1、June 2014Translation by DIN-Sprachendienst.English price group 17No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 19
2、.100!%2m 2/2/arccosSDHObjObjSDH222SDHDsDtDsDtsDD (4) The symbols used in this equation are illustrated in Figure 3. The radius of curvature of the surface used for the calibration shall be within r 10 % of that of the test object. Key 1 Marked line for index shift 2 Index point after contouring 3 In
3、dex point before contouring Figure 2 Determination of index shift for longitudinally curved probes 10DIN EN ISO 16811:2014-06EN ISO 16811:2014 (E)Figure 3 Determination of beam angle . for a longitudinally contoured probe 4.3.2 Reference Block Technique This is similar to that referenced in 4.2.2, e
4、xcept that the test block shall have a radius of curvature within 10% of that of the test object. 4.4 Probes curved transversely 4.4.1 Mechanical determination Before contouring the probe face the probe index and beam angle shall be measured as described in 4.2. After contouring, either i) a line re
5、presenting the incident beam, originating from the probe index, shall be marked on the side of the probe. The new position of the probe index shall be measured on the side of the probe as shown in Figure 4; ii) the shift in probe index position () shall be calculated using equation 5: )( tan dDgx (5
6、) The symbols in this equation are illustrated in Figure 4. )or acrylic glass wedges (Fd=2730 m/s) and non-alloy steel test objects (Ft=3255 m/s) the shift in the probe index position (x), for the three most commonly used beam angles, shall be read from Figure 5 in relation to the depth of contourin
7、g (g). The beam angle should not change during contouring. However, if it is not known, or there is any variation in the depth of contouring along the length of the probe, it shall be measured on a suitably contoured reference block using a side drilled hole satisfying the conditions given in $nnex
8、B. The beam angle shall be determined by: 11DIN EN ISO 16811:2014-06EN ISO 16811:2014 (E)iii) drawing a straight line between the hole and the probe index on a scale drawing; or iv) calculation using, for example, equation (6) for the setup illustrated in Figure 6. tqxAarctanD Key 1 Marked line for
9、index shift 2 Index point after contouring 3 Index point before contouring Figure 4 Determination of index shift for transversely curved probes 4.4.2 Reference block technique This technique is similar to that referenced in 4.2.2 except that the test block shall be curved transversely in relation to
10、 the probe, and shall have a radius of curvature not exceeding 10 % greater, or 30 % lower, than that of the test object. 12DIN EN ISO 16811:2014-06EN ISO 16811:2014 (E)Figure 5 Probe index shift, , for delay paths in acrylic glass Figure 6 Determination of beam angle using a side-drilled hole 4.5 P
11、robes curved in two directions Unless the need for multiaxial curving of the probe face can be avoided, e. g. by use of smaller probes, the procedures specified in 4.2, 4.3 and 4.4 shall be followed as appropriate. 13DIN EN ISO 16811:2014-06EN ISO 16811:2014 (E)4.6 Probes for use on materials other
12、than non-alloy steel If the sound velocity in the material under test is markedly different from that in non-alloy steel, the position of the probe index and the beam angle will be significantly changed. The use of the radii on Calibration Block No. 1 or Calibration Block No. 2 may lead to confusing
13、 results. If the sound velocity is known, the beam angle can be calculated as follows: rrttsinarcsin DDcc(7) where Dr is the beam angle in a non-alloy steel reference block; Dtis the beam angle in the test object; Ftis the transverse wave velocity in the test object; Fris the transverse wave velocit
14、y in the non-alloy steel reference block (3255 m/s r 15 m/s). If the sound velocity is not known, the beam angle can be determined using an echo from a side-drilled hole in a sample of the material, as illustrated in Figure 6, or as described in 4.3.1 or in 4.4.1, as appropriate. 5 Time base setting
15、 5.1 General For all tests using the pulse echo technique, the timebase of the ultrasonic instrument shall be set to indicate, on the screen, the sound propagation time, or, more usually, some parameters directly related to it. Such parameters may be the sound path length of a reflector, its depth b
16、elow the test surface, its projection distance, or its reduced La, projection distance, see Figure 7. Unless otherwise noted, the procedures described below refer to setting the timebase in terms of the sound path length (an echo travels this path twice). Timebase setting shall be carried out with t
17、wo reference echoes having a known time or distance interval between them. Depending on the intended calibration, the respective sound paths, depths, projection distances, or reduced projection distances shall be known. This technique ensures that correction is automatically made for the sound propa
18、gation time through the delay block (e. g. probe wedge). Only in the case of equipment employing an electronically calibrated timebase is one echo sufficient, provided the sound velocity of the reference block is known. The distance between the reference echoes shall be as large as practicable withi
19、n the timebase range. The left-hand rising edge of each echo shall be set, using the timebase shift and expansion controls, to correspond to a predetermined position along the horizontal screen graticule. Where appropriate calibration shall comprise a check signal, which shall not coincide with eith
20、er one of the setting signals, but shall appear at the calculated screen position. 5.2 Reference blocks and reference reflectors For the examination of ferritic steels the use of Calibration block No. 1 or Calibration block No. 2 as specified in ,62 and ,62, respectively, is recommended. If a refere
21、nce block or the test object itself is used for calibration, faces opposite to the test surface or appropriate reflectors at different known sound path lengths may be used as applicable. 14DIN EN ISO 16811:2014-06EN ISO 16811:2014 (E)Reference blocks shall either have a sound velocity within 5% of t
22、hat of the test object, or correction for the velocity difference shall be made. 5.3 Straight beam probes 5.3.1 Single reflector technique This requires a reference block having a thickness not greater than the timebase range to be set. Suitable back wall echoes may be obtained from the 25 mm or 100
23、 mm thickness of Calibration Block No. 1, or the 12,5 mm thickness of Calibration Block No. 2. Alternative reference blocks, having parallel or concentric surfaces, known thickness, and the same sound velocity as the test object, may also be used. 5.3.2 Multiple reflector technique This requires a r
24、eference block (or separate blocks) having two reflectors (e. g. side-drilled holes) at different known sound path lengths. The probe shall be repeatedly repositioned to maximie the echo from each reflector; the position of the echo of the nearest reflector shall be adjusted using the shift (or zero
25、) control and that of the echo of the other reflector using the expansion (or distance) control until an accurate timebase setting is achieved. 5.4 Angle beam probes 5.4.1 Radius technique Range setting can be performed using the radii reflectors of Calibration Block No. 1 or Calibration Block No. 2
26、, as described in ISO 2400 or ISO 7963 respectively. 5.4.2 Straight beam probe technique For transverse wave probes the range setting can be carried out using a longitudinal straight beam probe on the 91 mm thickness of Calibration Block No. 1 (described in ISO 2400), corresponding to a sound path l
27、ength of 50 mm for transverse waves in steel. To complete the range setting it is necessary to obtain an echo, with the probe to be used for examination, from a suitable reflector at a known sound path distance, and using the zero shift control only, to position this echo at the correct location alo
28、ng the timebase. 5.4.3 Reference block technique This is similar in principle to that described in 5.3.2 for straight beam probes. However to achieve adequate accuracy it is necessary to mark the beam index points on the surface of the block at which each echo is first maximied, and then mechanicall
29、y measure the distance between these marks and the corresponding reflectors. For all subsequent timebase adjustments, the probe shall be repositioned on these marks. 5.4.4 Contoured probes Range setting shall first be performed using a probe with a flat face, as described above. The contoured probe
30、shall then be positioned on a suitable contoured reference block having at least one reflector at a known sound path length. The position of the echo from this reflector is adjusted to the correct position along the timebase using only the shift control. 15DIN EN ISO 16811:2014-06EN ISO 16811:2014 (
31、E)5.5 Alternative range settings for angle beam probes 5.5.1 Flat surfaces Instead of setting in terms of sound path length, the timebase may be set to indicate directly the depth of a reflector below the test surface, or its distance in front of the probe, see Figure 7. Therefore, having selected t
32、he timebase in terms of depth or projection distance, the echoes from the reference block, at known sound path lengths, are set along the timebase at the positions corresponding to the equivalent depths, or projection distances, which may be determined as follows: For a flat plate they may be determ
33、ined for a given beam angle, either from a scale drawing, or from the following equations: depth (t): tcos = Dst (8) projection distance (a): tsin Dsa (9) shortened projection distance (a): -) sin ( tDsa (10) 5.5.2 Curved surfaces Whilst the same principles of range setting described in 5.5.1 still
34、apply, the timebase is not linear with respect to depth or projection distance. A non-linear graticule scale may be constructed by taking measurements at a number of positions on a scale drawing of the sound path, or by calculation using suitable equations. The sound path distance to the opposite su
35、rface of a concentrically curved object may be determined using the equations given in $nnex C. Alternatively, the graticule intervals may be determined on the basis of the maximied echoes from a series of reflectors in a curved reference block, the intermediate values being obtained by interpolatio
36、n. See Figure 8. 16DIN EN ISO 16811:2014-06EN ISO 16811:2014 (E)Key 1 Reflector 2 Index point Figure 7 Definitions for setting of the timebase in terms of e. g. reduced projection distance Figure 8 Example of screen graticule for location of reflectors with a time base set in terms of reduced projec
37、tion distance and depth (Here: = 51, VPD= 100 mm) tD17DIN EN ISO 16811:2014-06EN ISO 16811:2014 (E)6 Sensitivity setting and echo height evaluation 6.1 General After the timebase has been calibrated, the sensitivity (or gain adjustment) of the ultrasonic equipment shall be set using one of the follo
38、wing techniques: 1) Single Reflector technique A single reference reflector e.g. a back wall, or a notch, may be used when evaluating echoes occurring within the same range of sound path distance. 2) Distance Amplitude Curve (DAC)-technique This technique uses the echo heights from a series of ident
39、ical reflectors (e.g. side-drilled holes or flat-bottom holes) at different sound path lengths in suitable reference blocks (see 6.3). 3) Distance Gain Size (DGS)-technique This technique uses a series of theoretically derived curves relating the sound path length, the equipment gain, and the size o
40、f a disk-shaped reflector perpendicular to the beam axis (see 6.4). Techniques 2 and 3 attempt to compensate for the change in the echo height from a reflector with increasing sound path distance. However, for all three techniques, a transfer correction shall be applied, where necessary, to compensa
41、te for any coupling losses and differences in material attenuation (see 6.5). Using ideal reflectors of simple shape, e. g. side-drilled holes or flat bottom holes, for sizing of natural discontinuities will not give the true size but only an equivalent value. The true size of the real discontinuity
42、 may be much larger than this equivalent value. 6.2 Angle of impingement When using angle probes on curved test objects in conjunction with indirect scanning (i. e. after the skip position), the incident angle at the back wall, i. e. the angle of impingement, should be considered. In the case of cyl
43、indrical components scanned from the outer surface, the incident angle at the inner surface may be very much larger than the beam angle. Conversely, when scanning from the inner surface the incident angle at the outer surface may be very much smaller than the beam angle (see $nnex C). For transverse
44、 wave probes, the beam angle shall be chosen to avoid impingement angles outside the range 35 to 70, because in that case severe loss in sound energy will occur due to mode conversion. Moreover, additional echoes from other wave modes may disturb echo evaluation. A technique for determining the impi
45、ngement angle at the inner and outer surfaces of a cylinder is described in $nnex C together with methods of calculating the sound path distance to the opposite surface. 6.3 Distance Amplitude Curve (DAC) technique 6.3.1 Reference blocks A DAC reference block is required having a series of reflector
46、s at different sound path distances over the timebase range to be used for the test. Details of the spacing and minimum size of block and reflectors are given in $nnex B. The specifications given in $nnex B apply for category 1 objects, and, where appropriate, for category 2 to category 5 test objec
47、ts. It should be noted that there are minimum sound path lengths below which signals cannot be satisfactorily evaluated due to e. g. dead zone effects or near field interference. 18DIN EN ISO 16811:2014-06EN ISO 16811:2014 (E)N1) National footnote: In the original ISO document, the list erroneously
48、started with item 2). This has been corrected in the German version and correspondingly in the English version. N1)1) a general purpose block of uniform low attenuation and specified surface finish, and having a thickness within 10% of the test object; or 2) a block of the same acoustic properties,
49、surface finish, shape and curvature as the test object. In the case of type 1), correction for any differences in attenuation, curvature and coupling losses may be necessary before the Distance Amplitude Curve can be directly applied. 6.3.2 Preparation of a Distance Amplitude Curve The distance amplitude curve shall be either shown directly on the screen of the i
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