PSI - Issue 64

Ina Reichert et al. / Procedia Structural Integrity 64 (2024) 145–152 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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The forward calculation part of the DENISE program generates “real” measurement data that can be seen as artificially created measurement data without noise. In a second step noise is added to this data with the signal-to noise ratios of 100, 50, 20 and 10. This results in five artificial data sets for each defect’s size, position and distance between the sources and receivers, which are equal in this case study. The initial models without any defect for the FWI are exemplarily given in Fig. 2 for three different sensor distances. In total, there were ten different sensor differences from 1 m to 10 m in one-meter-steps applied. Additionally, the inversion procedure follows a regime, where the frequency bands are increased and decreased in circles. This approach helps to diminish unintended artifacts in the model parameters as described in Alalade et al. (2018). The regime is depicted in Fig. 3.

Fig. 3. Frequency stages for the iteration stages of the Full Waveform Inversion procedure

4. Results The FWI results of combination 2 with a sensor distance of 1 m and no noise is depicted during the passing of the iteration stages (cf. Fig. 3) in Fig. 4.

Fig. 4. Model parameter development during the course of iteration stages of the FWI, maximum of frequency band is given in the subfigures; size and position of real ellipse marked with red dashed line