress-stretch curves with several constitutive models and found that the first-order Ogden hyperelastic material model was most suitable for characterizing the mechanical properties of porcine liver tissues. To further verify the characterized material properties, we carried out indentation tests on porcine liver specimens and compared the experimental data with computational results by using finite element simulations. A good agreement was achieved. Finally, we constructed computational models of liver tissue with a tumor and investigated the effect of the tumor on the mechanical response of the tissue under indentation. The computational results revealed that the liver specimen with tumor shows a stiffer response if the distance between the tumor and the indenter is small.

中文翻译：

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用于计算模拟癌组织压痕的猪肝脏特性的机械特性。

软生物组织特性的准确表征对于外科手术的真实模拟至关重要。通常进行无侧限单轴压缩试验，将试样固定在固定装置上，以表征软生物组织的应力-拉伸曲线，由此可以获得材料参数。然而，约束边界条件在单轴测试过程中会导致非均匀变形，对准确测量组织变形提出了挑战。在本研究中，我们测量了肝脏标本中间局部的变形，并获得了相应的应力-拉伸曲线。由于约束边界条件对试样局部变形的影响被最小化，因此应力-拉伸曲线更加真实。随后，我们将实验应力-拉伸曲线与几个本构模型拟合，发现一阶 Ogden 超弹性材料模型最适合表征猪肝组织的力学特性。为了进一步验证表征的材料特性，我们对猪肝标本进行了压痕测试，并通过使用有限元模拟将实验数据与计算结果进行了比较。达成了很好的协议。最后，我们构建了具有肿瘤的肝组织的计算模型，并研究了肿瘤对压痕下组织机械响应的影响。计算结果表明，如果肿瘤与压头之间的距离较小，则带有肿瘤的肝脏标本表现出更强烈的反应。