An experimental method for determining the effects of strain gradients in a granular material.

The paper presents an algorithm for use with the discrete element method to study possible strain-gradient effects in granular materials. The algorithm produces an intentionally non-uniform displacement pattern by applying external (body) forces to the particles within a simulated granular assembly. The paper describes a method for adjusting the external forces to attain the intended gross displacement pattern, but while allowing individual particles to be in equilibrium among neighbouring particles. The performance of the algorithm is tested in an example of quasi-static deformation, and the algorithm's performance is measured in three respects. The algorithm is shown to enforce the intended displacement pattern, to allow particles to equilibrate among neighbouring particles, and to produce a smooth distribution of the external forces among particles. Copyright © 2003 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]