Nonlinear acoustics for fatigue crack detection – experimental investigations of vibro-acoustic wave modulations

TLDR

The study investigates vibro‑acoustic nonlinear wave modulations in a cracked aluminum plate, focusing on how low‑frequency vibration excitation affects modulation intensity and nonlinear wave interaction mechanisms. The authors experimentally examine these modulations by exciting a cracked aluminum plate with low‑frequency vibrations and measuring the resulting nonlinear wave interactions. They find that energy dissipation—not crack opening–closing—is the primary source of nonlinear modulations, allowing crack detection with weak strain fields and demonstrating a clear link to thermo‑elastic coupling that supports a non‑classical vibro‑acoustic interaction mechanism.

Abstract

Vibro-acoustic nonlinear wave modulations are investigated experimentally in a cracked aluminum plate. The focus is on the effect of low-frequency vibration excitation on modulation intensity and associated nonlinear wave interaction mechanisms. The study reveals that energy dissipation – not opening–closing crack action – is the major mechanism behind nonlinear modulations. The consequence is that relatively weak strain fields can be used for crack detection in metallic structures. A clear link between modulations and thermo-elastic coupling is also demonstrated, providing experimental evidence for the recently proposed non-classical, nonlinear vibro-acoustic wave interaction mechanism.