Engineering applications of ultrasonic time-of-flight diffraction

$Cover image for Engineering applications of ultrasonic time-of-flight diffraction$

Title:

Personal Author:

Charlesworth, J. P.

Series:

Ultrasonic inspection in engineering series ; 2

Edition:

2nd ed.

Publication Information:

Baldock, Hertfordshire : Research Studies Press, 2001

ISBN:

9780863802393

Subject Term:

Ultrasonic testing

Added Author:

Temple, J. A. G.

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Library	Item Barcode	Call Number	Material Type	Item Category 1	Status
Searching... PSZ JB	30000004811042	TA417.4 C47 2001	Open Access Book	Book	Searching... Unknown
Searching... PSZ KL	30000004811083	TA417.4 C47 2001	Open Access Book	Book	Searching... Unknown

The ultrasonic time of flight diffraction technique (TOFD) is a routine method for defect detection and sizing performance in engineering structures. The first book by the authors, published in 1989, aimed to give the non-destructive testing engineer comprehensive information on the theoretical background, practicl implementation and performance of the technique. The method is now widely used and is a European as well as a British Standard. This second edition includes new material on the theoretical basis, experimental demonstration of capability and engineering applications of TOFD. The book also includes a chapter on standards, citing work on British and European standards.

List of Tables	p. xvii
List of Figures	p. xix
1 Introduction	p. 1
1.1 The need for accurate measurement of defect size	p. 2
1.2 History of Time-of-Flight Diffraction	p. 3
1.2.1 Conventional ultrasonic testing	p. 4
1.2.2 The problems with pulse-echo techniques	p. 4
1.2.3 The diffraction process	p. 5
1.2.4 The basic Time-of-Flight Diffraction technique	p. 6
1.3 Development of experimental techniques for Time-of-Flight Diffraction	p. 7
1.3.1 The first digital gauge	p. 8
1.3.2 The B-scan display	p. 8
1.3.3 Digital signal processing	p. 9
1.3.4 First application to thick-section steel	p. 10
1.4 Outline of the remainder of the book	p. 11
2 Theoretical Basis of Time-of-Flight Diffraction	p. 15
2.1 Waves in homogeneous and isotropic media	p. 15
2.1.1 Wavespeeds in terms of elastic constants	p. 16
2.1.2 Other wave motions in isotropic media	p. 18
2.2 Diffraction of waves	p. 18
2.2.1 Diffraction of plane elastic waves by infinite straight crack edges	p. 19
2.3 Time-of-Flight Diffraction in Isotropic Media	p. 20
2.3.1 Through-wall size and depth of cracks	p. 22
2.3.2 Accuracy of through-wall size measurements	p. 25
2.3.2.1 Probe shoe effects	p. 25
2.3.2.2 Probe separation errors	p. 28
2.3.2.3 Coupling film thickness	p. 29
2.3.2.4 Variations in velocity	p. 31
2.3.2.5 Inspection surface characteristics	p. 32
2.3.2.6 Effect of time resolution on depth resolution	p. 32
2.3.2.7 Effect of timing accuracy	p. 34
2.3.3 Locus of estimated crack through-wall size or depth	p. 37
2.3.4 Diffraction arcs	p. 38
2.4 Alternative Methods of Crack Depth Estimation	p. 42
2.5 Single probe techniques	p. 44
2.5.1 Satellite Pulse Techniques and SLIC transducer modules	p. 47
2.5.2 ALOK evaluation of time-of-flight data	p. 49
3 Signal Amplitudes and Comparison with other Techniques	p. 51
3.1 Time-of-Flight Diffraction signals from smooth flat cracks	p. 52
3.1.1 Optimum beam angles	p. 52
3.1.2 Magnitude and variation of diffracted signal amplitudes	p. 53
3.1.3 Calibration reflector	p. 60
3.2 Signal amplitudes compared with those generated by other techniques	p. 61
3.2.1 The defects	p. 61
3.2.2 The transducer scans	p. 62
3.2.3 The calibration signals	p. 62
3.2.4 Resolution of diffracted signals in pulse-echo	p. 62
3.2.5 Pulse-echo inspection of ribbon and circular cracks	p. 64
3.2.6 Time-of-Flight Diffraction signals for ribbon and circular defects	p. 66
3.3 Time-of-Flight Diffraction signals from skewed, planar cracks	p. 69
4 Design of Time-of-Flight Diffraction Equipment for Simple Geometries	p. 71
4.1 Coverage design for buried defects	p. 71
4.1.1 Choice of frequency	p. 72
4.1.2 Arrangement of probes	p. 72
4.1.2.1 Coverage from a single probe pair	p. 72
4.1.2.2 Probe arrangement for DDT Plates 1 and 2	p. 75
4.1.3 Scanning arrangements	p. 77
4.1.4 Transverse defects	p. 77
4.2 Near-surface defects	p. 78
4.2.1 Probe arrangement	p. 78
4.2.2 Scanning technique	p. 79
4.3 Data acquisition system	p. 80
4.3.1 The DDT instrumentation system	p. 80
4.4 Signal Averaging	p. 81
4.5 Recent developments in instrumentation	p. 82
5 Processing, Display and Analysis of Time-of-Flight Data	p. 85
5.1 Simple forms of display	p. 85
5.2 Two-dimensional displays	p. 86
5.2.1 Line drawing displays	p. 86
5.2.2 Grey scale and colour displays	p. 87
5.2.2.1 Analogue displays	p. 87
5.2.2.2 Digital displays	p. 88
5.2.3 Hardcopy output	p. 88
5.2.4 Storage and exchange of raw and analysed data	p. 89
5.3 Analysis of A-scan data	p. 90
5.4 Data flattening	p. 90
5.5 Signal recognition	p. 93
5.5.1 Arcs and curve fitting	p. 93
5.6 Measurement of defect location	p. 97
5.6.1 Depth from the inspection surface	p. 97
5.6.2 Position along the scan line	p. 97
5.6.3 Lateral position	p. 98
5.7 Measurement of defect length	p. 98
5.7.1 Using the shaped cursor for defect length measurement	p. 98
5.7.2 Effects of defect shape on apparent defect length	p. 99
5.8 Signal Processing	p. 102
5.8.1 Processing techniques for improving the accuracy of defect length measurement	p. 102
5.8.2 Derivation of signal phase	p. 104
5.8.3 Other signal processing methods	p. 104
5.9 Defect characterisation	p. 104
5.10 Modelling studies on analysis of TOFD data	p. 105
6 Complex Geometries	p. 107
6.1 T-butt welds	p. 107
6.2 Inspection requirements for offshore structures	p. 109
6.3 Application to offshore structures	p. 110
6.4 Signal acquisition and analysis	p. 111
6.5 Results of trials	p. 113
6.6 PWR nozzles	p. 117
6.7 Recent developments in nozzle inspection	p. 124
7 Additional Complexities	p. 127
7.1 Anisotropic media	p. 128
7.1.1 Austenitic cladding	p. 129
7.1.2 Anisotropic cladding model	p. 129
7.1.3 Transit times	p. 131
7.1.4 The reference path	p. 134
7.1.5 Experimental confirmation of the model	p. 134
7.1.6 Austenitic steel	p. 137
7.1.7 Diffraction in anisotropic materials	p. 138
7.2 Compressive stress	p. 139
7.2.1 Experimental and theoretical results	p. 140
7.2.2 Application to Time-of-Flight Diffraction	p. 140
7.3 Component curvature	p. 145
8 Experimental Demonstrations of Capability	p. 147
8.1 Limitations of test-block exercises	p. 148
8.1.1 The number of defects	p. 148
8.1.2 Comparison with destructive tests	p. 149
8.2 Round-robin trials	p. 150
8.3 Results obtained in the Welding Institute collaborative programme	p. 151
8.3.1 Phase 1	p. 151
8.3.2 Phase 2	p. 152
8.4 UKAEA Defect Detection Trials (DDT)	p. 153
8.4.1 Caveats concerning the Defect Detection Trials	p. 155
8.4.2 A comment on automated inspections and Time-of-Flight Diffraction	p. 155
8.4.3 Sizing capability	p. 156
8.4.4 Summary of results from the Defect Detection Trials	p. 156
8.4.5 Results obtained for through-wall size	p. 157
8.4.6 Errors in TOFD through-wall sizing for Plates 1 and 2	p. 157
8.4.7 Typical data display from the Defect Detection Trials	p. 160
8.4.8 Characterisation of defects	p. 161
8.4.9 Results for Plates 3 and 4	p. 164
8.5 The PISC II programme	p. 164
8.6 The PISC III Programme	p. 166
8.6.1 PISC III Action 3--Nozzles and dissimialr metal welds	p. 168
8.6.2 PISC III Action 4--Austenitic welds	p. 171
8.7 Comparison of TOFD with radiographic inspection	p. 175
8.8 Sizing accuracy of TOFD compared with amplitude based techniques	p. 176
8.9 Implications for structural integrity	p. 177
9 Applications of Time-of-Flight Diffraction	p. 181
9.1 Water-cooled nuclear pressure vessels and nozzles	p. 181
9.2 Gas-cooled nuclear pressure vessels	p. 182
9.3 Other nuclear components	p. 183
9.4 Non-nuclear pressure vessels	p. 183
9.5 Turbine and generator components	p. 183
9.6 Offshore structures	p. 185
9.7 General weld inspection and plant monitoring	p. 186
9.8 Monitoring defect growth	p. 186
9.9 Inspection of steel bridges	p. 187
9.10 Other applications of TOFD	p. 188
9.11 Future potential	p. 188
10 Application of Codes and Standards to TOFD Inspection	p. 191
10.1 Types of standard	p. 191
10.2 Development of standards for TOFD	p. 192
10.3 Current standards specific to TOFD	p. 195
10.3.1 British Standard BS7706:1993	p. 195
10.3.2 European Standard ENV 583-6	p. 195
10.4 Inspection qualification	p. 196
10.5 Qualification of TOFD	p. 198
10.6 Coda	p. 198
Appendix	p. 199
A.1 Helmholtz potentials	p. 199
A.2 Other wave motions in isotropic media	p. 199
A.3 Geometrical theory of diffraction	p. 200
A.3.1 Diffraction by curved edges	p. 201
A.3.2 Incident potential	p. 202
A.3.3 Calibration reflector	p. 203
A.4 Diffraction of plane elastic waves by straight crack edges of infinite extent	p. 204
A.5 Pulse shape from a piston source	p. 207
A.6 Signal averaging	p. 210
A.7 Defect characterisation	p. 213
A.8 Transversely isotropic media	p. 213
A.9 Component curvature	p. 215
A.10 Confidence levels in test-block exercises	p. 217
A.11 Distribution of sizing errors	p. 218
A.12 Implications for structural integrity	p. 219
Bibliography	p. 223
Index	p. 245

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