Wu J Z, Dong R G, Rakheja S, Schopper A W
National Institute for Occupational Safety and Health, Morgantown, West Virginia 2650, USA.
Med Eng Phys. 2002 May;24(4):253-64. doi: 10.1016/s1350-4533(02)00018-8.
Extended exposure to mechanical vibration has been related to many vascular, sensorineural and musculoskeletal disorders of the hand-arm system, frequently termed 'hand-arm vibration syndrome' (HAVS). A two-dimensional, nonlinear finite element model of a fingertip is developed to study the stress and strain fields of the soft tissue under dynamic loading, that may be encountered while grasping and operating a hand-held power tool. The model incorporates the most essential anatomical elements of a fingertip, such as soft tissue, bone, and nail. The finger is assumed to be in contact with a steel plate, simulating the interaction between the fingertip and a vibrating machine tool or handle. The soft tissue is assumed to be nonlinearly visco-elastic, while the nail, bone, and steel plate are considered to be linearly elastic. In order to study the time-dependent deformation behavior of the fingertip, the numerical simulations were performed under ramp-like loading with different ramping periods and sinusoidal vibrations of the contacting plate at three different frequencies (1, 10, and 31.5 Hz). Owing to relatively large deformations of the soft tissue under specified static and dynamic loading, Lagrangian large deformation theory was applied in the present analysis. The effects of the loading rate and the frequency of the sinusoidal vibration on the time-dependent strain/stress distributions in the different depth within the soft tissue of the fingertip are investigated numerically. Our simulations suggest that the soft tissue of the fingertip experiences high local stress and strain under dynamic loading and the fingertip may separate from the vibrating contact surface due to the viscous deformation behaviour of the soft tissue. For a given deformation, the high frequency loading produces a higher stress in the tissues compared to that obtained at a low frequency loading. The present model may serve as a useful tool to study the mechanism of tissue degeneration under vibratory loading encountered during operation of hand-held power tools.
长期暴露于机械振动与手臂系统的许多血管、感觉神经和肌肉骨骼疾病有关，这些疾病通常被称为“手臂振动综合征”（HAVS）。本文建立了一个指尖的二维非线性有限元模型，以研究在抓握和操作手持式电动工具时可能遇到的动态载荷下软组织的应力和应变场。该模型包含了指尖最基本的解剖元素，如软组织、骨骼和指甲。假设手指与钢板接触，模拟指尖与振动机床或手柄之间的相互作用。假设软组织为非线性粘弹性，而指甲、骨骼和钢板为线性弹性。为了研究指尖随时间变化的变形行为，在具有不同斜坡周期的斜坡状载荷以及接触板在三种不同频率（1、10和31.5Hz）下的正弦振动下进行了数值模拟。由于在特定的静态和动态载荷下软组织的变形相对较大，本分析采用了拉格朗日大变形理论。数值研究了加载速率和正弦振动频率对指尖软组织不同深度处随时间变化的应变/应力分布的影响。我们的模拟表明，指尖的软组织在动态载荷下会经历高局部应力和应变，并且由于软组织的粘性变形行为，指尖可能会与振动接触表面分离。对于给定的变形，高频加载在组织中产生的应力比低频加载时更高。本模型可作为研究手持式电动工具操作过程中遇到的振动载荷下组织退化机制的有用工具。
