Abstract
The nonlinear elastic response of consolidated granular or damaged materials is the result of the combination of nonlinear attenuation and velocity, coupled with hysteresis, which is linked to non equilibrium effects (often termed conditioning). Thus, a preliminary step towards the comprehension of the physical mechanisms responsible of the nonlinear elastic behaviours consists in quantifying and separating the various contributions. To this purpose, an approach based on a semi-analytical treatment of signals resulting from a monochromatic continuous wave excitation can be successfully implemented. Its validation is discussed here, applying the proposed approach to the analysis of numerical data obtained by using a finite difference spring model code. The accuracy, sensibility and robustness of the protocol are verified in different nonlinear conditions.
Highlights
Materials with a very different microstructure, including consolidated [1,2,3,4,5] and unconsolidated [6] granular media or damaged composites and metallic materials [7,8,9,10,11], share a very similar elastic behaviour, in which hysteresis plays a crucial role
Consolidated granular materials feature grain contacts, which may give rise to sliding [18] and/or static friction [19], together with adhesion mechanisms linked to the nonlinear behaviour due to the presence of water at the interfaces between microcracks faces [20,21]
The curves are straight lines with slope 2, except for velocity in Case 4
Summary
Materials with a very different microstructure, including consolidated [1,2,3,4,5] and unconsolidated [6] granular media or damaged composites and metallic materials [7,8,9,10,11], share a very similar elastic behaviour, in which hysteresis plays a crucial role Their nonlinear response to an ultrasonic excitation is governed by a combination of effects due to velocity dependence on strain and attenuation nonlinearity [12,13,14,15]. In damaged composites, open or partially open cracks, responsible for clapping [22,23]
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