31. Analysis of Contact Dynamics Using Controlled Impact Excitations

In the current work, the contact dynamics during impact is analyzed using a repeatable impact excitation system. In general, accurate description of force-deformation relationship during a dynamic impact event necessitates using semi-empirical or empirical models. The validity of these models under different conditions (the shape, material, surface condition, and impact velocity of the impacting bodies) depends on accurate experimental calibration of model parameters. As such, an effective and reproducible calibration approach is critical to obtaining effective contact dynamics models. The prevailing calibration approaches for impact dynamics focus on identifying only one of those parameters, the coefficient of restitution (CoR), and only for limited range of impact conditions. Estimating the contact stiffness and the power law exponent requires direct, precise and simultaneous measurement of force and sub-micron level deformation (indentation). Furthermore, calibration and modeling uncertainty must be well understood to determine the applicability of the contact-dynamics models. To address these challenges, the objective of the current work is to use a repeatable impact excitation system (IES) and interferometry to enable calibration of contact dynamics models. The IES enables precise control of impact velocities, and high-resolution interferometric (Laser Doppler Vibrometer, LDV) measurement of impacted surface and impact tip provides accurate determination of the associated deformations. After describing the approach in detail, we present demonstrative case studies on stainless steel and aluminum surfaces, and obtain the calibration parameters for different models presented in the literature. During the calibration, the force and deformations levels are varied by controlling the velocity of the impact. Furthermore, an uncertainty quantification is conducted to determine uncertainties of determined parameters to better identify the validity of the calibrated model, as well as the capability of the approach. It is concluded that the presented approach is an effective means of calibrating and validating various contact dynamics models at different impact velocities.