Experimental investigation and finite element modelling of a new high damping metallic material

The properties of a high damping metallic material are investigated experimentally and a plausible finite element (FE) representation based on the results is deduced. The material consists of hollow, bonded aluminium spheres filled with ceramic particles. The damping mainly occurs due to dissipation via particle interaction. Consequently, one has to model the damping in such a way that shearing contributes only a little to the energy dissipation and the damping properties are orthotropic while the material stiffness is isotropic. Using the model of constant hysteresis for frequency-domain calculations, the complex stiffness matrix is constructed from the real-valued isotropic stiffness matrix, and the complex-valued orthotropic damping matrix. Since the finite element code used only offers the possibility of the damping matrix of an element being proportional to its stiffness, two superimposed finite element models are utilized, one representing the material's stiffness the other it's damping properties. The material parameters are obtained from an experimental modal analysis (EMA) on three samples of the material. The modelling approach is verified on a single hexahedral element and a simulation of the experimental modal analysis. Finally, a sandwich frame structure consisting of the damping material sandwiched between two aluminium frames is investigated by means of an EMA and a respective finite element modal analysis which makes use of the aforementioned modelling approach. A comparison of the results is given in terms of eigenfrequencies and the corresponding modal damping measures.