37:
28:
19:
105:
One of the limitations of TOFD is the "dead zone' created by the lateral wave signal just below the inspection surface (or OD surface in case of the pipe). The dead zone is approximately 5 mm and there is no flaw detection in this zone. Calibration blocks with side drilled holes as shown in
Reference
84:
sits on opposite sides of a weld. One of the probes, the transmitter, emits an ultrasonic pulse that is picked up by the probe on the other side, the receiver. In undamaged pipes, the signals picked up by the receiver probe are from two waves: one that travels along the surface and one that reflects
59:
of welds for defects. TOFD originated from tip diffraction techniques which were first published by Silk and
Liddington in 1975 which paved the way for TOFD. Later works on this technique are given in a number of sources which include Harumi et al. (1989), Avioli et al. (1991), and Bray and Stanley
76:
Measuring the amplitude of reflected signal is a relatively unreliable method of sizing defects because the amplitude strongly depends on the orientation of the crack. Instead of amplitude, TOFD uses the time of flight of an ultrasonic pulse to determine the position and size of a reflector.
63:
Bray and
Stanley (1997) summarized TOFD as tip-diffraction techniques which utilized the principle that the tips of a crack when struck by a wave will diffract the signals back to the other location on the surface. The depth of these tips can be determined from the diffracted energy.
22:
A TOFD setup with transmit and receive probes. In this case the receive probe sees four indications: one from the lateral wave that has travelled along the upper surface, one from the wave that has reflected off the far surface, and two from the defect in the test
31:
Typical TOFD data, created by aligning the data traces from the above figure vertically and colour-coding them for amplitude. The defect or discontinuity creates a characteristic parabolic indication, due to the apparent change in depth as the probes
67:
TOFD was invented in the UK in the 1970s initially as a research tool. The use of TOFD enabled crack sizes to be measured more accurately, so that expensive components could be kept in operation as long as possible with minimal risk of failure.
128:
TOFD has a dead zone where it is not sensitive to defects, hence TOFD ought always to be supplemented by a conventional pulse-echo examination or phased array. The pulse echo probes are commonly mounted on the same buggy as the TOFD
89:
of the ultrasonic wave from the tip(s) of the crack. Using the measured time of flight of the pulse, the depth of a crack tips can be calculated automatically by simple trigonometry.
273:
295:
321:
Non-destructive testing – Ultrasonic examination – Part 6: Time-of-flight diffraction technique as a method for detection and sizing of discontinuities
338:
Engineering
Applications of Ultrasonic Time-of-Flight Diffraction, 2nd ed., J. P. Charlesworth and J. A. G. Temple, Research Studies Press, 2002.
311:
229:
202:
257:
375:
150:
M.G. Silk, B.H. Lidington (1975). "The potential of scattered or diffracted ultrasound in the determination of crack depth".
125:
Compared to conventional methods of ultrasonic testing, TOFD is sensitive to cracks and measures their dimensions accurately.
56:
250:
Nondestructive
Testing Vol 3.03, Standard Practice for Use of Time of Flight Diffraction (TOFD) Technique
327:
Non-destructive testing of welds – Time-of-flight diffraction technique (TOFD) – Acceptance levels
267:
52:
253:
225:
198:
167:
190:
159:
81:
36:
116:
348:
187:
Ultrasonic
Nondestructive Evaluation Engineering and Biological Material Characterization
252:. West Conshohocken, PA: American Society for Testing of Materials. pp. 1251–62.
219:
369:
349:
TOFD: – An
Alternate Non-Destructive Testing Procedure to Replace Traditional Methods
305:
Welding – Use of time-of-flight diffraction technique (TOFD) for examination of welds
163:
122:
Probes are mounted on a buggy that travels along a weld, recording data as it moves.
359:
185:
Bray, Don (2003). "Ultrasonic
Systems for Industrial Nondestructive Evaluation".
221:
Engineering
Applications of Ultrasonic Time-of-Flight Diffraction Second Edition
86:
194:
171:
97:
Phased Array + TOFD combination is commonly used to inspect pipeline welds.
27:
18:
353:
106:
and ISO 10863 used to validate the "dead zone" and sizing accuracy.
35:
26:
17:
132:
Requires ultrasound technicians with advanced training.
85:
off the far wall. When a crack is present, there is a
356:returns over 500 hits for the search term 'TOFD'
296:International Organization for Standardization
8:
218:J. P. Charlesworth, J. A. G. Temple (2001).
272:: CS1 maint: numeric names: authors list (
224:. Research Studies Press LTD. p. 254.
55:is a sensitive and accurate method for the
115:A computerised and automated system for
142:
312:European Committee for Standardization
265:
7:
243:
241:
14:
1:
164:10.1016/0029-1021(75)90024-9
80:In a TOFD system, a pair of
40:Manually-guided TOFD probes
392:
45:Time-of-flight diffraction
195:10.1201/9780203501962.ch3
354:NDT.net Database Search
152:Non-Destructive Testing
376:Nondestructive testing
72:Principle of operation
57:nondestructive testing
41:
33:
24:
39:
30:
21:
248:ASTM, E2373 (2012).
303:ISO/DIS 10863:11,
53:ultrasonic testing
42:
34:
25:
231:978-0-86380-239-3
204:978-0-8493-1462-9
82:ultrasonic probes
383:
278:
277:
271:
263:
245:
236:
235:
215:
209:
208:
182:
176:
175:
147:
391:
390:
386:
385:
384:
382:
381:
380:
366:
365:
360:TOFD Principles
345:
335:
292:
287:
285:Further reading
282:
281:
264:
260:
247:
246:
239:
232:
217:
216:
212:
205:
184:
183:
179:
149:
148:
144:
139:
117:weld inspection
112:
103:
95:
74:
12:
11:
5:
389:
387:
379:
378:
368:
367:
364:
363:
357:
351:
344:
343:External links
341:
340:
339:
334:
331:
330:
329:
323:
316:
315:
308:
307:
300:
299:
291:
288:
286:
283:
280:
279:
258:
237:
230:
210:
203:
177:
158:(3): 146–151.
141:
140:
138:
135:
134:
133:
130:
126:
123:
120:
111:
108:
102:
99:
94:
91:
73:
70:
13:
10:
9:
6:
4:
3:
2:
388:
377:
374:
373:
371:
361:
358:
355:
352:
350:
347:
346:
342:
337:
336:
333:Other sources
332:
328:
324:
322:
318:
317:
313:
310:
309:
306:
302:
301:
297:
294:
293:
289:
284:
275:
269:
261:
259:9780803187290
255:
251:
244:
242:
238:
233:
227:
223:
222:
214:
211:
206:
200:
196:
192:
188:
181:
178:
173:
169:
165:
161:
157:
153:
146:
143:
136:
131:
127:
124:
121:
118:
114:
113:
109:
107:
100:
98:
92:
90:
88:
83:
78:
71:
69:
65:
61:
58:
54:
50:
46:
38:
29:
20:
16:
326:
320:
304:
249:
220:
213:
186:
180:
155:
151:
145:
104:
96:
93:Applications
79:
75:
66:
62:
51:) method of
48:
44:
43:
15:
101:Reliability
87:diffraction
362:on NDT.net
325:EN 15617,
319:EN 583-6,
137:References
290:Standards
268:cite book
172:0029-1021
370:Category
110:Features
60:(1997).
129:probes.
32:travel.
23:object.
256:
228:
201:
170:
314:(CEN)
298:(ISO)
274:link
254:ISBN
226:ISBN
199:ISBN
168:ISSN
49:TOFD
191:doi
160:doi
372::
270:}}
266:{{
240:^
197:.
189:.
166:.
154:.
276:)
262:.
234:.
207:.
193::
174:.
162::
156:8
119:.
47:(
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
