Noël Christophe
Institut national de recherche et de sécurité (INRS), 1 rue du Morvan, CS 60027 - F-54519 Vandœuvre cedex, France.
Med Eng Phys. 2018 Nov;61:41-50. doi: 10.1016/j.medengphy.2018.08.007. Epub 2018 Sep 24.
This study lays the groundwork for a multi-scale strategy that will lead to a better understanding and prediction of the effects of vibration on the digital arterial network. This is accomplished by modelling the mechanical and biological factors that could disturb the basal vasoconstriction balance in the fingertip. The first stage of this novel approach involved building and validating an original dissipative constitutive law for the fingertip soft tissue for the purpose of finite element modelling of the mechanical response of preloaded phalanges in vibration. This visco-hyperelastic constitutive law was established by means of a two-stage procedure for combining a classical pure static nonlinear law with an original dissipative model. First, the parameters of an Ogden-Hill pure static nonlinear constitutive law were identified using a constrained optimisation algorithm. Second, an original viscous dissipation model was proposed in the spectral domain. This model is based on the linearization of the nonlinear quasi-linear viscoelasticity law and the use of a viscoelastic relaxation modulus, expressed as a continuous distribution of relaxation spectra suitable for living tissues. The experimental data used to fit this model were the static and dynamic stiffnesses of preloaded fingertips acquired from a group of 20 subjects. The relative errors between the measured and simulated stiffnesses were less than 5% in the static procedure and approximately 8% using dynamic analysis. The computed mechanical pressure and maximal tangential stress within the fingertip were high in the soft tissues close to the vibration excitation and also in the bones and interphalangeal cartilages far from the vibration source. Mechanical power was only dissipated significantly in the immediate vicinity of the contact area between the probe and the finger. The main contribution of this study was to implement and identify the parameters of a new spectral dissipative law for fingertip soft tissues. This work may apply in occupational health for modifying the vibration dose assessment or for the follow-up and screening of connective tissue diseases.
本研究为多尺度策略奠定了基础，该策略将有助于更好地理解和预测振动对指动脉网络的影响。这是通过对可能扰乱指尖基础血管收缩平衡的机械和生物因素进行建模来实现的。这种新方法的第一阶段涉及建立并验证一种针对指尖软组织的原始耗散本构定律，用于对振动中预加载指骨的机械响应进行有限元建模。这种粘弹性本构定律是通过一个两阶段程序建立的，该程序将经典的纯静态非线性定律与原始的耗散模型相结合。首先，使用约束优化算法确定奥格登 - 希尔纯静态非线性本构定律的参数。其次，在谱域中提出了一种原始的粘性耗散模型。该模型基于非线性准线性粘弹性定律的线性化以及使用粘弹性松弛模量，该模量表示为适合活体组织的松弛谱的连续分布。用于拟合该模型的实验数据是从一组20名受试者获取的预加载指尖的静态和动态刚度。在静态过程中，测量刚度与模拟刚度之间的相对误差小于5%，使用动态分析时约为8%。在靠近振动激励的软组织中以及远离振动源的骨骼和指间软骨中，计算得到的指尖内机械压力和最大切向应力都很高。机械功率仅在探头与手指接触区域的紧邻区域显著耗散。本研究的主要贡献是实现并确定了一种针对指尖软组织的新谱耗散定律的参数。这项工作可能应用于职业健康领域，用于修改振动剂量评估或用于结缔组织疾病的随访和筛查。
