Uncertainty Analysis of Dynamic Rupture Measurements Obtained Through Ultrahigh-Speed Digital Image Correlation

Abstract

Background: The full-field behavior of dynamic shear cracks, with their highly transient features, has recently been quantified by employing Digital Image Correlation (DIC) coupled with ultrahigh-speed photography (at 1-2 million frames/sec). The use of ultrahigh-speed DIC has enabled the observation of complex structures associated with the evolution of the dynamic shear fractures under controlled laboratory conditions, providing a detailed description of their distinctive full-field kinematic features. This has allowed to identify, for instance, the spatiotemporal characteristics of sub-Rayleigh and intersonic shear ruptures, and to measure the evolution of dynamic friction during rupture propagation of frictional shear ruptures. Objective: Capturing such highly transient phenomena represents a challenging metrological process influenced by both ultra-fast imaging procedures and DIC analysis parameters. However, the effect of these parameters on the quantification of the rupture features has not been assessed yet. Here, a simulated experiment framework is presented and employed to evaluate the uncertainties associated with ultrahigh-speed DIC measurements. Methods: Finite element simulations replicate laboratory experiments of dynamic ruptures spontaneously propagating along frictional interfaces. Experimental images of the specimen acquired with an ultrahigh-speed camera are numerically deformed by the displacement fields obtained from the numerical simulations and are analyzed using the same DIC analysis procedure as in the laboratory experiments. Results: The displacement, particle velocity, and strain fields obtained from the DIC analysis are compared with the ground-truth fields of the numerical simulations, correlating the measurement resolution with the physical length scale of the propagating Mode II rupture. In addition, the full-field data are employed to estimate the capability of the ultrahigh-speed DIC setup to infer the dynamic friction evolution. Conclusions: This methodology allows us to quantify the accuracy of the ultrahigh-speed DIC measurements in resolving the complex spatiotemporal structures of dynamic shear ruptures, focusing on the impact of the key correlation parameters.