Monitoring fatigue crack growth using nonlinear ultrasonic phased array imaging

Jingwei Cheng, Jack Potter, Anthony Croxford, Bruce Drinkwater

Research output: Contribution to journalArticle (Academic Journal)peer-review

34 Citations (Scopus)
437 Downloads (Pure)


Nonlinear imaging techniques have recently emerged which have the potential to detect material degradation and challenging defects, such as closed cracks. This paper describes an investigation into the performance of Nonlinear Ultrasonic Imaging (NUI) for the monitoring of the early stages of fatigue crack growth. This technique, in conjunction with conventional array imaging, is applied to the periodic monitoring of steel compact tension specimens subjected to high cycle fatigue loading. The detection limits of these techniques are investigated. Their abilities to localize and detect small cracks are further quantified with the aid of micrography. The results suggest that NUI is more sensitive than conventional ultrasonic imaging to the microscale changes occurring at the early stages of failure, i.e. detectability starts c. 15% of fatigue life. In addition to early detection, the potential for NUI to deliver accurate sizing of fatigue cracks and monitor crack propagation is also presented.
Original languageEnglish
Article number055006
Number of pages10
JournalSmart Materials and Structures
Issue number5
Early online date17 Mar 2017
Publication statusPublished - May 2017


  • monitoring
  • fatigue crack
  • ultrasonic phased array
  • nonlinear imaging


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