Experimental Mechanics

, Volume 53, Issue 3, pp 327-337

First online:

Directional Wave Propagation in a Highly Nonlinear Square Packing of Spheres

  • A. LeonardAffiliated withDepartment of Engineering and Applied Science, California Institute of Technology
  • , F. FraternaliAffiliated withDepartment of Civil Engineering, University of Salerno
  • , C. DaraioAffiliated withDepartment of Engineering and Applied Science, California Institute of Technology Email author 

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We studied the dynamic response of a two-dimensional square packing of uncompressed stainless steel spheres excited by impulsive loadings. We developed a new experimental measurement technique, employing miniature tri-axial accelerometers, to determine the stress wave properties in the array resulting from both an in-plane and out-of-plane impact. Results from our numerical simulations, based on a discrete particle model, were in good agreement with the experimental results. We observed that the impulsive excitations were resolved into solitary waves traveling only through initially excited chains. The observed solitary waves were determined to have similar (Hertzian) properties to the extensively studied solitary waves supported by an uncompressed, uniform, one-dimensional chain of spheres. The highly directional response of this system could be used as a basis to design granular crystals with predetermined wave propagation paths capable of mitigating stress wave energy.


Two-dimensional square packing Granular crystals Highly nonlinear dynamics Directional wave propagation Impulsive excitation