Damage identification in concrete using impact non-linear reverberation spectroscopy

•We model the free reverberation from a standard impact resonance frequency test.•Resonance frequency and damping is expressed as a non-linear function of time.•Results are extracted over a wide dynamic range and true physical amplitude.

High amplitude non-linear acoustic methods have shown potential for the identification of micro damage in brittle materials such as concrete. Commonly, these methods evaluate a non-linearity parameter from the relative change in frequency and attenuation with strain amplitude. Here, a novel attenuation model is introduced to describe the free reverberation from a standard impact resonance frequency test, together with an algorithm for estimating the unknown model coefficients. The non-linear variation can hereby by analyzed over a wider dynamic range as compared to conventional methods. The experimental measurement is simple and fully compatible with the standardized free-free linear impact frequency test.