Constitutive model for special granular structures

This work deals with novel “smart systems” that are based on granular materials. These systems consist of mechanical components, such as a beam or bar, enclosed in a tight flexible sleeve that is filled with a granular material. When air is pumped out of the sleeve, the resulting underpressure causes the compression of the granules making the system more rigid and changing its damping characteristics. This allows for quick, easy, and inexpensive control of the damping and stiffness of such a system. This paper presents the experimental results of uniaxial tensile tests of a sleeve filled with different granular materials. These results support the modeling of the mechanics of such a system with the Chaboche viscoplastic constitutive law. The experiments provide the quantitative and functional dependence of the model parameters on the underpressure, which acts as the control variable. The highly non-linear dependence of the system's fundamental mechanical properties on the underpressure is described and discussed. This basic work opens the way to applications in mechanical systems where effective control of vibrations or noise is important.