Experimental investigation of wave velocity and dynamic contact stresses in an assembly of disks

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Dynamic photoelasticity and strain-gage techniques are employed to study wave propagation and dynamic load transfer in granular media. The granular medium is modeled as one- and two-dimensional deterministic and random arrays of circular disks of polyester material Homalite 100. The dynamic loading is achieved by explosive excitation. The experimental data are analyzed to determine the wave velocities, to identify the characteristic load transfer paths, and to quantitatively obtain the dynamic contact forces in the granular assembly. It is observed that the wave-propagation and dynamic-load-transfer phenomenon depends on the disk diameter and the obliqueness and flexibility of the load-transfer paths. The wave speed drops significantly in the first few granules after which the decay is more gradual. The load transter is characterized by the contact length and the friction between the contacting granules. The peak loads drop as the distance of the contact points from the point of explosive loading increases. For two-dimensional wave propagation, the load-transfer paths and the magnitude of contacting forces depend on the angles made by the normals of the contacting disks at the contact point. © 1987 Society for Experimental Mechanics, Inc.

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Experimental Mechanics