Absorbing Coating Thickness Measurement

In modern aerospace field, the thickness measurement of absorbing coating is a crucial technical link. Absorbing coating can not only effectively absorb electromagnetic waves, but also improve the stealth performance of aircraft. However, due to the material characteristics and thin thickness of absorbing coating, traditional measurement methods often difficult to meet the accuracy requirements. Today we will combine the practical case of absorbing coating sample, introduce how to use ultrasonic thickness gauge, through high precision measurement means to solve the problem of absorbing coating thickness measurement.

Background

Absorbing coating is a special material that can absorb electromagnetic waves, usually coated on the surface of metal or non-metallic substrates. Due to its unique electromagnetic properties, absorbing coatings are widely used in stealth technology, electromagnetic shielding and other fields. However, the thickness of absorbing coatings is usually thin (0.3-1.2mm), and the material itself has complex acoustic properties, which brings great challenges to thickness measurement.

As a non-destructive testing method, ultrasonic thickness measurement technology can accurately measure coating thickness without damaging the material. By selecting appropriate probes and instrument parameters, ultrasonic thickness gauge can effectively deal with various difficulties in measuring absorbing coatings and ensure the accuracy and reliability of measurement results.

 Sample Show

The sample we received this time is an absorbing coating covered on a non-metallic substrate with thickness about 0.58mm. Our customer hopes that we can use an ultrasonic thickness gauge to measure the thickness of the absorbing coating.

The absorbing materials we come into contact with are basically metal substrates. For example, we once received a measurement request from an aviation unit to measure the thickness of the absorbing coating on the surface of the aircraft. The absorbing coating on aircraft surface is usually coated on a metal substrate (such as steel plate, aluminum plate, titanium plate), the substrate thickness is about 2mm.

However, the acoustic properties of non-metallic substrates are significantly different from those of metal substrates:

Lower sound velocity - The sound velocity of non-metallic materials is usually lower than that of metals, which affects the time of ultrasonic propagation and the reception of the echo signals.

Small acoustic impedance difference - The small acoustic impedance difference between the non-metallic substrate and the absorbing coating may cause the interface echo signal weak and difficult to clearly identify.

High signal attenuation - Non-metallic materials usually have a large attenuation on ultrasonic waves, especially when the absorbing coating itself has high attenuation characteristics, the signal penetration ability will be further reduced.

Measurement Solution

For the thickness measurement of the absorbing coating on the metal substrate, the measurement solution we provided was to use YUSHI PM5 Gen2 ultrasonic thickness gauge with a 5MHZ 13mm delay line probe, solved customer's needs very well.

We can still use PM5 Gen2 to solve the measurement difficulties of the absorbing coating on the non-metallic substrate.

Choose the Appropriate Probe

For the absorbing coating on the non-metallic substrate, we selected the D5A6 delay line probe. This probe has high resolution and high sensitivity, which can effectively deal with the problem of absorbing coating signal attenuation and capture the echo signal of thin coating.

Adjust the Instrument Parameters Correctly

PM5 Gen2 has a variety of parameter adjustment functions (such as blanking, E-blanking, phase, gate, etc.), which can lock the correct waveform to ensure the accuracy of the measurement results.

Gain adjustment: Increase the gain appropriately to enhance the reception of weak signals, but pay attention to avoid noise interference.

Blanking and E-blanking: By adjusting the blanking parameters, unnecessary clutter can be hidden to ensure that the instrument can correctly identify the interface echo between the coating and the substrate.

Gate setting: Reasonably set the gate position to lock the interface echo between the coating and the substrate to ensure the accuracy of the measurement results.

 Measurement Process

The sample was measured using PM5 Gen2 with D5A6 delay line probe, and gel couplant was used to enhance the propagation of ultrasonic waves. Adjust Gain, Blank, E-Blan, Gate, Range and other parameters to determine the interface echo between the coating and the substrate, and the sound velocity was calibrated with the known coating thickness, and then the thickness of other parts was verified.

Summarize

The application of ultrasonic thickness gauge in the measurement of absorbing coating thickness can not only accurately measure the thickness of the coating without damaging the material, but also provide powerful technical support for the development and application of absorbing coatings. By selecting high-performance ultrasonic thickness gauge (such as PM5 Gen2) and high-resolution probes (such as D5A6 and D5A13 delay line probes), we can effectively deal with various difficulties in measuring absorbing coatings on non-metallic substrates and metal substrates, ensuring the accuracy and reliability of the measurement results.

If you encounter similar problems in measuring absorbing coatings, or want to learn more about the application of ultrasonic thickness measurement technology, please contact us, we will provide you with professional solutions and technical support.