On the possible applications of the non-linear acoustic phenomena for the evaluation of the granular materials (original) (raw)

Granular materials are widely used in different brunches of industry from the building construction to pharmaceutical and production of the nanostructured materials. Classical acoustical methods for their diagnostics are well known to be very useful. By the present communication we would like to attract the attention to the possible applications of the emerging nonlinear acoustical methods for the nondestructive evaluation of the granular materials. Three potential applications are discussed. First, due to high nonlinearity of the granular materials the parametric emitting antenna can operate with sufficient efficiency in these materials. Thus, similar to the advantages achieved in underwater applications of the parametric sonar, compact sources of highly directive low-frequency sound waves can be created for the acoustic spectroscopy, tomography and depth-profiling of the granular piles and columns. Second, due to high sensitivity of the nonlinear phenomena to the state of the inter-grain contacts, such processes involving polarized shear waves are sensitive to the force chains network through its anisotropy when a uniaxial static stress is applied on the medium. Finally, few results related to a recently developed model describing the parametric antenna operation in a uni-dimensional chain of identical elastic beads are discussed. Discrete feature of the lattice and evanescent modes are taken into account.