GB/T 37361-2019Determination of the film thickness - Ultrasonic thickness gauge method (English PDF)

Foreword

This standard was drafted in accordance with the rules given in GB/T 1.1-2009.

This standard uses the translation method equivalent to ISO /T S19397.2015 "Using ultrasonic thickness gauge to determine the film thickness of the coating".

The documents of our country that have a consistent correspondence with the international documents referenced in this standard are as follows.

---GB/T 5206-2015 Terms and definitions of paints and varnishes (ISO 4618.2014, IDT).

This standard has made the following editorial changes.

--- In order to coordinate with the existing paint film thickness measurement standard, the name was changed to "measurement of film thickness ultrasonic thickness gauge method".

This standard was proposed by the China Petroleum and Chemical Industry Federation.

This standard is under the jurisdiction of the National Coatings and Pigments Standardization Technical Committee (SAC/TC5).

This standard was drafted. Jiangsu Lanling Polymer Materials Co., Ltd., Guangzhou Synthetic Materials Research Institute Co., Ltd.

(Guangzhou) Co., Ltd., Zhejiang Yutong New Materials Co., Ltd., AVIC Baimu New Material Technology Engineering Co., Ltd., CNOOC Changzhou

Paint Chemical Research Institute Co., Ltd., Shenzhen Guangtian Environmental Protection Coating Co., Ltd., Hebei Chenyang Industry and Trade Group Co., Ltd., China Paint (Deep

Shenzhen) Co., Ltd., Baden Fu Industrial Co., Ltd., Shunde District, Foshan City, China Car Tangshan Locomotive & Rolling Stock Co., Ltd., Changzhou Guanghui Chemical Co., Ltd.

Division, Zhejiang Mingquan Industrial Coating Co., Ltd., Dongguan Enfeng Building Materials Technology Co., Ltd., Shaanxi Baotashan Paint Co., Ltd., Fujian Fu

Special Materials Co., Ltd.

1 Scope

This standard specifies a method for determining the film thickness of coatings on metal and non-metal substrates using ultrasonic thickness gauges.

2 Normative references

The following documents are indispensable for the application of this document. For dated references, only the dated version applies to this document.

For the undated references, the latest version (including all amendments) applies to this document.

ISO 4618 Paint and varnish terms and definitions (Paintsandvarnishes-Termsanddefinitions)

3 Terms and definitions

The following terms and definitions defined by ISO 4618 apply to this document.

3.1

Ultrasonic ultrasonicwave

Sound waves with a frequency higher than the hearing range of the human ear, usually with a frequency higher than 20 kHz.

[EN1330-4.2010, definition 3.1.1]

3.2

Longitudinal wave

Compressed wave compressionalwave

The vibration direction of the medium particle is the same as the wave propagation direction.

[EN1330-4.2010, definition 2.3.1]

3.3

Echo echo

Ultrasonic pulse reflected to the probe.

[EN1330-4.2010, definition 5.5.2]

3.4

Echo height echoheight

Echo amplitude echoamplitude

The echo (3.3) height displayed on the screen.

[EN1330-4.2010, definition 5.5.5]

3.5

Ultrasound pulse ultrasonicimpulse

Ultrasonic signal with short duration.

3.6

Ultrasonic sensor ultrasonicsensor

Ultrasonic probe ultrasonicprobe

A device for transmitting and receiving ultrasonic waves (3.1), mainly using piezoelectric materials.

3.7

Acoustic impedance acousticimpedance

The product of the density of the material and the speed of sound.

3.8

Reflection coefficient

The ratio of the total reflected sound pressure to the incident sound pressure at the reflecting surface.

[EN1330-4.2010, definition 3.4.11]

Note. The reflection coefficient R of the wave is calculated by the acoustic impedance (3.7) Z1 and the acoustic impedance (3.7) Z2 of the boundary medium, where 1 is the medium of the incoming sound.

R=

Z2-Z1

Z2 Z1

If the reflection coefficient is negative, change the phase (3.9) of the reflected signal by 180°.

3.9

Phase phase

A position of a complete wave period, expressed as an angle.

[EN1330-4.2010, definition 2.2.5]

3.10

Interface

Acoustic impedance (3.7) is the interface of acoustic contact between two different media.

[EN1330-4.2010, definition 3.4.1]

3.11

Sound propagation time soundpathtraveltime

The time it takes for the sound wave to travel along the path.

[EN1330-4.2010, definition 5.6.3]

3.12

Coupling agent couplant

Coupling film coupling film

A medium applied between the probe and the object to be measured so that the ultrasonic wave can pass smoothly.

[EN1330-4.2010, definition 5.3.2]

3.13

A scan shows A-scanpresentation

The ultrasonic signal is displayed, where the X axis is expressed in time and the Y axis is expressed in amplitude.

[EN1330-4.2010, definition 5.5.16]

Note. Ultrasonic film thickness measuring device, in addition to displaying the film thickness value, usually also displays A-scan for checking the echo form and echo sequence.

3.14

Calibration calibration

The first step in a set of operations under specified conditions is to determine the relationship between the magnitude provided by the measurement standard and the corresponding indication.

The quantity and the corresponding value provided by the quantity standard have measurement uncertainty. In the second step, through this information, you can know how to obtain the measurement from the indication value.

Quantity results.

Note 1. Calibration can be expressed in the form of an overview, calibration function, calibration chart, calibration curve or calibration table. In some cases, it can include

Correction of the indication of the degree of certainty, plus correction value or multiplication correction factor.

Note 2. Note that avoiding calibration is confused with calibration and calibration verification of measurement systems that are often referred to as "self-calibration".

Note 3. Usually, only the first step in the above definition is considered to be calibration.

[ISO /IEC Guide 99.2007, Definition 2.39]

3.15

Measurement system adjustment adjustmentofameasuringsystem

Adjustment adjustment

A series of operations performed on the measurement system so that the measuring instrument gives a specified indication corresponding to the value to be measured.

Note 1. The adjustment type of the measurement system usually includes zero adjustment of the measurement system, offset adjustment and range adjustment (sometimes called "gain adjustment").

Note 2. Pay attention to avoid confusion between adjustment and calibration of the measurement system (3.14), which is the premise of adjustment.

Note 3. After the measurement system is adjusted, it is usually necessary to recalibrate the measurement system.

[ISO /IEC Guide 99.2007, Definition 3.11]

3.16

Working standard workingstandard

Traceable to national standards.

[EN60731.2007, definition 3.4.1.2]

4 Principle

The method specified in this standard determines the thickness of a single coating by the propagation time of the ultrasonic pulse reflected at the interface of the coating system.

The advantages and disadvantages of this method can be seen from the data obtained from the combination of different coating substrates related to practical use.

5 Physical principles of measurement methods and applications

When measuring the film thickness using ultrasonic waves, longitudinal waves are used because the longitudinal waves are easy to generate and can be coupled to almost every liquid.

As shown in Fig. 1, the ultrasonic sensor (6) is composed of a piezoelectric disk and a "delay block" for generating and receiving sound waves.

The ultrasonic pulse first passes through the delay block and then through the first to third layers, directly to the substrate (1) and even further.

A part of the ultrasonic wave reaching each interface is reflected as a new ultrasonic pulse, and the other part is irradiated by the ultrasonic pulse.

On the 1st floor (4), the ultrasonic sensor will receive the first reflection.

Description.

1---substrate;

2---3rd floor;

3---layer 2;

4---first layer;

5---coupling agent (liquid);

6---ultrasonic sensors (transmitters and receivers);

E---Echo layer, 1, 2, 3.

Figure 1 Ultrasonic method

The ultrasonic pulse is recorded after being received by the ultrasonic sensor. In three separate layers, the duration between the ultrasonic pulses

The acoustic path propagation time Ti (i = 1, 2, 3). The amplitude or echo height of the ultrasonic pulse reflected at each interface depends on the respective

Reflection coefficient. If the speed of sound in each layer is known, the film thickness can be calculated using the propagation time. For each layer, calculate according to equation (1).

v=

Td

T/2

(1)

In the formula.

v --- sound speed;

Td --- dry film thickness;

T --- sound path propagation time (back and forth) in this layer.

In order to be able to use the naked eye to resolve echoes with shorter acoustic propagation time intervals (for example, the propagation time in a coating with a thickness of 20 µm is

20ns), the ultrasonic pulse should be at least as short. To this end, the ultrasonic frequency should be high (at least the reciprocal of half of the propagation time), or

A-scan should be generated at a lower frequency by digital signal processing. See Figure 2 for an example of A-scan.

When the coatings are too thin, the echoes generated by the layers will fuse with each other. In this case, the evaluation is performed by the A-scan display.

The method is no longer applicable.

180°. If this is ignored, a relative time delay of half wavelength may occur.

The premise that the amplitude of the signal formed by the ultrasonic pulse on the two-layer interface is sufficiently high is.

---High enough reflection coefficient or different acoustic impedance Z;

--- There is a clear intersection between the materials.

Otherwise, the reflection may become too weak to detect. This can also happen on curved workpieces, due to geometrical reasons, not

Some parts of the sound wave can be transmitted back to the sensor from the interface at the same time.

Description.

T --- sound transmission time of layers 1, 2, and 3;

E --- Echo layer 1,2,3.

Figure 2 Example of A-scan display

6 Equipment and materials

7 Calibration, adjustment and inspection of measuring equipment

8 Determination steps

Operate the device according to the information provided by the manufacturer.

Note. Appendix A gives a description of the qualifications of the operator.

Apply some coupling agent to the coating and measure its film thickness. Place the sensor vertically on the coating and press it to make the film of the coupling agent change.

Keep it as thin as possible. Keep the probe in the measurement position until a stable measurement is displayed.

9 Measuring the effect of temperature

Most probes have a temperature range of -20 ° C to 60 ° C. However, it is recommended to perform ultrasonic film in the range of common ambient temperatures.

Thickness measurement to maintain the test object during measurement, couplant and probe at equilibrium temperature. Delay block or test object in the probe

The temperature gradient in the temperature causes uncontrollable changes in the speed of sound and fluctuations that affect the measurement results.

In all materials, the speed of sound is more or less related to temperature.

Note. For polymers, the negative temperature coefficient usually varies from 0.1% to 0.3% per degree Celsius.

In order to minimize errors due to temperature changes, measurements should be made under constant temperature conditions. Adjustments and subsequent measurements

The amount should be carried out at the same temperature. In the case of measuring long-term interruption and changes in ambient temperature, the adjustment should be checked.

10 precision

11 test report

The test report shall include at least the following.

a) identify all the necessary details necessary for the test product;

b) indicate the standard number;

c) test results;

d) any deviation from the specified test method;

e) any anomalies that occur during the measurement;

f) Test date.

Appendix A

(informative appendix)

Personnel qualification

The operator who performs ultrasonic thickness measurement according to this standard shall introduce the physical principle and measurement process of the method to the operator.

And before the test should have the operating experience under the guidance of this type of personnel.

For untested coating systems, the operator should be provided with information about the product and the material to be tested. In order to reliably set up the device,

To understand the physical principles of ultrasound and a detailed understanding of the metrology process. Know the most common ultrasound thickness due to the similarity of metrology work.

Degree measurement methods are helpful (see references).

Appendix B

(informative appendix)

Precision determination

B.1 Summary of information on rotation tests between laboratories

Perform a rotation test between laboratories to determine the precision of film thickness measurement using an ultrasonic film thickness measuring device. Five units participated

This rotation test.

B.2 sample

For the rotation test, an aqueous standard dispersion was applied to ten different substrates (see Table B.1). The dispersion was repeated

Apply to some of the substrates to achieve a higher film thickness.

Five test samples were prepared for each type of substrate for each film thickness.

The film thickness of the wood sample is 100 µm.

For other types of substrates, test samples with film thicknesses of 22 µm and 44 µm were prepared.

In order to perform the basic calibration, it is necessary to prepare additional calibration plates with the same parameters and cross-sectional areas for the beam splitting microscope.

In order to directly compare the measurement of the film thickness by microscopy/ultrasonic method, it is also necessary to prepare some other cross-sectional areas for the beam splitting microscope.

Test board.

Table B.1 Corresponding film thicknesses on substrates and substrates used in the rotation test

Nominal film thickness/µm

Spruce veneer plywood 100

Polished spruce 100

Elm veneer plywood 100

Polished eucalyptus 100

Aluminum 22

Aluminum 44

Tree root wood 44

Carbon fiber composite 22

Carbon fiber composite 44

PP (polypropylene) 22

PP (polypropylene) 44

SMC (sheet molding compound) 22

SMC (sheet molding compound) 44

Steel 22

Steel 44

B.3 Ultrasonic film thickness measuring device

5 different ultrasonic film thickness measuring devices with frequency range greater than.200MHz for rotation test. Frequency below.200MHz

The equipment is not suitable for all substrates.

All equipment must be calibrated according to the information provided by the manufacturer prior to measurement.

B.4 Repeat measurement

Three measurements were taken for each sample.

Mark 3 measurement points on each sample.

B.5 Evaluation

B.5.1 General

The measurement results were evaluated according to ISO 5725-2 and ISO /T R22971.

The test sample root wood was identified as an anomalous material and was therefore ignored in the calculation of ultrasonic accuracy.

The repeatability and reproducibility of each substrate and film thickness were calculated separately (see Table 1 and Table 3).

Since the various wood types and the repeatability and reproducibility of aluminum and steel are similar, a simplified test group is formed and they are calculated

Repetitive and reproducible.

B.5.2 Repeatability

Figures B.1, B.2 and B.3 show the plots for each set of samples.

--- Wood samples with a film thickness of 100 µm (see Figure B.1);

--- Aluminum, carbon fiber composites, PP, SMC and steel samples, film thickness of 22µm (see Figure B.2) and 44µm (see Figure B.3).

Description.

Y --- film thickness, µm;

X --- substrate;

1 --- spruce veneer plywood;

2 --- polished spruce;

3 --- eucalyptus veneer plywood;

4 --- polished eucalyptus;

[ ] --- average value;

--- Confidence interval of mean +/- 0.95;

---Minimum Maximum.

Figure B.1 Repeatability of wood samples with a film thickness of 100 µm

Description.

Y --- film thickness, µm;

X --- substrate;

1 --- aluminum;

2 --- carbon fiber composite;

3 ---PP (polypropylene);

4 ---SMC (sheet molding compound);

5 --- steel;

[ ] --- average value;

--- mean +/- 0.95 confidence interval;

---Minimum Maximum.

Figure B.2 Repeatability of other samples with a film thickness of 22 µm

Description.

Y --- film thickness, µm;

X --- substrate;

1 --- aluminum;

2 --- carbon fiber composite;

3 ---PP (polypropylene);

4 ---SMC (sheet molding compound);

5 --- steel;

[ ] --- average value;

--- mean +/- 0.95 confidence interval;

---Minimum Maximum.

Figure B.3 Repeatability of other samples with a film thickness of 44 µm

The repeatability limit (r) for each sample (see Table 1) is calculated based on 3 measurements for each substrate and each film thickness.

The repeatability limits (r) for wood and metal product groups (see Table 2) are basically consistent with the repeatability values of individual tests.

B.5.3 Reproducibility limits

The reproducibility limit (R) of each sample was calculated from all measured film thickness values (see Table 3).

Compared with the results of a single sample, the reproducibility limit (R) of the wood and metal sample sets (see Table 4) is more variable.

B.5.4 Influencing factors

The calculation of repeatability ...