GB/T 29711-2013Non-destructive testing of welds -- Ultrasonic testing -- Characterization of indications in welds (English PDF)

4.1 Overview

The display is sorted in order by the following criteria.

a) echo amplitude;

b) directional reflection;

c) static echo waveform (A-scan);

d) Dynamic echo waveform.

The above criteria can be implemented through a flow chart (see Appendix A).

When judging and characterizing the display, it is recommended to use the same probe. The flow chart will show the classification system standardization. Pass and distance

Several thresholds (in decibels) compared to the amplitude curve (DAC) or compared to the maximum echo amplitude from different directions in discontinuities

Said).

The thresholds used in the different steps in the flow chart are shown in Table A.1.

The flow chart is divided into 5 steps.

a) Step 1.Very low echo amplitude display, no classification;

b) Step 2.High echo amplitude display, classified as flat;

c) Step 3.The main classification is not fused;

d) Step 4.Mainly classify inclusions;

e) Step 5.Mainly classify cracks.

Note. According to the flow chart, the hybrid display that exists between the inclusions and the unfused contract is classified as a flat type. An example of this type of injury is shown in Figure A.2.

4.2 Echo amplitude criteria (steps 1 and 2)

4.2.1 Low echo amplitude (step 1)

The echo amplitude is lower than the rating specified in ISO 11666 (defined as T1 in Figure A.1). The display is irrelevant and should not be performed.

The levy can be accepted.

For special applications, the T1 value can be reduced if specified in the technical agreement.

4.2.2 High echo amplitude (step 2)

The echo amplitude is not less than the display level of 6dB (defined as T2 in Figure A.1), and the classification is displayed.

4.3 Directional Reflection Guidelines (Step 3)

4.3.1 Determination of applicability based on display length

Step 3 in the flowchart should only be used to display longer than.

a) t, 8mm <= plate thickness t <= 15mm;

b) t/2 or 15mm, whichever is greater, when the thickness is t >15mm.

If there is no display exceeding the above specified length, proceed as in step 4.

4.3.2 Application conditions

Perform the following application conditions.

a) the echoes compared should be from the same reflector;

b) The echo comparison should be made when the displayed echo reaches the highest position Hd,max;

c) When using both straight and oblique probes, select the appropriate probe frequency so that the wavelengths of the shear and longitudinal waves are approximately equal (eg

4MHz longitudinal wave and 2MHz transverse wave);

d) When using two or more oblique probes, the difference between the nominal refraction angles should be greater than or equal to 10°;

e) If the echo passing through the weld is compared to the echo only through the parent metal, the attenuation in the weld should be considered.

4.3.3 Guidelines

For the same display, compare the highest echo amplitude Hd,max with the lowest echo amplitude Hd,min obtained from other directions.

To meet directional reflection, the following conditions should be met.

a) Hd,max>=T3 (reference level -6dB);

b) The difference between the displayed echo amplitudes obtained from 2 different directions |Hd,max-Hd,min|, at least.

1) 9dB, only with a transverse wave oblique probe, or

2) 15dB, with 1 transverse wave oblique probe and 1 longitudinal wave straight probe.

Directional reflection depends on the angle of refraction and the detection conditions (half span, full span).

For an example of different detection directions, see Figure B.1.

For an example of applying this guideline, see Figure B.2.

4.4 Static Echo Waveform Guidelines (Step 4)

In this step, the static echo waveform of the displayed static echo waveform (for example. A-scan) and the reference reflector (3 mm diameter transverse hole)

Compare.

If the static echo waveform is single and smooth, the display is classified as non-planar.

If the static echo waveform is neither single nor smooth, proceed as in step 5.

It should be tested in at least 2 directions to comply with this Code.

4.5 Lateral Dynamic Echo Waveform Guidelines (Step 5)

The displayed horizontal dynamic echo waveform is the echo obtained when the probe moves in the direction perpendicular to the display length according to ISO 17640.

Envelope. In the analysis, not only the envelope but also the echo changes in the envelope should be considered.

The classification shown depends on the waveform obtained.

a) Waveform 1.a single non-planar display;

b) waveform 2.a non-planar display that does not belong to waveform 1;

c) Waveform 3 and Waveform 4.Flat display, if the highest reflection in 2 directions is observed, or if only 1 reflection is observed

To, use additional testing (see 4.6);

d) Waveform 5.Dense non-planar display.

The waveform classification rules are given in Appendix C.

It should be tested in at least 2 directions to comply with this Code.

4.6 Additional testing

Perform additional tests if there is suspicion, such as.

a) increase the direction of reflection or the probe;

b) Analyze the echo envelope obtained when the probe is moved parallel to the display length. [See Figure C.1c), Figure C.2c),

Figure C.3c), Figure C.4c) and Figure C.5c)];

c) Results obtained using other non-destructive testing methods (eg radiographic testing).

The items listed above are not restricted.

Appendix A (normative appendix)

Internal display classification flow chart in weld

The flow chart is shown in Figure A.1.

Description.

Hd --- shows the amplitude of the echo;

Hd,max --- the highest echo amplitude;

Hd,min---lowest echo amplitude;

L --- length;

Lspec --- prescribed length;

T1, T2, T3, T4--- see Table A.1.

Figure A.1 Flowchart

Table A.1 Thresholds used in flowcharts

Threshold T1 T2 T3 T4

Threshold rating level reference level 6dB reference level -6dB 9dBa or 15dBb a Transverse wave.

b between the transverse wave and the longitudinal wave reflection.

Step 1 (T1, for example rating). When all echo amplitudes <= T1 are displayed, they are not classified.

Step 2 (T2, for example, reference level 6 dB). When the display reaches at least 2 times the reference echo, it is classified as a flat type.

Step 3 (T3, for example, reference level -6dB). When the displayed echo amplitude is at least half of the reference echo, and the reflected echo amplitude difference

Greater than or equal to T4, classified as a flat display.

--- When both probes are used for shear wave detection, T4 = 9dB;

---When one probe is used for transverse wave detection and the other probe is for longitudinal wave detection, T4=15dB;

The angle of the ultrasound beam incident on the display should be at least 10° apart.

The comparison should be made in the same area shown.

Steps 4 and 5.Compliance with this Code should be performed in at least 2 directions.

Step 5.If the dynamic echo waveform does not match the graph 3, it is classified as non-planar.

See Appendix C for definitions of echo waveforms.

The mixed type display of inclusions and unmelted contracts is classified into a flat type in the flow chart, as shown in Figure A.2.

Figure A.2 Mixed display example for inclusions and unmelted contracts

Appendix B (informative appendix)

Directional reflection

Description.

A, B, C--- probe position;

L --- longitudinal wave;

T --- transverse wave;

1 --- Welded parts of the weld.

Figure B.1 Example of detection direction

Description.

1 --- position 1;

2 --- position 2;

3 --- reference level;

4 --- reference level -9dB;

d --- sound path;

H---Echo amplitude.

Figure B.2 Application example of directional reflection criteria

Appendix C (informative appendix)

Basic dynamic waveform of the reflector

C.1 waveform 1

Similar to the waveform of a point reflector, see Figure C.1.When the probe is in any position, the A type is shown as a single sharp echo. Probe

When moving, the A sweep echo smoothly rises to the highest wave and then smoothly drops to the noise level.

a) Probe position and echo amplitude variation for A-scan b) Typical example in the thickness direction c) Typical example in the length direction

Description.

1 ---A type scanning;

2 --- peak change;

3 --- reflector;

4 --- weld;

d --- the baseline range at the level;

H---the amplitude of the echo;

x --- Probe position.

Figure C.1 Waveform of the ultrasonic response 1

C.2 Waveform 2

A smooth reflector waveform with a certain extension length, see Figure C.2.When the probe is in any position, the A type is shown as a single sharp echo.

When the ultrasonic beam moves along the reflector, the A sweep wave smoothly rises to a certain height and keeps the peak value within 4 dB. Sound beam separation

When the reflector is turned on, it is smoothly reduced to the noise level.

a) Probe position and echo amplitude variation for A-scan b) Typical example in the thickness direction c) Typical example in the length direction

Description.

1 ---A type scanning;

2 --- peak change;

3 --- reflector;

d --- the baseline range at the level;

H---the amplitude of the echo;

x --- Probe position.

Figure C.2 Waveform of the ultrasonic response 2

C.3 Waveform 3

There are two kinds of rough reflector waveforms with a certain extension length. There are two kinds of waveform changes, which are mainly determined by the incident beam of the probe incident on the reflector.

angle.

Type 1.The probe beam is approximately perpendicular to the reflector, as shown in Figure C.3.When the probe is in any position, the A type is displayed as a single

Jagged echoes. When the probe moves, A sweeps back a significant ( >±6dB) random echo amplitude change. The main source of this phenomenon

Because the reflected echoes come from different faces of the reflector, or the reflected echoes of multiple faces are generated by random interference.

a) Probe position and echo amplitude variation for A-scan b) Typical example in the thickness direction c) Typical example in the length direction

Description.

1 ---A type scanning;

2 --- peak change;

3 --- reflector;

d --- the baseline range at the level;

H---the amplitude of the echo;

x --- Probe position.

Figure C.3 Waveform of the ultrasonic response 3

C.4 Waveform 4

The second type. the probe beam is obliquely incident on the reflector, and the waveform is “walking echo waveform”, as shown in Figure C.4.Probe at any position

At the same time, the peaks show fluctuations in multiple high points. The peak envelope is shown in a bell shape. When the probe moves, each peak changes in the envelope

Inside, and in turn rise to the maximum of the envelope centerline, and then fall to the noise level. All echo peaks will cause significant ( >±6dB)

Random fluctuations in amplitude.

a) Probe position and echo amplitude variation for A-scan b) Typical example in the thickness direction c) Typical example in the length direction

Description.

1 ---A type scanning;

2 --- echo envelope;

3 --- peak change;

4 --- reflector;

d --- the baseline range at the level;

H---the amplitude of the echo;

x --- Probe position.

Figure C.4 Waveform of the ultrasonic response 4

C.5 Waveform 5

The waveform of the dense reflector is shown in Figure C.5.When the probe is in any position, the A type shows a bundle-shaped echo. Within a certain range,

Dense echoes can sometimes resolve adjacent echoes, sometimes indistinguishable adjacent echoes. When the probe moves, the amplitude of the echo rises and falls randomly,

If adjacent echoes are discernible, each individual reflector signal can be found to reveal the waveform of waveform 1.

a) Probe position and echo amplitude variation for A-scan b) Waveform of the ultrasonic response in the thickness direction 5 c) Waveform of the ultrasonic response in the longitudinal direction 5

Description.

1 ---A type scanning;

2 --- Peak change.

Solid line. long range signal;

Dotted line. short range signal;

d --- the baseline range at the level;

H---the amplitude of the echo;

x --- Probe position.

Figure C.5 Waveform of the ultrasonic response 5 references

[1] GB/T 11345-2013 Non-destructive testing of welds Ultrasonic testing techniques, testing levels and assessment (ISO 17640.2010,

MOD)

[2] GB/T 29712-2013 Non-destructive testing of welds Ultrasonic testing acceptance level (ISO 11666.2010, MOD)

[3] ISO 11666 Non-destructivetestingofwelds-Ultrasonictesting-Acceptancelevels

GB/T 29712-2023 | GB/T 27552-2021 | GB/T 32260.1-2015 | GB/T 32259-2015 | GB/T 29713-2026 | […]