### Abstract

Ultrasonic phased array systems are becoming increasingly popular as tools for the nondestructive evaluation of safety-critical structures. The data captured by these arrays can be analysed to extract information on the existence, location and shape of defects. However, many of the existing imaging algorithms currently used for this purpose are heavily reliant on the choice of threshold at which the defect measurements are made and this aspect of subjectivity can lead to varying defect characterisations between different operators. To combat this, the work presented here uses the Born approximation to derive a mathematical expression for the crack size given the width of the pulse-echo response lobe of the frequency domain scattering matrix. These scattering matrices can be easily extracted from experimental data if the location of the flaw is known a priori and so the method has been developed exclusively for the objective characterisation of flaws. Due to the analytical nature of this work, conclusions can be drawn on the formula's sensitivity to various experimental parameters and these are corroborated using synthetic data. The sizing of a subwavelength crack is undertaken and it is shown that examination of the scattering matrix correctly captures the crack form of the defect and outperforms the standard TFM in this regard (the nature of the defect is obscured by side lobes in the TFM image). It is also suggested that the derived formulae could potentially be used to inform and optimise array design.

Original language | English |
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Title of host publication | 54th Annual British Conference of Non-Destructive Testing, NDT 2015 |

Place of Publication | Northampton |

Pages | 282-291 |

Number of pages | 10 |

Publication status | Published - 8 Sep 2015 |

Event | 54th Annual British Conference of Non-Destructive Testing, NDT 2015 - International Centre, Telford, United Kingdom Duration: 8 Sep 2015 → 10 Sep 2015 |

### Conference

Conference | 54th Annual British Conference of Non-Destructive Testing, NDT 2015 |
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Country | United Kingdom |

City | Telford |

Period | 8/09/15 → 10/09/15 |

### Fingerprint

### Keywords

- bridge decks
- cracks
- defects
- frequency domain analysis
- matrix algebra
- nondestructive examination
- ultrasonic transducers
- analytical approach
- critical structures
- experimental parameters
- extract informations
- matheematical expressions
- non destructive evaluation
- ultrasonic phased array systems

### Cite this

*54th Annual British Conference of Non-Destructive Testing, NDT 2015*(pp. 282-291). Northampton.

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*54th Annual British Conference of Non-Destructive Testing, NDT 2015.*Northampton, pp. 282-291, 54th Annual British Conference of Non-Destructive Testing, NDT 2015, Telford, United Kingdom, 8/09/15.

**An analytical approach to objectively sizing cracks using ultrasonic phased array data.** / Tant, Katherine M M; Mulholland, Anthony J.; Gachagan, Anthony.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution book

TY - GEN

T1 - An analytical approach to objectively sizing cracks using ultrasonic phased array data

AU - Tant, Katherine M M

AU - Mulholland, Anthony J.

AU - Gachagan, Anthony

PY - 2015/9/8

Y1 - 2015/9/8

N2 - Ultrasonic phased array systems are becoming increasingly popular as tools for the nondestructive evaluation of safety-critical structures. The data captured by these arrays can be analysed to extract information on the existence, location and shape of defects. However, many of the existing imaging algorithms currently used for this purpose are heavily reliant on the choice of threshold at which the defect measurements are made and this aspect of subjectivity can lead to varying defect characterisations between different operators. To combat this, the work presented here uses the Born approximation to derive a mathematical expression for the crack size given the width of the pulse-echo response lobe of the frequency domain scattering matrix. These scattering matrices can be easily extracted from experimental data if the location of the flaw is known a priori and so the method has been developed exclusively for the objective characterisation of flaws. Due to the analytical nature of this work, conclusions can be drawn on the formula's sensitivity to various experimental parameters and these are corroborated using synthetic data. The sizing of a subwavelength crack is undertaken and it is shown that examination of the scattering matrix correctly captures the crack form of the defect and outperforms the standard TFM in this regard (the nature of the defect is obscured by side lobes in the TFM image). It is also suggested that the derived formulae could potentially be used to inform and optimise array design.

AB - Ultrasonic phased array systems are becoming increasingly popular as tools for the nondestructive evaluation of safety-critical structures. The data captured by these arrays can be analysed to extract information on the existence, location and shape of defects. However, many of the existing imaging algorithms currently used for this purpose are heavily reliant on the choice of threshold at which the defect measurements are made and this aspect of subjectivity can lead to varying defect characterisations between different operators. To combat this, the work presented here uses the Born approximation to derive a mathematical expression for the crack size given the width of the pulse-echo response lobe of the frequency domain scattering matrix. These scattering matrices can be easily extracted from experimental data if the location of the flaw is known a priori and so the method has been developed exclusively for the objective characterisation of flaws. Due to the analytical nature of this work, conclusions can be drawn on the formula's sensitivity to various experimental parameters and these are corroborated using synthetic data. The sizing of a subwavelength crack is undertaken and it is shown that examination of the scattering matrix correctly captures the crack form of the defect and outperforms the standard TFM in this regard (the nature of the defect is obscured by side lobes in the TFM image). It is also suggested that the derived formulae could potentially be used to inform and optimise array design.

KW - bridge decks

KW - cracks

KW - defects

KW - frequency domain analysis

KW - matrix algebra

KW - nondestructive examination

KW - ultrasonic transducers

KW - analytical approach

KW - critical structures

KW - experimental parameters

KW - extract informations

KW - matheematical expressions

KW - non destructive evaluation

KW - ultrasonic phased array systems

UR - http://www.scopus.com/inward/record.url?scp=84953774757&partnerID=8YFLogxK

UR - http://www.bindt.org/events/NDT-2015/

M3 - Conference contribution book

SN - 9781510813236

SP - 282

EP - 291

BT - 54th Annual British Conference of Non-Destructive Testing, NDT 2015

CY - Northampton

ER -