Waves in fractal media

Paul N. Demmie, Martin Ostoja-Starzewski

Research output: Contribution to journalArticlepeer-review

Abstract

The term fractal was coined by BenoÎt Mandelbrot to denote an object that is broken or fractured in space or time. Fractals provide appropriate models for many media for some finite range of length scales with lower and upper cutoffs. Fractal geometric structures with cutoffs are called pre-fractals. By fractal media, we mean media with prefractal geometric structures. The basis of this study is the recently formulated extension of continuum thermomechanics to such media. The continuum theory is based on dimensional regularization, in which we employ fractional integrals to state global balance laws. The global forms of governing equations are cast in forms involving conventional (integerorder) integrals, while the local forms are expressed through partial differential equations with derivatives of integer order. Using Hamilton's principle, we derive the equations of motion of a fractal elastic solid under finite strains. Next, we consider one-dimensional models and obtain equations governing nonlinear waves in such a solid. Finally, we study shock fronts in linear viscoelastic solids under small strains. In all the cases, the derived equations for fractal media depend explicitly on fractal dimensions and reduce to conventional forms for continuous media with Euclidean geometries upon setting the dimensions to integers.

Original languageEnglish (US)
Pages (from-to)187-204
Number of pages18
JournalJournal of Elasticity
Volume104
Issue number1-2
DOIs
StatePublished - Aug 2011

Keywords

  • Elastic materials
  • Fractals
  • Micromechanical theories
  • Waves

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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