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GB/T 20935.2-2018: Metal materials -- Method of electromagnetic acoustic inspection -- Part 2: Standard practice for ultrasonic testing using electromagnetic acoustic transducer (EMAT) techniques
Status: Valid GB/T 20935.2: Evolution and historical versions
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| GB/T 20935.2-2018 | English | 359 |
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Metal materials -- Method of electromagnetic acoustic inspection -- Part 2: Standard practice for ultrasonic testing using electromagnetic acoustic transducer (EMAT) techniques
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GB/T 20935.2-2018
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| GB/T 20935.2-2009 | English | 714 |
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Metho`1d of electromagnetic acoustic inspection for metal materials -- Part 2: Standard practice for ultrasonic testing using electromagnetic acoustic transducer (EMAT) techniques
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GB/T 20935.2-2009
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Basic data | Standard ID | GB/T 20935.2-2018 (GB/T20935.2-2018) | | Description (Translated English) | Metal materials -- Method of electromagnetic acoustic inspection -- Part 2: Standard practice for ultrasonic testing using electromagnetic acoustic transducer (EMAT) techniques | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | H26 | | Classification of International Standard | 77.040.20 | | Word Count Estimation | 18,123 | | Date of Issue | 2018-03-15 | | Date of Implementation | 2018-12-01 | | Issuing agency(ies) | State Administration for Market Regulation, China National Standardization Administration | GB/T 20935.2-2018: Metal materials -- Method of electromagnetic acoustic inspection -- Part 2: Standard practice for ultrasonic testing using electromagnetic acoustic transducer (EMAT) techniques
---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Metal materials--Method of electromagnetic acoustic inspection--Part 2. Standard practice for ultrasonic testing using electromagnetic acoustic transducer(EMAT)techniques
ICS 77.040.20
H26
National Standards of People's Republic of China
Replace GB/T 20935.2-2009
Electromagnetic ultrasonic testing method for metal materials
Part 2. Using electromagnetic ultrasonic transducers
Technique for ultrasonic testing
Part 2. Standardpracticeforultrasonictestingusingelectromagneticacoustic
Published on.2018-03-15
2018-12-01 implementation
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
China National Standardization Administration issued
Content
Foreword III
1 Scope 1
2 Normative references 1
3 Terms and Definitions 1
4 Principle Overview 1
5 Meaning and use 4
6 Application conditions 5
7 equipment 5
8 check 11
9 Detection method 12
10 result judgment 13
11 Test report 13
Foreword
GB/T 20935 "Electromagnetic Ultrasonic Testing Method for Metal Materials" is divided into the following three parts.
--- Part 1. Guide to electromagnetic ultrasonic transducers;
--- Part 2. Methods for ultrasonic testing using electromagnetic ultrasonic transducer technology;
--- Part 3. Ultrasonic surface detection using electromagnetic ultrasonic transducer technology.
This part is the second part of GB/T 20935.
This part is drafted in accordance with the rules given in GB/T 1.1-2009.
This part replaces GB/T 20935.2-2009 "Electromagnetic Ultrasonic Testing Methods for Metallic Materials - Part 2. Using Electromagnetic Ultrasonic Transducers
The method of technology for ultrasonic testing", compared with GB/T 20935.2-2009, the main technical changes are as follows.
--- The items in the scope were merged, and the original standard "1.7 This part is based on international units as standard units" and "1.8 parts"
Do not discuss security issues related to use. It is the responsibility of the user to establish procedures for the safety and health of the person before use.
Set its scope of application. (see Chapter 1,.2009 editions 1.7 and 1.8);
--- Revised the normative reference document (see Chapter 2, Chapter 2 of the.2009 edition);
--- Amend the qualification requirements of Chapter 6 to "If the contract requires, the personnel performing this part of the inspection should be obtained by the relevant department.
Technical qualifications identified in GB/T 9445 or equivalent standards and authorized by the employer. Standard for the basis of qualification (including version number)
It should be stated in the contract. " (see 6.1,.2009 edition 6.1).
This part was proposed by the China Iron and Steel Association.
This part is under the jurisdiction of the National Steel Standardization Technical Committee (SAC/TC183).
This section drafted by. Iron and Steel Research Institute, Steel Research Institute Testing Technology Co., Ltd., Metallurgical Industry Information Standards Institute.
The main drafters of this section. Zhang Jianwei, Fan Hong, Liu Tao, Xu Lei, Liu Guanglei, Shen Haihong, Dong Li.
The previous versions of the standards replaced by this section are.
---GB/T 20935.2-2009.
Electromagnetic ultrasonic testing method for metal materials
Part 2. Using electromagnetic ultrasonic transducers
Technique for ultrasonic testing
1 Scope
This part of GB/T 20935 gives an overview and significance of the principle of using ultrasonic ultrasonic transducer (EMAT) for specific ultrasonic testing.
And use, and specify the application conditions, equipment, calibration, testing methods, results determination and test reports.
This section is applicable to users who think that the electromagnetic ultrasonic transducer technology is superior to the traditional piezoelectric technology; it is not suitable for traditional technology.
More advantageous occasions.
This section applies to all materials that can generate sound waves by electromagnetic methods, including ferromagnetic or non-ferromagnetic metal materials.
Note. This section describes the application of some proven electromagnetic ultrasonic transducer technology, but does not mean that these technologies are the best or only, only provide one
The choice of some applications.
2 Normative references
The following documents are indispensable for the application of this document. For dated references, only dated versions apply to this article.
Pieces. For undated references, the latest edition (including all amendments) applies to this document.
GB/T 9445 Non-destructive testing personnel qualification and certification
GB/T 11344 non-destructive testing contact ultrasonic pulse echo method for thickness measurement
GB/T 12604.1 Non-destructive testing terminology ultrasonic testing
GB/T 12604.6 Non-destructive testing term eddy current testing
GB/T 20935.1 Electromagnetic Ultrasonic Testing Methods for Metallic Materials - Part 1. Guide to Electromagnetic Ultrasonic Transducers
GB/T 23900 Non-destructive testing material ultrasonic speed measuring method
3 Terms and definitions
The terms and definitions defined in GB/T 12604.1, GB/T 12604.6 and GB/T 20935.1 apply to this document.
4 Principles Overview
4.1 Surface inspection
4.1.1 Surface waves excited in the material being tested can detect surface discontinuities sensitively, which is reflected back through the discontinuous interface.
Wave or transmission wave attenuation to sense discontinuity, that is, pulse reflection technology or one-shot technology.
4.1.2 A typical electromagnetic ultrasonic transducer that excites surface waves or lamb waves is shown in Figure 1. The applied external magnetic field B0 is parallel to the non-ferromagnetic
Or the surface of the ferromagnetic material, the fold-back coil is placed in parallel on the surface of the material and is pulsed with radio frequency (RF) electric pulses, which are generated on the surface of the material by induction.
Current, surface current is affected by Lorentz force in the magnetic field, and Lorentz force excites stress waves perpendicular to the surface vibration of the material to generate surface
wave. Electromagnetic ultrasonic transducers generally produce bidirectional surface waves, and special designs can also produce the same unidirectional waves as conventional ultrasonic testing.
Description.
1 --- foldback coil;
2 --- surface acoustic wave pulse;
B0---additional magnetic field;
FL---Lorentz force.
Figure 1 Typical electromagnetic ultrasonic transducer producing surface waves or Lamb waves
4.1.3 Surface discontinuities can cause reflection or attenuation of surface waves. Reflected or attenuated ultrasound near the electromagnetic ultrasonic transducer receiving coil
The wave causes the conductor placed in the magnetic field to vibrate, thereby inducing a measurable voltage in the coil.
4.2 Internal testing
4.2.1 In order to discover discontinuities within the material, ultrasonic bulk waves should be used for testing. Same principle as surface inspection, internal inspection
The discontinuity is perceived by the reflected echo or transmitted wave attenuation of the discontinuous interface.
4.2.2 P-wave or shear wave detection can be selected depending on the object. Although the direct beam pulse reflection method is the most intuitive, but based on the position of the discontinuity
It may be more desirable to select the oblique beam bundle one-shot technique for factors such as orientation and orientation.
4.2.3 A typical electromagnetic ultrasonic transducer device for exciting body waves is shown in Fig. 2. The applied external magnetic field B0 is perpendicular to non-ferromagnetic or ferromagnetic
On the surface of the material, the spiral flat coil is placed in parallel on the surface of the material and is pulsed, and current is generated on the surface of the material by induction.
The current is subjected to Lorentz forces in the magnetic field, creating a vibrational stress wave on the surface of the material. Depending on the direction of the magnetic field, it can be excited perpendicular to the workpiece
The surface propagates a radially polarized shear wave or a plane polarized transverse wave. The device of Figure 2 excites a radially polarized transverse wave. Can also be used in non-ferromagnetic materials
The longitudinal wave that can be used is excited; in the ferromagnetic material, it is difficult to excite the longitudinal wave because the coupling efficiency is extremely low. Internal detection can be used
Longitudinal waves obtained by over-wavelength conversion. 7.2 Detailed description of electromagnetic ultrasonic transducers and magnetizing devices that excite various modes of body waves.
Description.
1---magnet;
2---spiral coil;
3---J (eddy current);
4---FL (Lorentz Force);
5---B0 (magnetic field);
6---ultrasonic;
7---tested workpiece;
8---Top view.
Figure 2 Typical electromagnetic ultrasonic transducer producing body waves
4.3 Thickness measurement
4.3.1 After the ultrasonic wave is transmitted into the material, it is reflected back to the surface at the bottom surface. When the sound velocity is known, the time of sound wave propagation is measured to calculate the material.
The thickness of the material. For known materials, the thickness of the material can also be extrapolated based on the propagation time of the standard thickness test block. For the test method, see
GB/T 11344.
4.3.2 The speed of ultrasonic propagation in a material depends on the physical properties of the material, ie the stiffness and density of the material. For known types of materials
It is generally considered that its physical properties are a constant. The approximate speed value can be found in many materials, and can also be passed in accordance with GB/T 23900.
Get it.
4.3.3 Body waves should be used to determine the propagation time of sound waves in the material. Although longitudinal waves can be used, transverse waves should generally be used, which is due to
The shear wave travels slowly in the material and is more accurate for thinner materials. Although the straight beam pulse echo method is the simplest and most commonly used,
However, when measuring thinner materials, if the scanning speed is required to be faster or the resolution is higher, it may be more desirable to use the oblique beam one-shot technique.
Methods for exciting body waves using electromagnetic ultrasonic transducer technology are discussed and described in 4.2.3 and Figure 2.
5 Meaning and use
5.1 Since the electromagnetic ultrasonic transducer is non-contact, it can be used for automatic detection, high-speed detection, dynamic detection, long-distance or hazardous environment.
The following detection, detection under high temperature conditions and detection under rough surface conditions. This section contains surfaces and surfaces using electromagnetic ultrasonic transducers.
Internal flaw detection and method of thickness measurement.
5.2 The uniqueness of electromagnetic ultrasonic transducer technology is reflected in the transmission and reception of ultrasonic waves. In addition, traditional ultrasonic testing techniques and methods
Both are suitable for electromagnetic ultrasound.
5.3 The electromagnetic ultrasonic transducer can detect non-ferromagnetic or ferromagnetic metals by electromagnetically exciting and receiving sound waves in the material.
material. The coil is the simplest device that the electromagnetic ultrasonic transducer excites the ultrasonic wave, and it is connected to the alternating current and placed on the surface of the material.
In the field, eddy currents are induced in the conductor. The eddy current is subjected to Lorentz forces in the magnetic field and collides with the metal lattice or other microscopic processes
Transfer the force to the material being tested. The direction of the Lorentz force alternates with the frequency of the excitation current, producing an ultrasonic wave. In ferromagnetic materials, the same
There is another coupling mechanism that excites the ultrasonic wave, that is, the dynamic magnetic field generated by the alternating current and the material magnetization field due to the hysteresis effect.
The interaction forms another wave source. Both of the above conversion mechanisms are reversible, so detection can be achieved. Figure 3 shows the excitation current
Magnetic ultrasonic conversion mechanism, force and direction.
a) b) c)
Description.
J --- current in a single conductor in amps (A);
B0 --- External magnetic induction intensity, the unit is Tesla (T);
Fm --- magnetizing force (ferromagnetic material), the unit is Newton (N);
Fms---Magnetostrictive force (ferromagnetic material), the unit is Newton (N);
FL --- Lorentz force (conductor material) in Newtons (N).
Figure 3 Electromagnetic ultrasonic generation mechanism
5.4 Electromagnetic ultrasonic transducers can excite ultrasonic waves in various modes. As with traditional ultrasonic testing, the choice of beam angle and sonic mode
It should be determined by the material, the possible position and orientation of the discontinuity. In order to correctly select the mode, you should know the geometry of the workpiece being inspected and
The approximate position, size, orientation, and reflectivity of the discontinuity are expected, and the range of lift-off and ultrasonic transmission allowed by the electromagnetic ultrasonic transducer should also be known.
The physical laws of broadcasting.
5.5 For applications requiring flexible selection of modes, electromagnetic ultrasonic transducer technology is significantly comparable to conventional piezoelectric ultrasound technology.
Advantage. Electromagnetic ultrasonic transducers can efficiently generate surface waves and are more prone to horizontally polarized transverse waves (SH) than conventional piezoelectric ultrasonic probes.
wave). The SH wave does not undergo waveform conversion at the interface and its incident angle can be varied from 0° to 90° by adjusting the transmission frequency.
The point is very important. Electromagnetic ultrasonic transducers can also excite lamb waves, which can be used for circumferential inspection of tubes or for overall inspection of sheets. electromagnetic
Ultrasonic transducers can be easily reproducible and have good interchangeability, so the signal response is very reproducible.
6 Application conditions
6.1 Staff qualifications
If the contract requires, the personnel performing the tests in this part shall obtain the technical assets identified by the relevant departments according to GB/T 9445 or equivalent standards.
Grid, and authorized by the employer. The criteria for the qualification basis (including the version number) should be stated in the contract.
6.2 Methods and techniques
The methods and techniques recommended in this section should be used unless specifically specified. The specially designated technology shall be indicated in the contract between the parties.
6.3 Report content and acceptance criteria
Unless otherwise stated, the test report shall be consistent with the requirements of Chapter 11. The acceptance criteria shall comply with the relevant standards or in the contract between the parties.
It is prescribed.
6.4 Re-examination after repair and rework
This section does not include the re-examination clause after repair and rework, and if necessary, it can be explained in the contract between the two parties.
7 equipment
7.1 Surface inspection
7.1.1 Base metal testing
7.1.1.1 Coil design
Figure 4 shows a typical refraction coil that produces surface waves, which can be pulse-reflective or one-shot.
Description.
1---magnet;
2---EMAT retraction coil structure diagram;
3---Typical EMAT foldback coil.
Figure 4 Typical electromagnetic ultrasonic transducer reflex coil that produces surface waves
7.1.1.2 Coil excitation
A dedicated high-power RF transmit circuit should be used to excite the coil in a periodic pulse train.
7.1.1.3 Magnetization of the workpiece
Figure 5 shows a typical magnetizing device that provides an external magnetic field for the folded-back coil, which produces a pulse parallel to the surface to be inspected.
The pulsing magnetic field, the pulse generator and its power source provide a pulse current to excite the pulse magnet. The magnetic field can also be from a permanent magnet or a DC electromagnet
provide.
Description.
1---steel plate;
2---magnetic core;
3---surface wave generator;
4---pulse magnetization coil;
5---electromagnetic ultrasonic transducer coil;
6---Magnetic flux.
Figure 5 Typical electromagnet structure for generating surface waves
7.1.1.4 Instruments
The instrument is used to acquire and analyze the signal from the electromagnetic ultrasonic transducer, and the circuit for signal processing and data acquisition is the receiving unit.
Gain adjustment and filtering of the signal is the same as for conventional ultrasound instruments. The instrument has a variety of acquisition and analysis signals available.
Operator selection. The computer is equipped with an A/D conversion board and corresponding ultrasonic flaw detection software to form an effective configuration. Can also be used with tradition
A simple, simple configuration of the ultrasound system sends an analog signal to the oscilloscope to display the test results. In addition, in order to provide accurate touch to the signal acquisition
The pulse generator/receiver synchronization circuit should be used.
7.1.1.5 Comparative sample
The comparative specimen used for the calibration equipment shall have the same material, thickness, surface condition and heat treatment state as the material to be inspected. Comparative sample
In addition to the artificial injury used to adjust the sensitivity, there should be no discontinuity affecting the normal indication of artificial injury. Length and width of artificial injury
And depth should be consistent with the acceptance criteria.
7.1.2 Weld inspection
7.1.2.1 Coil design
In most cases, the electromagnetic ultrasonic transducer coils and magnets used to test the parent metal (see 7.1.1) can be used for weld inspection. However in some situations
Under the circumstance, the detection of the discontinuity of the weld surface is difficult because the root and the residual height of the weld may produce reflection, and sometimes the reflection is strong.
So as to be confused with the discontinuity signal, even drowning the discontinuity signal. Diffraction technology can be used to eliminate the reflection signal of the weld structure
Clearness shows discontinuity. Figure 6 shows a specially designed electromagnetic ultrasonic transducer probe with one shot and one focus line coincident.
At an angle to the centerline of the weld, the appropriate frequency is chosen such that the surface wave wavelength is comparable to the discontinuity of the near surface of the workpiece being tested.
The discontinuity can be detected by wide angle diffraction, while the root and residual signal of the weld are reflected in specular reflection and are not received by the coil.
Figure 6 Electromagnetic ultrasonic transducer coils that produce surface wave focal line coincidence
7.1.2.2 Coil excitation
Should comply with the provisions of 7.1.1.2.
7.1.2.3 Magnetization of the workpiece
Figure 5 shows a magnetizing device that provides an external magnetic field for the 7.1.2.1 coil, which produces a pulsed magnetic field parallel to the surface to be inspected.
field. The magnetic field can also be provided by a permanent magnet or a direct current electromagnet.
7.1.2.4 Instruments
Should comply with the provisions of 7.1.1.4.
7.1.2.5 Comparative sample
The comparison sample should meet the following requirements.
a) The comparative specimen used for the calibration equipment shall have the same material, welding magnetic properties, thickness, surface condition and heat from the object to be inspected.
The weldment of the treatment state is intercepted. In addition to the artificial injury used to adjust the sensitivity on the comparison sample, there should be no influence on the artificial injury.
Often indicated discontinuities exist. A comparative artificial injury should be made in the weld zone to ensure that the specified sensitivity is achieved. Artificial injury is usually
Grooved or flat bottom holes.
b) Artificial injuries can be made on the weld, in the heat affected zone of the weld (ie parallel to the base metal of the weld), or in accordance with the welding acceptance criteria
Provisions.
c) The length, depth and width of the groove shall be determined by the user and shall be consistent with the welding acceptance criteria.
d) Groove depth is the value from the edge of the groove to the deepest and shallowest. Measuring groove depth can be optical, complex, mechanical or other
law. The groove depth is usually defined as a percentage of the nominal thickness.
7.2 Internal inspection
7.2.1 Base metal testing
7.2.1.1 Coil design
Internal inspection is the use of body waves to detect the inside of the material. Figure 7 shows various electromagnetic ultrasonic transducer coils capable of exciting body waves and
In the form of a magnet. As with traditional ultrasonic testing, the mode of operation can be either pulsed or one-shot. Coil by RF pulse
The excitation is based on the magnetic field that is parallel or perpendicular to the surface of the material, depending on the desired mode.
Description.
1---SV transverse wave;
2---SV transverse wave or oblique longitudinal wave;
3---folding coil;
4---radially polarized transverse wave;
5---SV transverse wave;
6---spiral coil;
7---radially polarized transverse wave;
8---SH shear wave or SH shear guide wave;
9---spiral coil.
Figure 7 Typical electromagnetic ultrasonic transducer coil/magnet form used to excite body waves
7.2.1.2 Coil excitation
A dedicated high power RF generator is used to excite the coil. For a folded-back coil, the excitation signal is a pulse train of several cycles;
Rotating the coil, the excitation signal is a sharp pulse or a short pulse train.
7.2.1.3 Instruments
Should comply with the provisions of 7.1.1.4.
7.2.1.4 Comparative sample
Should comply with the provisions of 7.1.1.5.
7.2.2 Weld inspection
7.2.2.1 Coil design
The electromagnetic ultrasonic transducer coil used for internal inspection of the weld is substantially the same as the coil internally detected by the base material. Electromagnetic ultrasound shown in Figure 7
The transducer coil/magnet is also suitable for internal inspection of welds. The working mode can be pulse-reflective or one-shot, and the coil is made of RF pulse.
The excitation is based on the selected mode, and the direction of magnetization is parallel or perpendicular to the surface of the workpiece.
7.2.2.2 Coil excitation
Should comply with the provisions of 7.1.1.2.
7.2.2.3 Instruments
Should comply with the provisions of 7.1.1.4.
7.2.2.4 Comparative sample
Should comply with the provisions of 7.1.2.5.
7.3 Thickness measurement
7.3.1 Thin workpiece
7.3.1.1 Coil design
The following electromagnetic ultrasonic transducer method is suitable for measuring workpieces with a thickness of 2.54 mm to 12.7 mm, especially for rough surfaces.
Workpiece.
Figure 8 shows an electromagnetic ultrasonic transducer coil for measuring the thickness of a thin workpiece, which is a one-piece integrated structure. It is incident on the workpiece with a transverse wave.
Receives the longitudinal wave reflected from the bottom surface. The coil is excited by a sharp pulse and a large current. This method has many advantages over the typical pulse reflection method.
The delay caused by the oblique wave and the waveform-converted longitudinal wave reduces or eliminates a series of problems caused by the excessive primary pulse of the primary reflected wave.
Low frequencies (about 1 MHz) are also allowed, and the low frequencies are not sensitive to bottom irregularities. When the bottom surface is irregular (such as a steam distribution pipe), use
The method uses one echo to get accurate measurements.
Figure 8 Shape of the receiving/transmitting electromagnetic ultrasonic transducer coil for thin workpiece thickness measurement
7.3.1.2 Coil excitation
A dedicated high power RF generator is used to excite the coil. The excitation signal is a sharp pulse or a short pulse train.
7.3.1.3 Magnetization of the workpiece
Figure 5 shows a pulsed electromagnet used to provide a magnetic field to the coil described in 7.3.1.1. The pulse electromagnet is in the workpiece table to be inspecte...
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