To validate models of contact mechanics in low speed structural impact, slender rods were impacted in a drop tower, and measurements of the contact and vibration were compared to analytical and finite element (FE) models. The contact area was recorded using a novel thin-film transfer technique, and the contact duration was measured using electrical continuity. Strain gages recorded the vibratory strain in one rod, and a laser Doppler vibrometer measured speed. The experiment was modeled analytically on a one-dimensional spatial domain using a quasi-static Hertzian contact law and a system of delay differential equations. The three-dimensional FE model used hexahedral elements, a penalty contact algorithm, and explicit time integration. A small submodel taken from the initial global FE model economically refined the analysis in the small contact region. Measured contact areas were within 6 % of both models’ predictions, peak speeds within 2 %, cyclic strains within 12 με (RMS value), and contact durations within 2 μs. The global FE model and the measurements revealed small disturbances, not predicted by the analytical model, believed to be caused by interactions of the non-planar stress wavefront with the rod’s ends. The accuracy of the predictions for this simple test, as well as the versatility of the diagnostic tools, validates the theoretical and computational models, corroborates instrument calibration, and establishes confidence that the same methods may be used in experimental and computational study of contact mechanics during impact of more complicated structures. Recommendations are made for applying the methods to a particular biomechanical problem: the edge-loading of a loose prosthetic hip joint which can lead to premature wear and prosthesis failure.

中文翻译：

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细长杆的接触耦合影响：分析和实验验证

为了验证低速结构冲击下的接触力学模型，细长杆在落塔中受到冲击，接触和振动的测量结果与分析和有限元 (FE) 模型进行了比较。使用新型薄膜转移技术记录接触面积，并使用电连续性测量接触持续时间。应变计记录一根杆的振动应变，激光多普勒振动计测量速度。该实验使用准静态赫兹接触定律和延迟微分方程系统在一维空间域上进行分析建模。三维有限元模型使用六面体元素、惩罚接触算法和显式时间积分。取自初始全局有限元模型的小子模型在小接触区域中经济地完善了分析。测量的接触面积在两个模型预测的 6% 以内，峰值速度在 2% 以内，循环应变在 12 με（RMS 值）以内，接触持续时间在 2 μs 以内。全局 FE 模型和测量结果揭示了分析模型无法预测的小扰动，据信是由非平面应力波前与杆端的相互作用引起的。这种简单测试预测的准确性以及诊断工具的多功能性验证了理论和计算模型，证实了仪器校准，并建立了信心，即相同的方法可用于接触力学的实验和计算研究中更复杂结构的影响。