Investigating the effect of dry-friction on damage detection tests

This paper investigates whether dry-friction can affect the detection of damages in the context of structural dynamics tests. The problem is confronted through a MDOF system with a single Coulomb contact and a harmonic excitation, in the presence of two damage scenarios, namely the loss of a member connectivity and a reduction of the artificial damping, also considering different locations of the frictional contact and the input excitation. In particular, we derive the trends of the damage signature with respect to the friction-over-excitation ratio. In this way, it was possible to correlate the amplitude of the damage signature to the properties of the system in the stick–slip or in the stuck regime. The investigation is also pursued through experimental tests with the same damage scenarios applying a variation of the friction ratio of one order of magnitude. Results confirm the theoretical trends and suggest that the choice of the friction ratio can also determine the appearance of false negatives for a given confidence level.