Measurement of slip and separation in jointed structures with non-flat interfaces.

• Digital image correlation is used to visualize the local kinematic behaviors of a jointed interface. • Test specimens include perturbations of the Brake-Reuß beam that have curved interfaces. • Results directly invalidate many assumptions common to the modeling of jointed structures. • In the first mode of the systems, both separation and microslip are observed. • For the second mode of all of the test specimens, macroslip is observed for a 5 N excitation. The nonlinear dynamic behavior and energy dissipation of a built-up structure are often attributable to the contact interfaces between the subcomponents of the structure. Due to the lack of direct measurement techniques for jointed interfaces, the local kinematic behaviors inside the interfaces are not well understood. Additionally, the part-to-part variability of the interface (such as surface curvature, surface roughness, geometric features, and residual stress) significantly affects the structural dynamics and, therefore, introduces uncertainty in the measured response of a jointed structure. In this paper, the local kinematic behavior of a jointed interface is measured by digital image correlation (DIC) during shaker excitation at the first two resonant frequencies for 10 different perturbations of the same assembled structure. For these perturbations, the interface curvature is varied to represent typical manufacturing variations. Experimental validation shows that the DIC method is able to measure slip and separation in the interface with a resolution of up to 0.23 μm for the reported experiments. Additionally, the nonlinear properties of the system are characterized via impact hammer test. For the first mode of the structure, separation (clapping) and microslip behaviors are observed; additionally, for the second mode, macroslip motions are observed. These results challenge multiple assumptions prevalent in the modeling of jointed structures. [ABSTRACT FROM AUTHOR]