Ghost internal friction peaks, ghost asymmetrical peak broadening and narrowing: Misunderstandings, consequences and solution

The effect of the ‘Zero-Point Drift’ (ZPD) on computed values of the logarithmic decrement from decaying harmonic oscillations is reported. It is shown that the ZPD modifies the shape of exponentially damped harmonic oscillations and leads to false values of the logarithmic decrement if computed according to the classical algorithms. This procedure can readily create ghost internal friction peaks, ghost asymmetrical peak broadening and/or narrowing. This means, that the shape, the height, and the symmetry of internal friction peaks are strongly affected by the ZPD. A solution of the problem of computing the logarithmic decrement in the presence of different ZPD is provided. It is demonstrated that the ‘Optimization in Multiple Intervals’ algorithm is the proper way to compute the logarithmic decrement for all damping levels in the presence of various types of Zero-Point Drift.