Damping characterization of magnesium based composites using an innovative circle-fit approach

In the present study, a new methodology of using free-free method coupled with circle-fit approach is used to determine damping of ceramic reinforced magnesium composites. This technique is based on classical vibration theory, by which the geometry and material properties of the metal matrix composites are related to the resonant frequency and structural damping of the test specimen. Using the fact that the ratio of the vibration response to the applied force fits to a circle in the Argand plane for each resonant frequency of the test specimen, the damping factor and natural frequency are predicted accurately for the test specimen. An attempt is made to rationalize the increase in damping capability of the MMC when compared against the monolithic specimen in terms of increase in density of the dislocations and presence of plastic zones due to thermal mismatch between the two phases, as well as due to the presence of extrinsic damping mechanisms such as elasto-thermodynamic damping.