Abstract
Pressure shear plate impact tests have revealed that when normal stress changes rapidly enough, the frictional shear resistance is no longer proportional to the normal stress but rather evolves with slip gradually. Motivated by these findings, we focus on characterizing the dynamic shear strength of frictional interfaces subject to rapid variations in normal stress. To study this problem, we use laboratory experiments featuring dynamic shear cracks interacting with a free surface and resulting in pronounced and rapid normal stress variations. As dynamic cracks tend to propagate close to the wave speeds of the material, capturing their behavior poses the metrological challenge of resolving displacements on the order of microns over timescales microseconds. Here we present our novel approach to quantify the full-field behavior of dynamic shear ruptures and the evolution of friction during sudden variations in normal stress, based on ultrahighspeed photography (at 1-2 million frames/sec) combined with digital image correlation. Our measurements allow us to capture the evolution of dynamic shear cracks during these short transients and enable us to decode the nature of dynamic friction.
Highlights
The study of dynamic shear cracks along frictional interfaces is relevant to a wide range of problems, including fiber pull-out in the failure of composite materials, airplane actuators, and earthquakes
We have developed an approach based on ultrahigh-speed digital image correlation (DIC) [15, 16] that enables us to quantify the full-field behavior of dynamic ruptures [17, 18] and the evolution of dynamic friction [19]
In this study we have shown the behavior of dynamic shear cracks approaching and interacting with a free surface, using ultrahigh-speed photography coupled with digital image correlation
Summary
The study of dynamic shear cracks along frictional interfaces is relevant to a wide range of problems, including fiber pull-out in the failure of composite materials, airplane actuators, and earthquakes. One key feature of our experimental setup is that it is able to produce and record rapid normal stress variations during dynamic rupture next to the intersection of the interface with the side free surface [11], and it is well suited to study this problem. Previous versions of this experimental setup have been successfully used to reproduce a number of dynamic rupture phenomena, including supershear transition, bimaterial effect, and pulse-like rupture propagation [5, 2022]. We discuss our dynamic measurements and analysis aimed at understanding the evolution of the shear resistance in response to rapid normal stress variations, based on our recent advances [23]
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