Ladak Hanif M, Funnell W Robert J, Decraemer Willem F, Dirckx Joris J J
Department of Medical Biophysics, The University of Western Ontario, London, Canada.
J Acoust Soc Am. 2006 May;119(5 Pt 1):2859-68. doi: 10.1121/1.2188370.
Current finite-element (FE) models of the eardrum are limited to low pressures because of the assumption of linearity. Our objective is to investigate the effects of geometric nonlinearity in FE models of the cat eardrum with an approximately immobile malleus for pressures up to +/-2.2 kPa, which are within the range of pressures used in clinical tympanometry. Displacements computed with nonlinear models increased less than in proportion to applied pressure, similar to what is seen in measured data. In both simulations and experiments, there is a shift inferiorly in the location of maximum displacement in response to increasingly negative middle-ear pressures. Displacement patterns computed for small pressures and for large positive pressures differed from measured patterns in the position of the maximum pars-tensa displacement. Increasing the thickness of the postero-superior pars tensa in the models shifted the location of the computed maximum toward the measured location. The largest computed pars-tensa strains were mostly less than 2%, implying that a linearized material model is a reasonable approximation. Geometric nonlinearity must be considered when simulating eardrum response to high pressures because purely linear models cannot take into account the effects of changing geometry. At higher pressures, material nonlinearity may become more important.
由于线性假设，目前的鼓膜有限元（FE）模型仅限于低压情况。我们的目标是研究在锤骨近似固定的猫鼓膜有限元模型中，几何非线性对高达±2.2 kPa压力的影响，该压力范围在临床鼓室图检查所使用的压力范围内。非线性模型计算出的位移增加量小于与施加压力的比例关系，这与测量数据中的情况类似。在模拟和实验中，随着中耳压力越来越负，最大位移位置都会向下移动。小压力和大正压力下计算出的位移模式在紧张部最大位移位置上与测量模式不同。在模型中增加后上紧张部的厚度会使计算出的最大值位置向测量位置移动。计算出的最大紧张部应变大多小于2%，这意味着线性化材料模型是一个合理的近似。在模拟鼓膜对高压的反应时必须考虑几何非线性，因为纯线性模型无法考虑几何形状变化的影响。在更高压力下，材料非线性可能会变得更加重要。
