Dynamic Studies of Instability-Triggered Intersonic Surface Detachment Waves in Soft Material Sliding

Abstract

Spatially constrained soft structures under dynamic perturbation may evolve into a variety of organized morphological patterns such as wrinkles and random folds. These surface transformations are usually triggered by system bifurcation instabilities and regulated by energy redistribution. Among them, elastomeric materials sliding on smooth surfaces generate separation pulses due to tangential stress gradients. When the material slides at a speed much lower than those of elastic surface waves, the process is dominated by surface adhesion and relaxation effects coined as Schallamach waves. In contrast, fast traveling separation pulses at the sliding interface exceeding the Rayleigh and shear wave velocities have been theoretically conjectured but not experimentally validated. Besides, the highly dynamic nature of the problem requires a combination of different methods to understand the instability generation mechanisms and evaluate the system responses. Therefore, the purpose of this research is to advance the understanding of the dynamic behavior of instability-triggered detachment waves, and to establish a methodology for more quantitative analyses of the wave propagation, energy transformation and its physical impacts on the surrounding media. Through a synergistic effort combining analytical studies, numerical simulation and experimental observations, we established a framework suitable for the description of: i) mechanisms governing the formation and evolution of separation pulses induced by frictional contact; ii) the necessity and effectiveness of our combined approaches to address the highly nonlinear, multi-scaled dynamic problem; iii) quantitative analysis of the transient wave properties of intersonic surface detachment, and the transformation of energies into other forms (acoustic radiation) during wave propagation in space, and iv) important implications of this work and insights into how the new understanding could shift the landscape of structural design for applications involving soft material contact.