A more Accurate description of the mechanical behavior of brain tissue could improve the results of computational models. While most studies have assumed brain tissue as an incompressible material with constant Poisson’s ratio of almost 0.5 and constructed their modeling approach according to this assumption, the relationship between this ratio and levels of applied strains has not yet been studied. Since the mechanical response of the tissue is highly sensitive to the value of Poisson’s ratio, this study was designed to investigate the characteristics of the Poisson’s ratio of brain tissue at different levels of applied strains. Samples were extracted from bovine brain tissue and tested under unconfined compression at strain values of 5%, 10%, and 30%. Using an image processing method, the axial and transverse strains were measured over a 60-s period to calculate the Poisson’s ratio for each sample. The results of this study showed that the Poisson’s ratio of brain tissue at strain levels of 5% and 10% was close to 0.5, and assuming brain tissue as an incompressible material is a valid assumption at these levels of strain. For samples under 30% compression, this ratio was higher than 0.5, which could suggest that under strains higher than the brain injury threshold (approximately 18%), tissue integrity was impaired. Based on these observations, it could be concluded that for strain levels higher than the injury threshold, brain tissue could not be assumed as an incompressible material, and new material models need to be proposed to predict the material behavior of the tissue. In addition, the results showed that brain tissue under unconfined compression uniformly stretched in the transverse direction, and the bulging in the samples is negligible.

更准确地描述脑组织的机械行为可以改善计算模型的结果。虽然大多数研究都假设脑组织是一种不可压缩的材料，其恒定泊松比几乎为 0.5，并根据这一假设构建了他们的建模方法，但尚未研究该比率与应用应变水平之间的关系。由于组织的机械响应对泊松比值高度敏感，本研究旨在研究不同施加应变水平下脑组织泊松比的特征。从牛脑组织中提取样品并在无侧限压缩下以 5%、10% 和 30% 的应变值进行测试。使用图像处理方法，在 60 秒内测量轴向和横向应变，以计算每个样品的泊松比。这项研究的结果表明，脑组织在 5% 和 10% 应变水平下的泊松比接近 0.5，并且假设脑组织是不可压缩材料是在这些应变水平下的有效假设。对于 30% 压缩下的样本，该比率高于 0.5，这可能表明在高于脑损伤阈值（约 18%）的应变下，组织完整性受损。基于这些观察，可以得出结论，对于高于损伤阈值的应变水平，脑组织不能被假定为不可压缩材料，需要提出新的材料模型来预测组织的材料行为。此外，