|Damping plays an important role in technical practice. Coulomb (1784) (Memoir on Torsion) describes experiments where damping in torsional vibrations is due to material defects, while according to Lazan it is important for many load types. Degradation of structural integrity of materials is related to strength decrease. Evaluation of the effect of defects on materials strength, especially in fatigue and brittle fracture, is very important consideration in engineering technology. Pre-existing pores, cracks and flaws, in addition to those produced during service due to fatigue or static loading, influence the behavior of a material towards mechanical stresses. The presence of a defect (i.e. pore, crack) in a structural member according to Dimarogonas introduces a local flexibility affecting its vibration response and depending on the vibration amplitude, thus leading to a coupled system, with new harmonics in the spectrum. [Panteliou SD (2012) Damping As Structural Integrity Index].