PSI - Issue 80

Yuhang Pan et al. / Procedia Structural Integrity 80 (2026) 43–52

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YuhangPan / Structural Integrity Procedia 00 (2023) 000–000

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Fig. 8: The framework of the proposed method in this work.

As shown in Fig.8, the results obtained from Sensor 2 for specimen T1 display slight di ff erences in ampli tude compared with those from Sensor 1. However, the overall trend of the RMS change remains consistent between the two sensors. More importantly, application of the proposed DPL method to the Sensor 2 data identified the same critical point, corresponding to a crack length of 0.7 mm at approximately 92,000 cycles. This result is in agreement with the detection obtained from Sensor 1, thereby confirming the consistency of the proposed approach across di ff erent sensor locations and further demonstrating its robustness for practical applications. This study systematically investigated baseline-free online crack detection, extending our previous work on the second and third harmonic parameters. Although both parameters demonstrated the capability for baseline-free crack detection, their e ff ectiveness was constrained by the strong dependence of the initial stage on sensor bonding conditions, which undermines the overall stability of the method. To overcome these limitations, this work introduced the root mean square (RMS) value of time-domain signals as a more stable and interpretable feature for online fatigue crack monitoring. Experimental results showed that the proposed RMS-based approach not only enables baseline-free detection of cracks smaller than 2 mm, but also maintains excellent stability throughout the entire fatigue process. In contrast to higher-order harmonic parameters, the RMS feature exhibits minimal sensitivity to bonding conditions, thereby ensuring more consistent and reliable detection performance. These findings establish a solid foundation for the development of a robust and practically applicable methodology for fatigue crack monitoring. Future work will focus on enhancing the generality and applicability of the proposed method by incorpo rating additional influencing factors. Specifically, the performance of the approach will be investigated under variable loading conditions, including changes in loading amplitude and loading ratio, and its sensitivity to di ff erent sensor placements beyond the centerline configuration will be evaluated. Furthermore, the e ff ect of environmental conditions, particularly temperature variations, will be systematically evaluated. Finally, vali dation on more complex structural configurations will be undertaken to explore the scalability of the method and its potential for real-world engineering applications. Conclusion

5. Acknowledgments

This work was supported by UKRI under the UK Government’s Horizon Europe Guarantee (grant agree ment No 101096073, AVATAR project.