What Is Ultrasonic Testing Used For?

What Is Ultrasonic Testing Used For? 

What is ultrasonic testing used for? Ultrasonic testing is a versatile method of Non-Destructive testing that can be applied to most materials. It doesn’t matter whether they are metallic or non-metallic. 

Ultrasonic non-destructive testing is a way of characterising thickness and internal structure of a test piece. This is done with the use of high frequency sound waves. These frequencies, or pitch, used for are many times higher than the limit of human hearing. They are most commonly found in a range from 500 KHz to 20 MHz. 

Ultrasonic testing is just one method of Non-Destructive Testing that Format NDT use. Here, we’ll explain what it is used for and how it works.  

How does ultrasonic testing work? 

Ultrasonic testing requires the analysing of sound reflections to measure the thickness of a test piece., or to find hidden flaws or surface cracks.  

Sound waves that are high frequency are very directional. They can travel through a material such as a piece of steel or plastic, until they come across another medium, such as air. At this point they will reflect back to their source. This is how it is possible to detect faults.  

What are the types of material ultrasonic testing works on?  

Within industry, this form of testing is used on:  

  • Metals 
  • Plastics 
  • Composites 
  • Ceramics 

It is also used within bio medics, for diagnostic imaging and medical research purposes.  

The advantages of ultrasonic testing 

The advantages of ultrasonic testing are as follows: 

  • Ultrasonic testing is one hundred percent non-destructive.  
  • The piece that is undergoing non-destructive testing need not be either cut, sectioned, have undergo any exposure to damaging chemicals.  
  • There only needs to be access to one side of the material.  
  • There are no health hazards associated with this type of testing, particularly in the bio medic field.
  • Results are reliable and repeatable. 

Are there any disadvantages to ultrasonic testing? 

There are relatively few disadvantages to ultrasonic testing:  

  • This type of testing should only be performed by professional and trained operators who can set up tests and know how to properly interpret the results.  
  • Inspection of more complex materials may be more challenging and require multiple setups. This is dependent on the type of material being examined and it’s thickness.   
  • Ultrasonic thickness gauges can sometimes be slightly more costly than other types of measurement device.  

Ultrasonic thickness gauges explained 

This is a type of gauge that will generate sound pulses in a test piece. It will accurately measure the time interval before echoes are received.  

The test material will have been programmed with the speed of sound. The gauge will simply use the sound velocity information and the time interval, in order to calculate the thickness. The formula would be thus:  

  • distance = velocity x time 

Commercial ultrasonic gauges can achieve high accuracy in most common materials used in engineering.  

What affects accuracy? 

  • How uniform the sound velocity is in the material being tested.  
  • How much sound scattering or absorption there is 
  • The condition of the surface 
  • The accuracy with which the instrument has been calibrated for what it will be used for 

Ultrasonic gauges can be used to detect the measurement of any remaining wall thickness in corroded pipes and tanks.  

This measurement can be made fast and effectively and there is no need to have any access to the inside of the component, or to have any tanks emptied.  

They can also be used to measuring the thickness of: 

  • Moulded plastic bottles  
  • Turbine blades or any other type of precision machined parts 
  • Small diameter medical tubing 
  • Tyres  
  • Conveyor belts 

Ultrasonic flaw detectors explained 

When sound waves travel through a material, they will reflect in predictable ways off flaws such as cracks and voids.  

An ultrasonic flaw detector is an instrument that gives off and processes ultrasonic signals that can be used by a trained professional to find flaws in a test piece, that might otherwise be hidden.  

The tester will find the reflection pattern for a ‘good’ part then look for changes in the reflection to indicate any flaws.  

They can be used to detect: 

  • Cracks 
  • Voids  
  • Disbands  
  • Inclusions 

In fact, they can be used to find any issues that might affect structural integrity  

The flaw size that needs to be detected will depend on: 

  • The material being tested 
  • The flaw under consideration 

Ultrasonic flaw detectors are used in safety and quality related applications that involve: 

  • Structural welds 
  • Steel beams 
  • Forgings 
  • Pipelines 
  • Tanks 
  • Aircraft engines and frames 
  • Car frames 
  • Power turbines and other heavy plant machinery 

Ultrasonic transducers explained 

An ultrasonic transducer is a device that turns one form of energy into another. It will convert electrical energy into mechanical vibrations, and also sound waves into electrical energy.  

They are often small, hand held pieces of equipment, that come in a wide variety of frequencies so that they can accommodate the needs of the specific tests they are being used for.  

Are other types of instruments for ultrasonic testing available? 

Ultrasonic imaging systems can also be used to generate highly detailed pictures that are similar to x rays. These will map the internal structure of a part using sound waves.  

Phased array technology, which was originally developed for medical diagnostic imaging is used in some industrial situations in order to create cross-sectional pictures. 

Within the aerospace industry and also in metalworks, large scanning systems are used to check for hidden flaws in both the raw materials and also in the finished parts.  

Format NDT For Ultrasonic Testing 

Format NDT work with a team of highly trained professionals to provide all forms of non-destructive testing across a wide range of industries.  

If you would like to find out more about the services we offer, or how we can help you specifically with ultrasonic testing, then contact us today on 01744 816 225