PSI - Issue 13

I.Yu. Smolin et al. / Procedia Structural Integrity 13 (2018) 1059–1064 I.Yu. Smolin et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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4. Conclusion

An analysis of the time series reflecting the evolution of the loaded specimen deformation up to catastrophic failure showed that the deformation process is autocorrelated and thus corresponds to the states of dynamical chaos and of self-organized criticality in isolated areas where the correlation coefficient is rather high. The spectral analysis and 2D hodograph of the signal fast Fourier transform complex vector revealed the multiscale structure of fracturing, which is confirmed by the fractal character of the hodograph. The equivalence of the zoomed hodograph fragments to the original picture demonstrates the multiscale nature of the deformation and subsequent failure of the specimen. Moreover, a sharp change in the hodograph structure corresponding to the increase in the fracture scale is observed only near a catastrophic event, which can be regarded as a precursor to catastrophic failure. The wavelet analysis using symmetric Daubechies wavelets reveals well short signal peaks corresponding to local fracturing. The cross-correlation analysis by the moving window method showed that a high level of correlation of a catastrophic event (failure of the specimen) with the periods of the previous process of accumulation of damage and fracturing is observed only in a very short time interval. This time interval does not exceed 8 – 10 times of the failure critical stage (the sharp and steady increase of the specimen surface velocity). Since a confident prognosis is possible only in the correlation region, then the revealed time interval seems to be extremely small for the real forecast.

Acknowledgements

The work was carried out within the framework of the Fundamental Research Program of the State Academies of Sciences for 2013 – 2020, the line of research III.23, and with the support of the Tomsk State University competitiveness improvement program.

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