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​​Ultrasonic Contact Transducer: Advantages and Application

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Ever had to wonder what benefits an ultrasonic contact transducer has over other transducers? 

While many non-destructive testing tools offer several benefits, ultrasonic transducers seem to pack a lot of these benefits. Ultimately, an ultrasonic contact transducer offers so many benefits that has made it the preferred tool for assessing the quality of materials and for detecting flaws. However, its popularity does not translate to a full understanding of its application and use cases even among quality inspectors.

In this post, you’ll get all the information about ultrasonic contact transducers including its advantages and applications for several unique conditions. So, if you are ready to know more, then let’s dive in.


What is an Ultrasonic Contact Transducer?

To begin with, ultrasonic contact transducers, like all transducers, detect high frequency sound signals which often fall within the range of 1 -10 MHz. 

Also, ultrasonic contact transducers are unlike multi-element transducers like phased array transducers where more than one element is used for projecting and receiving signals. They typically use one element both for generating and receiving signals. Although, certain conditions might require other setups including the use of dual elements. 

Generally, contact transducers release longitudinal waves to make direct contact with the test sample. Nevertheless, due to the difference in surface textures of various test samples, ultrasonic contact transducers often come manufactured with sturdy materials. The essence of this sturdy material is to overcome the tear and wear from rough surfaces.  Yet the acoustic impedance of contact transducer is very high to take care of applications involving metallic materials.


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What are Types of Ultrasonic Contact Transducers?


Typically contact transducers have various applications and as such have different setups that allow them function optimally for these peculiar use cases. The different types of contact ultrasonic transducers are highlighted below.


Straight Beam (single element) – This type of contact transducer uses the classic setup of a single element for both sound projection and signal reception. Nonetheless, it functions effectively for assessing the quality of components with regular shapes and with smooth faces. For instance, flat samples or curved surfaces with the need for flaw detection. This contact transducer can be effective for assessing thick surfaces with the use of couplants like gels or oils. 


Straight beam (dual element) – Unlike the single element type the dual element straight beam is effective for scanning thin surfaces and often requires manual operations. However, they can also detect flaws and parallel backwalls when necessary just like the single element type. Also, when the conditions are right, including reduced noise and high resolution of the near surface, this transducer can both receive and transmit mechanical and electrical signals with its elements parted by a crosstalk block. Still, you’ll need a couplant like a gel or oil when in contact with both rough and curved surfaces. 


Angle beam – This type is often effective for assessing the quality of welds and other inclined parts for flaws and other defects. Sometimes, it can also be efficient for high-level automation or mechanized testing by employing refraction to project both longitudinal and shear waves which are different from the shear waves generated by most other standard transducers. Again, this type of transducers needs couplants like gels and oils for more effective. 


Types of Ultrasonic Contact Transducer



What are the Features and Advantages of Ultrasonic Contact Transducers?


Ultrasonic contact transducers have features that make it both similar and different to other types of transducers. 

Some of these features include its frequency range, which, like most ultrasonic transducers, fall within the range of 1 – 10 MHz even though there are special transducers that can detect lower or higher frequencies than this range. Also, it features a single element for both projecting and receiving sound signals. Additionally, the nominal element diameters fall between 13 – 39 mm. Still, it uses straight beams to detect flaws and for thickness gauging and can accurately test materials of temperature as high as 50°C. 

These features contribute to the uniqueness and advantages of ultrasonic contact transducers. These advantages include

  • Sturdy and tough material that can withstand the impact of rough surfaces and harsh usages which makes it more durable than most of the other transducers.
  • A wide array of material testing applications which increases its usage preferences and versatility including testing forgings, billets, and extrusions. 
  • It matches most metals with its close acoustic impedance



What does an Ultrasonic Contact Transducer do?


An ultrasonic contact transducer is a single element longitudinal wave transducer intended for use in direct contact with a test piece. At a basic level a contact transducer is used to convert electrical signals into ultrasound and send high-frequency sound into a test piece and then receive the resonates. This signal is transferred to a flaw detector that converts the signals into data that an inspector uses to help detect flaws. 

However, at a detailed level it converts a pulse of electrical energy from the flaw detector into mechanical energy in the form of sound waves that travel through the part being inspected. The sound waves returning from the part are converted by the transducer into a pulse of electrical energy that can be processed and displayed by the flaw detector. 

The transducer essentially acts like a speaker and microphone, generating and receiving pulses of sound waves at frequencies much higher than the range of human hearing. 



What are the Applications of Ultrasonic Contact Transducers?


The ultrasonic contact transducer is by far the most widely used of all types of transducers simply because most flaw detection requires contact with the sample material. 

Also, these applications hinge on the advantages that Contact Ultrasonic Transducers deliver for non-destructive testing and material characterization purposes. These applications include


  • Thickness gauging and straight beam flaw detection – Material thickness gauging is often very important for manufacturers especially in the automotive and aviation industries where materials of specific thickness are designed to withstand certain stresses and force impacts. Also, the level of corrosion of metallic materials is another challenge these manufacturers use Ultrasonic Contact Transducers to overcome. 


  • Detection and sizing of delamination – For materials that are composed of layers, the most challenging failure occurring for these materials is delamination often caused by internal cracks. Contact Transducers are by far the most accurate non-destructive device for identifying and sizing this delamination. 


  • Inspection of ferrous and non-ferrous materials – Different metals including billets, forgings, bars, castings, extrusions plates, and various other metals are best inspected for defects using Ultrasonic Contact Transducers.  Ultrasonic Contact transducers are also accurate for identifying flaws in non-metallic components used in the manufacturing industries. 


Application of Ultrasonic Contact Transducer



How to Choose an Ultrasonic Contact Transducer?


Deciding to use a transducer can be dependent on predictable criteria including the type of environment and material under examination. Nevertheless, when choosing an ultrasonic contact transducer, you might need to fulfill certain necessary conditions and criteria to choose the right one. 

Firstly, you need to consider the level of accuracy required for your testing situation. The reason is because every quality assessment operation has their individual level of accuracy that is required. These accuracy requirements are different for individual cases. Hence, it is important that you identify if the accuracy of ultrasonic contact transducers is not higher than the accuracy you desire as it often has a higher cost implication as the accuracy increases. 

Also, you may have to consider the material under examination including its surface texture, curvature, and geometry. You can effectively carry out testing with a high degree of accuracy for components with awkward or irregular geometry which might be difficult for other transducer types. 

Lastly you need to find a supplier with an extensive track record of successful delivery of quality ultrasonic contact transducer. You might have to peruse a significant number of customer reviews to find a suitable one. Also, ensure that the supplier has competitive pricing while upholding international standards of quality. 


how to choose Ultrasonic Contact Transducer




In conclusion, understanding that ultrasonic contact transducers are similar to other ultrasonic testing devices in that they use ultrasonic signals to identify defects in sample materials. Also, their uniqueness in application makes them a widely acceptable inspection tool within the non-destructive testing and inspection industry. 

Still, choosing a suitable ultrasonic contact transducer may require considering factors like the level of accuracy required. the type of material under examination, and a reliable supplier with a verifiable track record of successful delivery. 

Ultimately, knowing how and when to employ ultrasonic contact Transducers is as important as knowing when to employ them.

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