Comparison between a type of vibro-acoustic modulation and damping measurement as NDT techniques

The sensitivities of the conventional damping test and a particular implementation of the emerging vibro-acoustic modulation NDT technique have been compared on three types of cracked specimens: (1) a set of mild steel beams cracked in the laboratory, (2) a perspex beam also cracked in the laboratory and (3) an industrial component made of a nickel-based alloy. The latter was forged and cracked in the forging process. The comparison showed very similar performances on the specimens used. Both techniques work best for lightly damped specimens and in setups such that the influence of the support can be minimised. Their sensitivity is severely affected when these two conditions are not satisfied which significantly lower their appeal for many practical situations.