Volume 40, Issue 5 (September 2012)
Mechanical Impedance Measurement on Thin Layer Surface With Impedance Hammer Device
The mechanical impedance describes the ability of a structure to resist motion when subjected to a given force. It has received increasing attention as a parameter that could influence the tire/road noise in the medium frequency range (630–1600 Hz). In this study, the impedance hammer device is used for measuring the mechanical impedance on thin layer surface mixture samples in the lab. In the test, the excitation is induced by hitting the sample surface with the hammer. Values of the driving force and acceleration of the vibrating slab are recorded. The mechanical impedance can then be calculated from the ratio of the force to the velocity that is obtained by integration of the acceleration. The influence of the material properties were investigated by comparing the results on different samples. A further measurement of dynamic stiffness on the same material is also discussed and related to the hammer measurement.