Vibro-acoustic modulation for damage detection -investigation of nonlinear effects for contact-type damage.

The paper presents experimental investigation of nonlinear effects in vibro-acoustic modulation test, generated due to contact-type nonlinearity. The two samples with prepared contact surfaces were tested in experimental works. Two excitation types: low and high frequencies are introduced into the structure via electromagnetic shaker and piezoelectric transducer respectively, to produce contact-related nonlinear effects. The contact surfaces are driven to move relative to each other in two types of motion: micro slip and stick and slip. The motion types are classified according to displacement values using laser vibrometer. For given scenario the analysis of nonlinearities is performed based on signal response. The paper focus on investigation of both sidebands distribution around carrier frequency and higher harmonics of low frequency excitation.