Determination of δ-damping by heterodyne speckle interferometry

In that work we present a method to measure the δ-damping parameter using a heterodyne speckle interferometric set-up. The basic idea to analyze the decrement of the elastic waves consist of exciting longitudinal forced vibrations in a bar, in order to obtain the value of the amplitude of these oscillations as a function of the frequency. The δ-parameter can be measured directly from the resonance frequency and by the width of such a curve. The method was applied to nickel rods and nickel wires, and the results are that damping decreases with the magnetization of the material. That procedure has a high resolution and is more precise than the free vibration method (104. Tagung DGaO (2003), p.96).