Sizing limitations of ultrasonic array images for non-sharp defects and their impact on structural integrity assessments

Shivaprasad Shridhara Bhat; Jie Zhang; Nicolas Larrosa

doi:10.1016/j.tafmec.2022.103625

Sizing limitations of ultrasonic array images for non-sharp defects and their impact on structural integrity assessments

Shivaprasad Shridhara Bhat^*, Jie Zhang, Nicolas Larrosa

^*Corresponding author for this work

Research output: Contribution to journal › Article (Academic Journal) › peer-review

3 Citations (Scopus)

Abstract

Existing structural integrity assessment procedures typically assume flaws to be infinitely sharp when they cannot be considered as local thinned areas. This assumption is often over-conservative, resulting in a pessimistic assessment of structural components and a significant underestimation of their margins of safety against fracture. One of the main challenges while adopting non-destructive evaluation techniques is distinguishing between sharp cracks (e.g., fatigue) and non-sharp defects and identifying the more severe ones. Towards this broader challenge, the present work aims to examine the sizing limitation and accuracy of ultrasonic array image-based techniques for non-sharp defects (surface breaking u-notches) and investigate how these measurements would affect the structural integrity assessment of components. Parametric numerical simulations and experimental measurements are performed to generate full-matrix capture datasets, which are then processed using the total focusing method to form an image. The image-based sizing approach is shown to perform efficiently for notch depths higher than the inspection wavelength (λ_L), i.e. as small as 0.2 mm, and semi-notch widths as small as 0.1 mm. The influence of ultrasonic measurements on structural integrity assessments is highlighted using different case studies in the context of non-sharp defects of fatigue and fracture strength estimates. For the cases under analysis, resolving non-sharp defects led up to 5× and 3× values of effective fracture toughness and fatigue strength, respectively. We have also seen that a 30 % uncertainty in semi-notch width sizing would result in a 30 % and 20 % error in fatigue strength and fracture toughness estimations, respectively.

Original language	English
Article number	103625
Number of pages	13
Journal	Theoretical and Applied Fracture Mechanics
Volume	122
Early online date	17 Oct 2022
DOIs	https://doi.org/10.1016/j.tafmec.2022.103625
Publication status	Published - 1 Dec 2022

Bibliographical note

Funding Information:
The authors would also like to thank the UK Engineering and Physical Sciences Research Council (EPSRC) for its financial support through grant number EP/S012362/1. The lead author would like to thank the Advanced Computing Research Centre (ACRC) at the University of Bristol ( www.bristol.ac.uk/acrc ) for providing access to the Blue Crystal 4 & Blue Pebble GPU clusters for performing numerical simulations. The authors would also like to thank Jose Antonio Balbin (University of Sevila, Spain) & Greg Thorwald (Quest Integrity USA LLC) for sharing the raw data presented as part of the case studies in Section 5 .

Funding Information:
The authors would also like to thank the UK Engineering and Physical Sciences Research Council (EPSRC) for its financial support through grant number EP/S012362/1. The lead author would like to thank the Advanced Computing Research Centre (ACRC) at the University of Bristol (www.bristol.ac.uk/acrc) for providing access to the Blue Crystal 4 & Blue Pebble GPU clusters for performing numerical simulations. The authors would also like to thank Jose Antonio Balbin (University of Sevila, Spain) & Greg Thorwald (Quest Integrity USA LLC) for sharing the raw data presented as part of the case studies in Section 5.

Publisher Copyright:
© 2022 The Author(s)

Keywords

Defect sizing
Full-matrix capture
Notch fracture mechanics
Structural integrity assessment
Total focusing method

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title = "Sizing limitations of ultrasonic array images for non-sharp defects and their impact on structural integrity assessments",

abstract = "Existing structural integrity assessment procedures typically assume flaws to be infinitely sharp when they cannot be considered as local thinned areas. This assumption is often over-conservative, resulting in a pessimistic assessment of structural components and a significant underestimation of their margins of safety against fracture. One of the main challenges while adopting non-destructive evaluation techniques is distinguishing between sharp cracks (e.g., fatigue) and non-sharp defects and identifying the more severe ones. Towards this broader challenge, the present work aims to examine the sizing limitation and accuracy of ultrasonic array image-based techniques for non-sharp defects (surface breaking u-notches) and investigate how these measurements would affect the structural integrity assessment of components. Parametric numerical simulations and experimental measurements are performed to generate full-matrix capture datasets, which are then processed using the total focusing method to form an image. The image-based sizing approach is shown to perform efficiently for notch depths higher than the inspection wavelength (λL), i.e. as small as 0.2 mm, and semi-notch widths as small as 0.1 mm. The influence of ultrasonic measurements on structural integrity assessments is highlighted using different case studies in the context of non-sharp defects of fatigue and fracture strength estimates. For the cases under analysis, resolving non-sharp defects led up to 5× and 3× values of effective fracture toughness and fatigue strength, respectively. We have also seen that a 30 % uncertainty in semi-notch width sizing would result in a 30 % and 20 % error in fatigue strength and fracture toughness estimations, respectively.",

keywords = "Defect sizing, Full-matrix capture, Notch fracture mechanics, Structural integrity assessment, Total focusing method",

author = "Bhat, {Shivaprasad Shridhara} and Jie Zhang and Nicolas Larrosa",

note = "Funding Information: The authors would also like to thank the UK Engineering and Physical Sciences Research Council (EPSRC) for its financial support through grant number EP/S012362/1. The lead author would like to thank the Advanced Computing Research Centre (ACRC) at the University of Bristol ( www.bristol.ac.uk/acrc ) for providing access to the Blue Crystal 4 & Blue Pebble GPU clusters for performing numerical simulations. The authors would also like to thank Jose Antonio Balbin (University of Sevila, Spain) & Greg Thorwald (Quest Integrity USA LLC) for sharing the raw data presented as part of the case studies in Section 5 . Funding Information: The authors would also like to thank the UK Engineering and Physical Sciences Research Council (EPSRC) for its financial support through grant number EP/S012362/1. The lead author would like to thank the Advanced Computing Research Centre (ACRC) at the University of Bristol (www.bristol.ac.uk/acrc) for providing access to the Blue Crystal 4 & Blue Pebble GPU clusters for performing numerical simulations. The authors would also like to thank Jose Antonio Balbin (University of Sevila, Spain) & Greg Thorwald (Quest Integrity USA LLC) for sharing the raw data presented as part of the case studies in Section 5. Publisher Copyright: {\textcopyright} 2022 The Author(s)",

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N2 - Existing structural integrity assessment procedures typically assume flaws to be infinitely sharp when they cannot be considered as local thinned areas. This assumption is often over-conservative, resulting in a pessimistic assessment of structural components and a significant underestimation of their margins of safety against fracture. One of the main challenges while adopting non-destructive evaluation techniques is distinguishing between sharp cracks (e.g., fatigue) and non-sharp defects and identifying the more severe ones. Towards this broader challenge, the present work aims to examine the sizing limitation and accuracy of ultrasonic array image-based techniques for non-sharp defects (surface breaking u-notches) and investigate how these measurements would affect the structural integrity assessment of components. Parametric numerical simulations and experimental measurements are performed to generate full-matrix capture datasets, which are then processed using the total focusing method to form an image. The image-based sizing approach is shown to perform efficiently for notch depths higher than the inspection wavelength (λL), i.e. as small as 0.2 mm, and semi-notch widths as small as 0.1 mm. The influence of ultrasonic measurements on structural integrity assessments is highlighted using different case studies in the context of non-sharp defects of fatigue and fracture strength estimates. For the cases under analysis, resolving non-sharp defects led up to 5× and 3× values of effective fracture toughness and fatigue strength, respectively. We have also seen that a 30 % uncertainty in semi-notch width sizing would result in a 30 % and 20 % error in fatigue strength and fracture toughness estimations, respectively.

AB - Existing structural integrity assessment procedures typically assume flaws to be infinitely sharp when they cannot be considered as local thinned areas. This assumption is often over-conservative, resulting in a pessimistic assessment of structural components and a significant underestimation of their margins of safety against fracture. One of the main challenges while adopting non-destructive evaluation techniques is distinguishing between sharp cracks (e.g., fatigue) and non-sharp defects and identifying the more severe ones. Towards this broader challenge, the present work aims to examine the sizing limitation and accuracy of ultrasonic array image-based techniques for non-sharp defects (surface breaking u-notches) and investigate how these measurements would affect the structural integrity assessment of components. Parametric numerical simulations and experimental measurements are performed to generate full-matrix capture datasets, which are then processed using the total focusing method to form an image. The image-based sizing approach is shown to perform efficiently for notch depths higher than the inspection wavelength (λL), i.e. as small as 0.2 mm, and semi-notch widths as small as 0.1 mm. The influence of ultrasonic measurements on structural integrity assessments is highlighted using different case studies in the context of non-sharp defects of fatigue and fracture strength estimates. For the cases under analysis, resolving non-sharp defects led up to 5× and 3× values of effective fracture toughness and fatigue strength, respectively. We have also seen that a 30 % uncertainty in semi-notch width sizing would result in a 30 % and 20 % error in fatigue strength and fracture toughness estimations, respectively.

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DO - 10.1016/j.tafmec.2022.103625

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ER -

Sizing limitations of ultrasonic array images for non-sharp defects and their impact on structural integrity assessments

Abstract

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Keywords

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