Monday  |  Salon 12  |  05:00 PM–05:20 PM

#18659–Numerical Investigation of the Influence of Elastic Bandgaps on Plastic Wave Propagation

We explore the dynamics of plastic wave propagation in a periodic, one-dimensional acoustic medium (i.e., phononic crystal). First, we establish the principles governing the propagation of elastic and plastic waves in uniform, one-dimensional rods using the method of characteristics. Subsequently, we employ a semi-analytical (SA) approach, based on the numerical application of the method of characteristics on a fine mesh in space and time, to predict the propagation and behavior of plastic waves in one-dimensional media with spatially varying cross-sectional area profiles. The SA procedure is validated using time-domain finite element simulations for harmonic excitation at plastic amplitudes. Further, we examine a phononic crystal based upon a dogbone-shaped unit cell, investigating its elastic band structure and predicting its response to both elastic and plastic amplitude excitation using the developed semi-analytical method. We focus specifically on the effect of elastic bandgaps on plastic wave propagation and resultant residual strains. To experimentally verify the predicted results, we design and fabricate a discrete, nonlinear phononic crystal and study its response at frequencies within the elastic bandgap range. Using a spring system consisting of slider elements and linear springs, we implement hysteretical elastic-plastic spring behavior between the phononic crystal’s discrete masses, thus enabling plastic amplitude excitation in a highly repeatable laboratory setting. With the semi-analytical procedure and its subsequent experimental verification, we establish the basis for the further study of pulse shaping in plastic phononic crystals, a subject of interest for applications related to high-amplitude dynamic loads such as the split Hopkinson bar pressure test.

Greg Dorgant   Georgia Institute of Technology
Washington DeLima   Kansas City National Security Campus
Michael Leamy   Georgia Institute of Technology