Farrell M D, Riches P E
J Biomech Eng. 2013 Oct;135(10):104501. doi: 10.1115/1.4025180.
Existing experimental data on the Poisson's ratio of nucleus pulposus (NP) tissue is limited. This study aims to determine whether the Poisson's ratio of NP tissue is strain-dependent, strain-rate-dependent, or varies with axial location in the disk. Thirty-two cylindrical plugs of bovine tail NP tissue were subjected to ramp-hold unconfined compression to 20% axial strain in 5% increments, at either 30 μm/s or 0.3 μm/s ramp speeds and the radial displacement determined using biaxial video extensometry. Following radial recoil, the true Poisson's ratio of the solid phase of NP tissue increased linearly with increasing strain and demonstrated strain-rate dependency. The latter finding suggests that the solid matrix undergoes stress relaxation during the test. For small strains, we suggest a Poisson's ratio of 0.125 to be used in biphasic models of the intervertebral disk.
目前关于髓核（NP）组织泊松比的实验数据有限。本研究旨在确定NP组织的泊松比是否与应变相关、与应变率相关，或者是否随椎间盘的轴向位置而变化。对32个牛尾NP组织的圆柱形栓子进行斜坡-保持无侧限压缩，以5%的增量压缩至20%的轴向应变，斜坡速度为30μm/s或0.3μm/s，并使用双轴视频引伸计测定径向位移。在径向回弹后，NP组织固相的真实泊松比随应变增加呈线性增加，并表现出应变率依赖性。后一发现表明，在测试过程中固体基质发生了应力松弛。对于小应变，我们建议在椎间盘的双相模型中使用0.125的泊松比。
