Published on 10-Jan-2024

What are the Different Types of Ultrasonic Transducers?

What are the Different Types of Ultrasonic Transducers?

Table of Content


Introduction

Ultrasonic transducers play a pivotal role in Non-destructive Testing by utilizing high-frequency sound waves to assess critical parameters.

These indispensable devices find applications across various industries, including flaw detection, thickness measurement, and weld inspection.

Given the diversity of Ultrasonic Testing transducers available, selecting the right one for a specific application can be a daunting task. 

Types of Ultrasonic Transducers

Let's delve into five common types of industrial ultrasonic transducers for industrial purposes.

Dual Element Transducers

1. Dual Element Transducers - Enhancing Precision with Dual Element Transducers

The dual-element transducer, as the name suggests, consists of two crystal elements enclosed within a single housing, with an acoustic barrier separating them.

One of these elements generates sound waves, while the other acts as a receiver.

The innovative design of dual-element transducers leads to a V-shaped sound path within the test material, as the two elements are angled towards each other.

This arrangement results in a pseudo-focus effect, significantly enhancing resolution in the focal zone.

When examining components with rough back wall surfaces, the pseudo-focus effect's increased sensitivity proves to be particularly useful.

As a result, these transducers have become the industry standard for measuring remaining wall thickness in Corrosion-related applications.

However, their utility extends beyond this, encompassing:

  • Weld overlay and cladding bond/disband inspection
  • Detection of porosity, inclusions, cracks, and laminations in castings and forgings
  • Crack detection in bolts and other cylindrical objects
  • High-temperature applications

2. Contact Transducers -Direct Contact Inspections Made Easy with Contact Transducers

As the name suggests, contact transducers are tailored for direct-contact inspections.

These single-element transducers boast a wear-resistant surface optimized for contact with most metals, rendering them robust and durable for use in rugged industrial environments.

Contact transducers come in various styles and configurations, including fingertip variations designed for challenging-to-access areas.

Contact Transducers

These versatile devices find applications in:

  • Straight beam flaw detection
  • Thickness measurement
  • Detecting and sizing delaminations
  • Inspecting plates, billets, bars, and other metallic and non-metallic components
  • Velocity measurements

3. Angle Beam Transducers - Testing Weld Integrity with Angle Beam Transducers

Angle beam transducers are single-element types of transducers that work with a wedge to send either a refracted shear wave or a longitudinal wave into the test piece.

The wedge, whether removable or integral, introduces sound at an angle into the part being inspected.

Inspectors frequently employ angle beam transducers in Weld Integrity Testing, as this particular inspection requires directing sound waves at an angle.

Wedges are available in a multitude of sizes to cater to specific requirements. 

Some offer shorter approach distances, while others are tailored for high-temperature applications.

Select wedges can even be customized to create nonstandard refracted angles and contours.

Key Applications include: 

4. Delay Line Transducers - Enhancing Near-Surface Resolution with Delay Line Transducers

Delay line transducers, as the name suggests, are single-element transducers designed to work in conjunction with a replaceable delay line.

These transducers introduce a time delay between the generation of the sound wave and the arrival of the reflected waves, thereby improving near-surface resolution.

Their higher frequency makes them ideal for inspecting or measuring thin materials and locating small flaws while using the direct contact method.

With their replaceable delay line, these transducers prove versatile for a wide range of industrial applications.

Some common uses include:

  • Precision thickness measurement
  • Flaw Detection in thin materials
  • Inspecting parts with limited contact areas
  • High-temperature applications

5. Immersion Transducers - Diving into Water-Based Inspections with Immersion Transducers

Immersion transducers represent a unique category of single-element transducers designed to operate underwater.

Rather than making direct contact with the test piece, these transducers use a column or bath of water to couple sound energy into the material.

The immersion technique enables uniform and rapid coupling, facilitating quick scanning of parts.

Inspectors can opt for focused transducers to enhance sensitivity and performance in specific areas of a component.

Immersion transducers are often used for in-line or in-process tests on moving parts, automated scanning, and getting the best sound coupling into sharp corners, grooves, or channels in test pieces with complicated shapes.

Key applications include:

  • In-line thickness measurement
  • High-speed Flaw Detection
  • Time-of-flight and amplitude-based imaging
  • Material analysis and velocity measurements

Understanding Various Types of Transducers

Understanding the nuances of various ultrasonic transducer types is essential for making informed decisions in industrial applications.

Each type serves a unique purpose and excels in specific scenarios.

By choosing the right type of ultrasonic transducer for your requirements, you can enhance the accuracy and efficiency of your Non-destructive Testing processes, ultimately contributing to safer and more reliable industrial operations.

Conclusion

These are versatile devices with a wide range of applications across industries.

From medical imaging to Aerospace, they continue to shape the way we work and live.

As technology advances, we can expect even more exciting developments in the world of transducers.

They are commonly used due to their ability to produce and detect high-frequency sound waves that are beyond the range of human hearing.

FAQs

1. Where are Ultrasonic transducers used? 

A: Ultrasonic transducers have a wide range of applications, including but not limited to Ultrasonic Cleaning, Distance Measurement, Medical Imaging, Non-destructive Testing (NDT), Underwater Sonar, Animal Repellents, Level Measurement, and Material Thickness Gauging, etc.


Q: What is the frequency of the ultrasonic transducer?

A: The frequency of ultrasonic transducers can vary widely depending on their intended application.

Typical frequencies range from a few kilohertz (kHz) to several megahertz (MHz). For example, medical ultrasound transducers often operate in the range of 1–15 MHz, while industrial applications might use lower frequencies in the kHz range for thicker materials.

 

Q: What is the size of a transducer?

A: The size of an ultrasonic transducer can also vary significantly based on its purpose and operating frequency.

Medical transducers are typically small and handheld, while industrial transducers can be larger and designed for specific applications.

Sizes can range from a few millimeters to several centimeters or even larger, depending on the design and requirements.


Q: Are there any emerging technologies in Ultrasonic Transducers?

A: Some emerging technologies in the various types of transducers.

  •  Flexible and Wearable Transducers: Research into flexible and wearable ultrasonic transducers for medical and health monitoring applications.
  • High-Frequency Transducers: Development of transducers operating at even higher frequencies for improved resolution in medical imaging and materials testing.
  • MEMS-based Transducers: Integration of microelectromechanical systems technology to create smaller and more precise ultrasonic transducers.
  • Multi-Modal Imaging: Combining ultrasound with other imaging modalities like photoacoustic imaging or elastography for enhanced diagnostics.

References:

1. Cygnus Instruments

2. Baker Hughes



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