BS-7706-1993.pdf
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1、BRITISH STANDARD Guide to Calibration and setting-up of the ultrasonic time of flight diffraction (TOFD) technique for the detection, location and sizing of flaws UDC 620.179.16.05:53.089.6 BS 7706 : 1993 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled C
2、opy Licensee=University of Hong Kong/5910986001 Not for Resale, 12/08/2006 04:46:34 MSTNo reproduction or networking permitted without license from IHS -,-,- BS 7706 : 1993 Amd. No. Date Committees responsible for this British Standard lkxt affected The preparation of this British Standard was entru
3、sted by the Welding Standards Policy Committee (WEE/-) to lkchnical Committee WEE/46, upon which the following bodies were represented: Aluminium Federation Associated Offices lkchnical Committee Association of Consulting Engineers BNF (Fulmer Materials Centre) British Airways British Chemical Engin
4、eering Contractors Association British Coal Corporation British Institute of Non-destructive lksting British Non-Ferrous Metals Federation British Railways Board British Steel Industry Department of Trade and Industry (Namas Executive) Electricity Association Health and Safety Executive Institute of
5、 Physics Institute of Quality Assurance Light Metal Founders Association Lloyds Register of Shipping Ministry of Defence National Radiological Protection Board Power Generation Contractors Association (BEAMA Ltd.) Railway Industry Association of Great Britain Royal Society of Chemistry Society of Br
6、itish Aerospace Companies Limited Society of Motor Manufacturers and Traders Limited Steel Casting Research and Trade Association Welding Institute This British Standard, having been prepared under the direction of the Welding Standards Policy Committee, was published under the authority of the Stan
7、dards Board and comes into effect on 15 December 1993 O BSI 1993 The following ES1 references relate to the work on this standard: Committee reference WEE/46 Draft for comment 92/81577 DC ISBN O 680 22311 6 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled
8、 Copy Licensee=University of Hong Kong/5910986001 Not for Resale, 12/08/2006 04:46:34 MSTNo reproduction or networking permitted without license from IHS -,-,- BS 7706 : 1993 Contents Committees responsible Foreword Inside front cover 2 Guide 1 Scope 2 References 3 Definitions 4 Principles of the me
9、thod 5 Equipment 6 7 Interpretation of the data 8 Setting-up procedures for flaw detection Estimation of flaw dimensions after flaw detection 3 4 4 5 8 10 17 19 9 Setting-up procedures for accurate flaw sizing 20 10 Confirmatory measurements 22 11 Accuracy of measurement 22 12 Training and qualifica
10、tion 24 Annexes A (informative) Special techniques based on TOFD 25 B (informative) Application of TOFD and reporting criteria 25 C (informative) Suggested steps towards the characterization of flaw echoes in TOFD 27 D (informative) Examples of typical scans 33 E (informative) Suggested framework fo
11、r training and qualification 35 Figures 1 2 3 D-scan (probe movement normal to beam) B-scan (probe movement in direction of beam) Diffraction from a crack-like flaw 3 3 6 4 Typical pattern of pulses from an internal flaw 7 5 Generalized two probe testing geometry 8 6 Calibration block for TOFD using
12、 V notch or electrodischarge machined slit 14 7 Gain setting using grain noise 16 List of references Inside back cover 1 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=University of Hong Kong/5910986001 Not for Resale, 12/08/2006 04:46:34
13、MSTNo reproduction or networking permitted without license from IHS -,-,- BS 7706 : 1993 Foreword This British Standard has been prepared under the direction of the Welding Standards Policy Committee. It supersedes DD 174 : 1988, which is withdrawn. This revision incorporates updated guidance which
14、has resulted from the increased application of the ultrasonic time of fight diffraction technique (TOFD) in industry. The TOFD technique was originaiiy developed at the National Non-destructive %sting Centre at Harwell and has since seen application in a variety of industries. The primary objective
15、of this British Standard is to facilitate the wide implementation of this relatively new non-destructive testing technology in industry. It is envisaged that this British Standard will in due course be superseded by standards that w i l l detail the methods for TOFD technique examination for specifi
16、c applications. This British Standard provides guidance on the application of TOFD technique for the detection, location and sizing of flaws in materials. It may be expanded to cover other important applications of TOFD. It is most important to bear in mind that echo amplitude is not used quantitati
17、vely by this technique for the determination of flaw size. The conventional amplitude-based flaw sizing associated with ultrasonics is thus largely invalid when this technique is used although it may be used for further discrimination. The echo amplitude is only employed in TOFD measurements in conn
18、ection with three tasks. (a) Where the pulses from the flaws being sought have to be resolvable against the local noise background, for instance the ultrasonic grain scatter. l ensure that this is the case (or to place limits on the validity of a particular measurement) the known or experimentally d
19、etermined variation of pulse amplitude as a function of range, position in the ultrasonic beam, etc. may be invoked. (b) Where the relative amplitudes of echoes from the top and bottom extremities of flaws may provide important clues about the character of the flaw. (c) Where the amplitude of the pu
20、lse from an artificial flaw can be used to confirm that system calibration has not changed during a measurement or from measurement to measurement. The use of TOFD should be considered in any inspection task requiring rapid and reliable flaw detection coupled with an accurate assessment of flaw size
21、. It can be adapted to many test geometries with little difficulty but special instructions and equipment may be needed for the inspection of complex geometries such as nodes or nozzles. Care should also be taken if the technique is considered for use on coarse-grained or ultrasonically difficult ma
22、terials. It is recognized that equipment suitable for carrying out the TOFD technique is not yet widely available and this British Standard, which is written in sufficiently general terms to be applicable to the types of equipment currently known to be employed for TOFD, describes the nature of the
23、equipment required and also its calibration. It is assumed in the drafting of this British Standard that the execution of its provisions is entrusted to appropriately qualified and experienced non-destructive testing personnel. Compliance with a British Standard does not of itself confer immunity fr
24、om legai obligations. 2 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=University of Hong Kong/5910986001 Not for Resale, 12/08/2006 04:46:34 MSTNo reproduction or networking permitted without license from IHS -,-,- BS 7706 : 1993 Directio
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