PSI - Issue 64

Nikhil Holsamudrkar et al. / Procedia Structural Integrity 64 (2024) 815–821 Holsamudrkar Nikhil et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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2.3. Analysis and filtering

Data analysis was conducted using Python codes developed by the authors. A data filter was applied to the source file to eliminate any generated long waves of low amplitude caused by secondary damage such as friction/shear/sliding. Also, rubber pads were installed at the points of load transfer, such as supports and loading heads, to avoid unwanted noise. 3. Results and Discussion Results are presented as variations of AE cumulative hits, average frequency, rise angle, event rate, historical index, cumulative signal strength, and frequency content over time. AE cumulative hits are defined as the cumulative sum of hits crossing the threshold for a given period of time. AE cumulative hits can be used to monitor damage activity within the material; more hits indicate more damage activity. Cumulative signal strength, or CSS, is a similar parameter to monitor the extent of damage. The RA value is defined as the ratio of rise time and amplitude. RA and average frequency can be used to characterize shear or tensile cracks; shear cracks tend to have longer rise angles and lower frequencies, and vice versa for tensile cracks. Historic index (HI) is the ratio of the cumulative signal strength of recent AE events to that of all AE events. It indicates significant events occurrence in the form of spikes.

Fig. 2. Variation of (a) Cumulative AE hits for different channels wrt time, (b) Average frequency, RA value, Event rate wrt time, (c) Historic index, Cumulative signal strength wrt time, and (d) AF-RA scatter plot for the specimen S2-AN