GB/T Translated English of Chinese Standard: GB//T NATIONAL STANDARD OF THE

Transcription

1 Translated English of Chinese Standard: GB//T GB NATIONAL STANDARD OF THE PEOPLE S REPUBLIC OF CHINA ICS J 33 GB/T Replacing GB/T Non-destructive Testing of Welds - Ultrasonic Testing - Techniques, Testing Levels, and Assessment 焊缝无损检测超声检测技术 检测等级和评定 (ISO 17640:2010, MOD) Issued on: September 18, 2013 Implemented on: June 01, 2014 Issued by: General Administration of Quality Supervision, Inspection and Quarantine; Standardization Administration of the People's Republic of China. Page 1 of 55

2 Table of Contents Foreword Scope Normative References Terms, Definitions and Symbols Principle Information Required Prior to Testing Requirements for Personnel and Equipment Testing Volume Scanning Zone Parent Metal Testing Time Base and Sensitivity Setting Testing Levels Testing Techniques Testing Report Annex A (Normative) Testing Levels for Various Types of Welded Joints Annex B (Normative) Tandem Testing Annex C (Informative) Technical Parameters of Equipment Annex D (Normative) Calculation of Actual Refraction Angle of Curved Surface Parts Annex E (Normative) Setting of Time Base and Sensitivity Annex F (Normative) Transmission Correction Page 2 of 55

3 Foreword This standard is drafted according to the rules specified in GB/T This standard replaces GB/T "Method for Manual Ultrasonic Testing and Classification of Testing Results for Ferritic Steel Welds". Compared with GB/T , the main technical changes of this standard are as follows: "Scope" is modified (see Chapter 1 of this edition; Chapter 1 of 1989 edition) "Normative References" is modified (see Chapter 2 of this edition; Chapter 2 of 1989 edition); "Terms, Definitions and Symbols" is modified (see Chapter 3 of this edition; Chapter 3 of 1989 edition); "Principle" is added (see Chapter 4 of this edition); The "items to be specified" in the contractual agreement, "specific information required before testing" and "written testing procedure" are added (see Chapter 5 of this edition); "Requirements for Personnel and Equipment" is modified (see Chapter 6 of this edition; Chapter 4, Chapter 5 and Chapter 6 of 1989 edition); "Testing Volume" is modified (see Chapter 7 of this edition; 8.1 in 1989 edition); "Scanning Zone" is modified (see Chapter 8 of this edition; 8.1 in 1989 edition); "Parent Metal Testing" is modified (see Chapter 9 of this edition; 8.5 in 1989 edition); Time base scanning and sensitivity adjustment or checking are modified; requirements for checking temperature, corrective measures for deviation and testing techniques for adjusting or checking datum line reference level are added; setting methods for assessment line are deleted and transmission correction methods are modified (see Chapter 10 of this edition; Chapter 9 of 1989 edition); "Testing Level" is modified (see Chapter 11 of this edition; Chapter 7 of 1989 edition); "Testing Techniques" is modified (see Chapter 12 of this edition; Chapters 10 and 11 of 1989 edition); "Defects Assessment and Rating" is deleted (see Chapter 12 and Chapter 13 of Page 3 of 55

4 1989 edition); "Testing Report" is modified (see Chapter 13 of this edition; Chapter 14 of 1989 edition); Annex A ~ Annex F are added while Annex A ~ Annex F of 1989 edition are deleted. This standard is redrafted and modified in relation to ISO 17640:2010 "Non-destructive Testing of Welds - Ultrasonic Testing - Techniques, Testing Levels, and Assessment" (English version). The main technical differences and their reasons between this standard and ISO 17640:2010 are as follows: As for the chapter of "Normative References", some technical differences adjustments are made in order to adapt the technical conditions in China, the adjustment conditions are reflected in Chapter 2 "Normative References" and the specific adjustments are as follows: GB/T 29712, is modified in relation to and in place of international standard ISO (see Chapter 4, and 10.3); GB/T 29711, is modified in relation to and in place of international standard ISO (see Chapter 4, and ); ISO is deleted and the information related to this standard is added to Chapter 11 (see Chapter 11); EN is deleted and the items by reference to EN are prepared into this standard (see 6.3.5); EN is deleted and the information related to this standard is distributed to Annex D (see 6.3.2), Annex E (see 10.1) and Annex F (see 10.4); EN is deleted and the information related to this standard is added to Annex B (see 5.1); GB/T is added (see Annex E.2, Annex E.3 and Annex E.4); GB/T is added (see Annex E.2, Annex E.3 and Annex E.4); GB/T 5616 is added (see 6.2.1); GB/T is added (see 6.2.1); JB/T 9214 and JB/T are in place of EN (all the parts) (see 6.2); Page 4 of 55

5 Schematic diagram for probe contact surface width is added (see Figure 1 in 6.3.4). This standard has the following editorial changes: GB/T is equivalent to and in place of international standard ISO 5817 (see Chapter 11); GB/T 9445, is equivalent to international standard and in place of international standard ISO 9712 and EN 473 (see 6.1); GB/T , is equivalent to and in place of international standard EN (see 3.1). This standard was proposed by and shall be under the jurisdiction of National Technical Committee on Welding of Standardization Administration of China (SAC/TC 55). Drafting organizations of this standard: Shanghai Research Institute of Materials, China Special Equipment Inspection and Research Institute, Shandong Jining Mould Tool Factory, Zhejiang Provincial Special Equipment Inspection and Research Institute, CSR Qishuyan Institute Co., Ltd. Chief drafting staffs of this standard: Zheng Hui, Zhuang Zhiqiang, Jin Yufei, Ding Jie, Jiang Wei, Wei Zhongrui, Huang Wenda, Wan Shengyun, Wang Sen, Zhang Wenjie, Xi Lifeng, Ma Jun. The previous edition replaced by this standard is as follows: GB/T Page 5 of 55

6 Non-destructive Testing of Welds - Ultrasonic Testing - Techniques, Testing Levels, and Assessment 1 Scope This standard specifies the techniques for the manual ultrasonic testing of fusion-welded joints in metallic materials with thickness greater than or equal to 8 mm which exhibit low ultrasonic attenuation (especially that due to scatter) at object temperatures from 0 to 60. It is primarily intended for use on full penetration welds where both the welded and parent material are ferritic. Material-dependent ultrasonic values are specified in this standard, they are based on steels having an ultrasonic sound velocity of (5920 ± 50) m/s for longitudinal waves and (3255 ± 30) m/s for transverse waves. This standard specifies four testing levels, each corresponding to a different probability of detection of imperfections. Guidance on the selection of testing levels A, B and C is given in Annex A. This standard specifies that the requirements of testing level D, which is intended for special applications, be in accordance with general requirements. Testing level D can only be used when defined by specification. This includes tests of metals other than ferritic steel, tests on partial penetration welds, tests with automated equipment, and tests at object temperatures outside the range 0 to 60. This standard can be used for the assessment of indications, for acceptance purposes, by either of the following techniques: a) assessment based primarily on length and echo amplitude; b) assessment based on characterization and sizing of the indication by probe movement techniques. The techniques used shall be specified. 2 Normative References The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. Page 6 of 55

7 GB/T 5616 Non-destructive Testing - Guidelines for Application GB/T 9445 Non-destructive Testing - Qualification and Certification of Personnel (GB/T , ISO 9712:2005, IDT) GB/T Terminology for Nondestructive Testing - Ultrasonic (GB/T , ISO 5577:2000, IDT) GB/T Arc-welded Joints in Steel - Guidance on Quality Levels for Imperfections (GB/T , ISO 5817:1992, IDT) GB/T Non-destructive Testing - Ultrasonic Testing - Calibration Block No.1 (GB/T , ISO 2400: 1972, IDT) GB/T Non-destructive Testing - Ultrasonic Testing - Specification for Calibration Block No.2 (GB/T , ISO 7963:2006, IDT) GB/T Non-destructive Testing - Blocks for Ultrasonic Testing GB/T Non-destructive Testing of Welds - Ultrasonic Testing - Characterization of Indications in Welds (ISO 23279:2010, IDT) GB/T Non-destructive Testing of Welds - Ultrasonic Testing - Acceptance Levels (ISO 11666:2010, MOD) JB/T 9214 Non-destructive Testing - Practice for Evaluating Performance Characteristics of A Scope Ultrasonic Pulse - Echo Testing Systems JB/T Commonly used Specification for A-mode Ultrasonic Flaw Detector Using Pulse Echo Technique 3 Terms, Definitions and Symbols 3.1 For the purposes of this standard, the terms and definitions given in GB/T apply. 3.2 For symbols, their definitions, and units, see Table 1. Indications shall be considered to be either longitudinal or transverse, depending on the direction of their dimension with respect to the weld axis, x, in accordance with Figure 3. Table 1 Symbols, their Definitions, and Units Symbol Definition Unit D DSR diameter of the disk-shaped reflector mm h extension of the indication in depth direction mm Page 7 of 55

8 5.2 Specific information required before testing Before any testing of a welded joint can begin, the operator shall have access to the following essential information: a) written testing procedure, if required (see 5.3); b) type(s) of parent material and product form (i.e. cast, forged, rolled); c) manufacturing or operation stage at which testing is to be made, including heat treatment, if any; d) time and extent of any post-weld heat treatment; e) joint preparation and dimensions; f) requirements for surface conditions; g) welding procedure or relevant information on the welding process; h) reporting requirements; i) acceptance levels; j) extent of testing, including requirements for transverse indications, if relevant; k) testing level; l) personnel qualification level; m) procedures for corrective actions when unacceptable indications are revealed. 5.3 Written testing procedure The definitions and requirements in this standard normally satisfy the need for preparing a written testing procedure. Where this is not the case, or where the techniques described in this standard are not applicable to the weld joint to be examined, additional written testing procedures shall be used, if required by specification. 6 Requirements for Personnel and Equipment 6.1 Personnel qualifications The testing personnel under this standard shall be subjected to qualification approval Page 9 of 55

9 methods in JB/T The ultrasonic detector should meet the following requirements unless otherwise specified: a) Temperature stability: ambient temperature varies ±5 ; signal varies ±2% of full screen height (FSH) or less; position varies ±1% of full screen width or less; b) Indication stability: frequency increases by about 1 Hz; signal varies ±2% of full screen height (FSH) or less; position varies ±1% of full screen width or less; c) Horizontal linearity deviation is less than or equal to ±2% of full screen width; d) For vertical linearity, the deviation of the measured value from theoretical value is less than or equal to ±3%. The organizations responsible for issuing instrument performance testing report shall be qualified and the validity period of the report should not be longer than 12 months System performance testing At least prior to each testing, the ultrasonic examination systems shall be tested for working performance according to the recommended methods in JB/T The system performance should meet the following requirements unless otherwise specified: a) As for the incidence point of the angle probe for locating imperfection, the deviation of the measured value from the nominal value is less than or equal to ±1 mm; b) As for the angle of refraction of the angle probe for locating imperfection, the deviation of the measured value from the nominal value is less than or equal to ±2 ; c) Sensitivity allowance, resolution and dead zone depends on the practical application. The system performance shall be detailed in the written testing procedure with regards to testing items, opportunity, period and performance requirements. 6.3 Probe parameters Testing frequency The frequency shall be within the range 2 MHz to 5 MHz, and shall be selected to comply with the specified acceptance levels. Page 11 of 55

10 When the indication is assessed according to GB/T 29712, a testing frequency as low as possible shall be chosen within the above range for the initial testing; when the indication is assessed according to GB/T 29711, a higher testing frequency may be chosen if necessary to improve the probe resolution. Frequencies of approximately 1 MHz may be used where the attenuation coefficient of the tested object shows above average attenuation coefficient of the materials Angles of incidence When testing is carried out with transverse waves and techniques that require the ultrasonic beam to be reflected from an opposite surface, care shall be taken to ensure that the angle between the beam and the normal to the opposite reflecting surface is between 35 and 70. Where more than one probe angle is used, at least one of the angle probes used shall conform with this requirement. The beam of one probe shall be as vertical as possible to the weld fuse surface. The difference of angle of refraction for more than one probe shall be 10 or greater. The actual angle of refraction and angle of reflection for the workpieces may be determined by weld section diagram when the testing surface is curved, as shown in Annex D. Where angles of incidence cannot be determined as specified by this standard, the testing report shall contain scanning zone of beam, and the extent of any incomplete coverage and the explanation for those conditions Element size The element size shall be chosen according to the ultrasonic path to be used and the frequency. The smaller the element, the smaller the length and width of the near field, and the larger the beam spread in the far field at a given frequency. Small probes having 6mm to 12mm diameter elements (or rectangular elements of equivalent area) are therefore most useful when working at short beam path ranges. For longer ranges, i.e. greater than 100 mm for single normal beam probes and greater than 200 mm for angle beam probes, an element size of 12 mm to 24 mm is more suitable Adaptation of probes to curved scanning surfaces The gap, g, between testing surface and probe shoe bottom shall not be greater than 0.5mm. For cylindrical or spherical surfaces, this requirement can be checked with the equation below: Page 12 of 55

11 foreign matters. Waviness of the scanning zone shall not result in a gap between the probe and workpieces contact surfaces greater than 0.5 mm. Dressing surface of scanning zone is required if the gap exceeds the limit. If local deformation in weld surface results in a gap between probe and weld up to 1mm, the probes of other angles may be employed from the affected side for supplemental scanning. The local deformation is permissible if the scanning is necessary to compensate for the testing volume not to be scanned. Scanning zone and surfaces from which the sound beam is reflected shall allow undisturbed coupling and reflector. 9. Parent Metal Testing The parent metal, in the scanning zone (see Figure 2), shall be examined with longitudinal wave prior to or after welding, unless it can be demonstrated (e.g. previous testing during the fabrication process) that the transverse wave testing is not influenced by the presence of the imperfections or high attenuation. Where imperfections are found on the parent metal, their influence on the transverse wave testing effect shall be assessed. If necessary, the weld ultrasonic testing techniques are adjusted correspondingly. When a testing volume fully by sound beam is seriously affected, other inspection techniques (e.g. radiography) shall be considered. 10. Time Base and Sensitivity Setting 10.1 General Setting of time base and sensitivity shall be carried out prior to each testing in accordance with this standard and Annex E, taking the influence of temperature into account. The temperature difference during time base and sensitivity setting and during the weld testing shall be within ±15. Checks to confirm these settings shall be performed at least every 4h and on completion of the testing. Checks shall also be carried out whenever a system parameter is changed or changes in the equivalent settings are suspected. If deviations are found during these checks, the corrections given in Table 2 shall be carried out. Table 2 Sensitivity and Time Base Corrections Sensitivity 1 Deviations 4 db Setting shall be corrected before the testing is continued. 2 Reduction of the Setting shall be corrected and all testing carried out with the equipment over Page 15 of 55

12 1.5~2.5 D DSR =2.5 mm D DSR =2.5 mm D DSR =3.0 mm D DSR =3.0 mm 3.0~5.0 D DSR =2.0 mm D DSR =2.0 mm D DSR =2.0 mm D DSR =2.0 mm D DSR =3.0 mm D DSR =3.0 mm D DSR is the diameter of the disk-shaped reflector Assessment levels All indications equal to or exceeding the assessment level shall be evaluated. The assessment levels for techniques 1 to 4 are given in GB/T 29712, Table A Transmission correction When reference blocks are used for establishing reference levels, the transfer loss difference of sound energy shall be measured, between test object and block, at a representative number of locations. Suitable techniques are described in Annex F. If the differences are less than or equal to 2 db, correction is not required. If the differences are greater than 2 db but smaller than 12 db, they shall be compensated for. If transfer losses exceed 12 db, the reason shall be considered and further preparation of the scanning zone shall be carried out, if applicable. When there are no apparent reasons for large transfer loss difference on the test object, the transfer loss at various locations on the test object, shall be measured and corrective actions shall be taken Signal to noise ratio During testing of the weld, the noise level, excluding spurious surface indications, shall remain at least 12 db below the assessment level. This requirement may be relaxed subject to the specification. 11. Testing Levels Quality requirements for welded joints are mainly associated with the material, welding process and service conditions. To accommodate all of these requirements, this standard specifies four testing levels (A, B, C, and D). From testing level A to testing level C, increase testing coverage by increasing scanning number and scanning zone and improve imperfection detection rate. Testing level D may be agreed for special application using a written procedure which shall take into account the general requirements of this standard. In general, the testing levels are related to weld quality levels (e.g. GB/T 19418). The appropriate testing level may be specified by standards for testing of welds, product standards or other Page 17 of 55

13 1) material and product form; 2) dimensions; 3) location of weld/welded joint examined; 4) sketch showing geometrical configuration (if necessary); 5) welding procedure, specification and heat treatment; 6) state of manufacture; 7) surface conditions; 8) temperature of the object. b) contract requirements, e.g. specifications, guidelines, special agreements, etc.; c) place and date of testing; d) identification of test organizations and identification and certification of operator; e) maker and type of ultrasonic instrument with identification number, if required; f) maker, type, nominal frequency, size of element and actual angle of incidence of probes used with identification number, if required; g) identification of reference blocks used with a sketch, if necessary; h) couplant medium; i) testing level(s) and reference to written procedure when used; j) extent of testing; k) location of the scanning areas; l) reference points and details of coordinate system used as specified in 12.4; m) identification of probe positions, as specified in Annex A or by use of a sketch; n) time base range; o) method and values used for sensitivity setting (gain setting for reference levels and values used for transmission corrections); p) reference levels; Page 21 of 55

14 Key, 1 component 1; 2 component 2; A, B, C, D, E, F, G, W, X, Y, Z probe positions; a, b, c, d, e, f, g Scanning zone width; t thickness Figure A.2 Structural T-joints Table A.2 Structural T-joints (See Figure A.2 for Typical Structure) Testin g level A Longitudinal indications Transverse indications Thickness Required number Required number of the parent Probe Probe Scanning Probe Scanning Total Probe Probe Scanning Total material angle positions zone position zone number angle positions zone number Notes mm s width s width of scans s width of scans L-scans N-scans T-scans 8 t<15 1 A or B 1.25ρ C c 1 a 15 t<40 1 A or B 1.25ρ C c c 2 a 8 t<15 1 A or B 1.25ρ C c 2 1 F and G c 2 b (F and 15 t<40 1 A and B 1.25ρ C c c 3 1 G) or (X and Y) or (W c f + g 2 b and Z) B (F and 40 t A and B 0.75ρ C c c 5 1 G) or (X and Y) or (W c f + g 2 b and Z) 8 t<15 1 A and B 1.25ρ C c c 3 2 F and G (F and c f + g 4 b 15 t<40 21 (A and B) and (D and E) 1.25p d + e C c c 7 1 G) and (X and Y) or (W c f + g 4 b and Z) (F and C 40 t (A and B) and (D and E) 0.75ρ d + e C c c 7 2 G) and (X and Y) or (W c f + g 8 b and Z) > (A and B) and (D and E) O.75ρ d + e C c c 9 2 (F and G) and (X and Y) c f + g 8 b Page 25 of 55

15 two parallel end faces: y=2tanα(d-t m ) If a=45 : y=2(d-t m ) Scanning may be carried out by either method below: Two probes moves along the workpiece surface at a fixed probe spacing (y). This method can only test a testing volume of a certain depth. The probe spacing shall be adjusted to cover the testing volume under the whole depth section. Two probes move together in such a way to remain their acoustic axes are at grade intersection and at a constant distance sum (the acoustic axis shall be vertical to weld axis), therefore scanning the whole thickness in one continuous motion. B.2 Time base adjustment Basically all the relevant echo waves indicate the same ultrasonic path distance and comply with V ultrasonic path. It is recommended that the echo wave at V ultrasonic path is set at a fixed position, such as 8 th grid of time base. B.3 Sensitivity setting Use the following reflectors for sensitivity setting: Parallel planes: back wall echo forms V path reflected wave; Disk-shaped reflector: vertical to scanning surface and at the intersection of acoustic axes; Side drilled holes: at the intersection of acoustic axes and at the testing volume edge. B.4 Testing volume calculation Equal testing volume is divided to ensure the sensitivity is not reduced. The calculation of the height of the testing volume: the sensitivity at the edge of the testing volume is up to 6dB less than that at the intersection of acoustic axes, as shown in Figure B.2. Page 35 of 55

16 Annex C (Informative) Technical Parameters of Equipment Common technical parameters for ultrasonic detector and probe are given in this Annex and provided by the manufacturer. If agreed by the manufacturer and the customer, contents concerned of technical parameters in this appendix can be deleted or added. C.1 Ultrasonic instrument C.1.1 General characteristic parameters cover: a) dimensions; b) masses; c) power supply types adopted; d) models of probe plug; e) battery working time (in case of maximum power dissipation of new battery); f) range of temperature and voltage (power supply and/or battery) (operating within the range of given technical index); preheating duration required in case of preheating; g) display mode of low voltage (in case the ultrasonic instrument fails to work normally); h) variation percentage of standard constant signal amplitude and horizontal baseline position within the range of battery voltage during regular discharging and charging of battery; i) pulse repetition frequency (PRF) (switch position and/or variable range); j) Non-detection and/or detection signal that can be output (by way of socket); k) gate signal output provided (i.e.: go/no go and/or proportional output and its response time, linearity, and drive capability and stability of the maximum current of proportional output; threshold delaying and precision of go/no go gate, and holding time of switched output). Page 38 of 55

17 g) minimum input voltage for the height 10% of the screen height within the range of all specified frequencies; h) dynamic range of the ultrasonic instrument within the range of all specified frequencies; i) equivalent input impedance of ultrasonic instrument within the range of specified frequency; j) distance amplitude calibration functions cover: dynamic range, maximum calibration gradient (db/microsecond), calibration mode and influence of DAC control. C.1.5 Besides items mentioned above, the digital ultrasonic instrument also covers: a) digital to analog conversion; b) pixel value in Type A display; c) data output and storage equipment; d) printout; e) calibrated storage equipment; f) display and access facility; g) automatic calibration; h) type and response time of the display. If necessary, such items are also covered as sampling frequency adopted, influence on pulse repetition frequency indication range from sampling frequency and response time, mathematical principle for display data processing and edition of the install software. C.2 Ultrasonic probe Characteristic parameters of the ultrasonic probe cover: a) manufacturer's name; b) probe type; c) probe mass and dimension; d) joint type; e) TR connecting line (sending-receiving), replaceable; Page 40 of 55

18 f) material of the transducer; g) shape and dimension of the transducer; h) material and detention of wedging block; i) material made of wear resistant sheet; j) allowable tolerance for wear resistance; k) crosstalk attenuation; l) pulse waveform (time and frequency); m) center frequency and band width; n) pulse echo sensitivity; o) distance amplitude curve; p) impedance direct capacitance; q) incidence point of probe; r) sound beam angle; s) divergence angle; t) sound beam axis offset; u) angle of deviation; v) focal distance and near field; w) focal point width; x) focal point length; y) appearance. Page 41 of 55

19 path distance from the exploration surface of reference block or tested workpiece to the reflector is known, it may be used to calibrate the time base. The error between reference block and tested workpiece shall be within ±5%, otherwise, it shall be corrected. E.3 Normal probe adjustment technique E.3.1 Simple reflector adjustment The thickness of reference block shall not exceed the setting range of time base. Proper bottom echo wave can be obtained from the 25mm-thick point or the 100mm-thick point of #1 calibration block or from the 12.5mm-thick point of #2 calibration block. Tested workpiece of which the thickness is known can also be selected; the test block shall have flat surface of curved surface identical to that of the workpiece, and sound velocity of both test block and workpiece shall be the same. E.3.2 Multiple reflector adjustment It is required the reference block (or combined block) shall have two reflectors (e.g. side-drilled holes) with different ultrasonic paths. Move the probe position repeatedly and continuously to find the highest echo wave of each reflector, then set echo waves of two adjacent reflectors to accurate position by adjusting the time base scanning control knob so as to calibrate the time base. E.4 Angle probe adjustment technique E.4.1 Adjustment of test block's arc surface Set the time base by way of the arc surface of #1 calibration block or #2 calibration block. E.4.2 Longitudinal wave probe adjustment and switching The time base of transverse wave probe can be set at the 91mm-thick point of #1 calibration block by way of longitudinal wave probe, which is corresponding to the 50mm-transverse wave ultrasonic path in steel. After the setting of time base, the subsequent setting of time base can be performed only by way of zero calibration knob through the probe used in testing and the reflector with known ultrasonic path distance. E.4.3 Reference block adjustment Such adjustment is similar to the adjustment principle for normal probe mentioned in E.3.2. In order to achieve adequate accuracy, the highest echo wave must be found by marking out the sound beam incidence point on test block surface and then Page 48 of 55

20 After the calibration of time base, the sensitivity (gain control) of ultrasonic equipment shall be set in accordance with any technique below: a) Simple reflector technique In case that the ultrasonic path distance of the echo wave evaluated is identical to that of the reference reflector echo wave, the simple reference reflector can just be utilized for reference. b) Distance amplitude curve (DAC) technique DAC curve is such drawn by obtaining series of identical reflector (e.g. side-drilled hole or flat bottom hole) echo waves with different ultrasonic paths. c) DGS technique Such technique is realized by utilizing a series of export curves relevant to ultrasonic path, gain and dimension of flat bottom hole vertical to sound beam axis. E.6.2 Angle influence If the angle probe secondary wave (e.g.: behind the semi-span) is used to test the curved surface parts, the incidence angle variation (e.g. angle influence) induced by bottom surface shall be considered. If the probe scans the cylindrical workpiece from external-circle surface, the sound beam angle will increase due to the reflection of inner surface for it is a kind of curved surface. On the contrary, if the probe scans from inner circle surface, the sound beam angle will diminish due to the reflection of external surface for it is a kind of curved surface. E.6.3 Distance amplitude curve (DAC) technique The reference block used for drawing DAC curve shall be provided with a series of reflectors with series of different ultrasonic path distances, and the depth of reflector on test block shall be greater than the height of tested workpiece. See Table E.1 for specific requirements for space, minimum dimension of test block and reflector. Heights of different echo waves shall be evaluated in the manner below: If the echo wave height reaches the reference line by increasing XdB, it will be recorded as (reference level-x)db. If the echo wave height reaches the reference line by reducing YdB, it will be recorded as (reference level + Y)dB. Page 50 of 55

21 Annex F (Normative) Transmission Correction Unless the acoustic performance of test block adopted in setting of testing sensitivity can represent the tested workpiece, the transmission correction shall be considered in setting the testing sensitivity or evaluating non-continuous echo wave height. The transmission correction V t consists of two parameters: 1) coupling attenuation on the testing surface, irrelevant to ultrasonic path; 2) material attenuation, related to ultrasonic path. Description on two methods: one is called fixed ultrasonic path method, i.e. the compensation dosage consists of coupling loss and material attenuation only at the maximum ultrasonic path point; the other is called comparison method, i.e. the compensation dosage consists of these two parameters. F.1 Fixed ultrasonic path method This method is only applicable for the case that the sound energy attenuation is less than coupling loss or the reflector echo wave approaches the workpiece bottom. In the adoption of normal probe, respectively adjust the primary bottom echo waves of the reference block and the workpiece to the same height of the oscilloscope screen, and write down the corresponding db values (represented with V t, t and V t, r ). In the adoption of angle probe, place two identical probes (one for sending and the other for receiving) in V-shaped manner to obtain corresponding echo waves. If ultrasonic paths of two bottom echo waves are different, the ultrasonic path difference ( V s ) between two echo waves can be obtained from DGS curve, and the transmission correction ( V t ) can be calculated in accordance with the formula below: F.2 Comparison method F.2.1 Normal probe V t =V t, t - V t, r - V s Place the probe on the reference block, respectively adjust the first and the second bottom waves to the same height on the oscilloscope screen and record corresponding gain values (see Figure F.1 for V A1 and V A2 ). Draw line 2 in Figure G.1 in accordance with the relation between gain value and ultrasonic path distance. Then, replace the probe on the workpiece and repeat the above procedures to obtain Page 53 of 55