[4A2] Measurements of material non-linearity using collinear wave mixing for transient inputs
Z Ebrahim-Saib, A J Croxford and B W Drinkwater
University of Bristol, UK
Most non-destructive testing methods aim at detecting and sizing relatively large defects, which tend to occur at the end of the life of a structure. Early-stage defects or damage precursors such as plasticity and cracks are associated to material non-linearity and are challenging to measure. Non-linear ultrasound has shown its sensitivity to early damage formation such as microcracks and the onset of plasticity. In particular, the wave mixing method has shown promising results in the 1D mapping of non-linearity and its relation to fatigue life. Conventionally, these measurements are relative as most studies are interested in the trend of non-linearity. However, non-linear wave mixing has the potential to obtain absolute values of non-linearity within a material and thus could be used to deduce values for third-order elastic constants for material. One main difficulty is that the theoretical amplitudes expected are based on rectangular waveform inputs, which is not the case when practical transducers are used. This study provides the theoretical framework to correct for transient inputs for the specific case when there is two-way mixing of shear and longitudinal waves. The correction factor is then used to evaluate the third-order elastic constant of aluminium experimentally. Its trend with increasing plasticity will be explored in the future.
Acknowledgements: Funding from EPSRC FIND CDT and the University of Bristol.
Acknowledgements: Funding from EPSRC FIND CDT and the University of Bristol.
