Everything You Need to Know About Ultrasonic Transducers

by Vivian M Knapp

An ultrasonic transducer is used to measure parameters using sound waves in high frequency.

Ultrasonic transducers are used by inspectors for various industrial applications like weld inspection, thickness gaging, as well as flaw detection.

They typically come in various sizes, shapes, types, and so on. Because of these varieties, someone new to it all may find it a bit confusing. To help eliminate this confusion, we will be discussing everything you need to know about ultrasonic transducers in this article. We will start first by defining what they are.

Ultrasonic Transducer – What exactly is it?

Ultrasonic transducers are very important when it comes to ultrasonic tests. They are systems that can create as well as collect ultrasonic vibrations. They are used in nondestructive testing, here, electrical energy pulses are transformed to mechanical energy according to the sound waves type moving inside the test item.

The transducer works like an ultrasonic microphone and speaker that recovers and produces sound waves in frequencies that are higher than what the human ears can hear.

Industrial Ultrasonic Transducer – Types

The following are the types of this device used industrially:

1. Contact

As you can tell from the name, transducers that fall under this category are used for inspections that involve direct contact. It has just one element and a surface resistant to wear which makes it suitable for making contact with metals.

Contact transducers typically come in several configurations and styles. Inspectors make use of them for the following:

  • Measuring velocity
  • Inspecting bars, billets, plates, as well as other nonmetallic and metallic parts
  • Detecting flaw in straight beams
  • Thickness gaging

2. Dual Element

This type of transducer has 2 crystal elements inside one case. One acoustic barrier is used to separate the crystal elements. While one element serves as the receiver, the other produces sound waves.

Its workings are quite simple; the 2 elements are placed to face one another to form a sound path shaped like V in the material. They then receive and transmit beams across the material’s examination surface. Ultimately, this forms an effect with a sort of pseudo-focus; this then enhances the focal resolution.

The effect that is created is particularly useful when examining parts whose surfaces are rough backwall. This makes dual element transducers the standard ones used for measuring wall thickness during corrosion applications.

It is also used for other applications including:

  • High temperature
  • Detecting cracks in bolts
  • Detecting cracks, laminations, inclusions, and porosity in forgings and castings
  • Cladding bond and disband inspection and weld overlay

3. Immersion

These have just one element and are made to work underwater. Instead of making contact directly with the material being tested, an immersion transducer uses a column to receive sound energy to the material.

With this technique, parts can be scanned quickly and efficiently. Performance and sensitivity can be optimized in some areas of the material with the use of focused transducers.

4. Angle Beam

This again has just one element and is used alongside a wedge. This is done to bring either longitudinal wave or shear wave to the test material. The wedge (could be integral or removable) introduces sound into the object from an angle.

These devices are used to test the integrity of a weld. This is because, for weld inspection, it is required that sound waves be aimed at a certain angle. Some other common applications of this device are crack sizing and flaw detection.

The wedge used here typically comes in several sizes that are used to meet particular needs.

5. Delay Line

These also have just one element and are used alongside a delay line. With this transducer, the time between generating sound waves and when the reflected wave arrives is delayed. This is done to help improve the resolution near-surface.

This type of transducer is applied in the following ways:

  • For high temperature
  • Inspection of parts that do not have enough contact areas
  • Detecting flaws in thin materials

Ultrasonic Transducers Pros and Cons

Just as with everything, ultrasonic transducers also have their benefits and drawbacks.

Pros

They can be used to measure any material type; in addition to that, they can sense substances of any kind. They aren’t affected by environmental factors such as temperature, dust, or water. This means that regardless of the environmental situation, they will work properly.

Cons

They are sensitive to both immediate and high-temperature variation. These conversions are usually unexpected and can affect the transducer’s detection ability. Also, they tend to face some challenges when identifying small targets’ (too soft or thin) reflections.

Fortunately, studies and research are being done to tackle these problems.

Ultrasonic Transducer – Components

These devices have 3 main components:

1. Piezoelectric Crystal

This is the device’s center and the system’s “active ingredient”. The transducer’s piezoelectric crystal tolerates compression as well as rarefactions to ensure electrical energy is transformed into either contrariwise or ultrasonic energy.

Another part that is used to create electrical pulse so that they can be sent to the device is known as the fault detector.

2. Wear-Plate

Wear-plates are put in the device as a support for the device’s piezoelectric crystal. It usually protects the device from environmental problems such as corrosion, tear, and wear. Generally, wear-plates are used as the acoustic converter that stands between the device’s piezoelectric crystal and a wedge, delay line, or water.

3. The Backing

This is equally very important. The backing is a quite dense substance that has the sole purpose of absorbing the energy emitting out of the crystal’s back so that the vibrations can be monitored.

You can watch this video: https://www.youtube.com/ to get a better understanding of the workings of ultrasonic technology.

Conclusion

Ultrasonic transducers are devices that use sound waves to calculate the distance to a particular target. Intervals are calculated by sound waves being sent out on a certain frequency. These devices come in several types such as angle beam, delay line, immersion, dual element, and contact transducers; all of which have been discussed in this article. The basic components of this device as well as its pros and cons were also discussed in this article.

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