Dynamic characterisation of ductile damage evolution in PE pipes via ultrasonic structural health monitoring

Polyethylene (PE) pipelines are critical for gas transportation, but long-term service leads to wall deterioration, leading to stress concentration and subsequent ductile failure. Ultrasonic testing is effective formaterial and structural damage monitoring. However, current approaches exhibit limited capability for monitoring damage evolution in PE pipes. This study proposes an ultrasonic-based structural health monitoring framework to characterise the ductile failure of PE pipes under high hoop stresses. Online ultrasonic measurement was implemented during accelerated ageing tests using water-coupled transducers to capture real-time degradation processes. Two damage indices – the Energy-Based Damage Index (EDI) and Nonlinear Signal Difference Coefficient (NSDC) – were extracted from ultrasonic echo signals on the back wall of the pipes. The Criteria Importance Through Intercriteria Correlation (CRITIC) weighting method was employed to integrate them into a Comprehensive Damage Index (CDI). Experimental results demonstrate that both EDI and NSDC exhibit sensitivity to ductile damage evolution in PE pipes, effectively monitoring wall damage. The CDI achieves more comprehensive damage characterisation by accounting for ultrasonic energy attenuation and waveform distortion induced by material deterioration. The proposed framework provides a validated methodology for monitoring of ductile damage in PE pipes, bridging the gap between static defect identification and dynamic condition assessment.