Ultrasonic testing (or USI, ultrasonic inspection) is one of the best ways to ensure that aluminum plate and other materials meet certain thresholds of material integrity. It exposes hidden flaws and imperfections that would have otherwise gone undetected.


What is ultrasonic testing?

Ultrasonic inspection is a form of non-destructive testing that propagates high frequency sound energy into the subject material.  The frequency of the sound waves typically falls in a range between 0.1 MHz all the way to 50 MHz.

An example of how the technology is used in an industrial setting is the determination of the dimensions of the material being tested.  This can be critical information, such as in the monitoring of pipework corrosion.

Ultrasonic testing is most frequently associated with stainless steel, aluminum, and other metals.  Forgings, castings, wrought and cast plate, extrusions and bar stock can all be subject to USI.  It is sometimes used with other materials, including concrete, wood, plastic and composites.  It should be mentioned that these other materials offer poor resolution under ultrasonic inspection.

A typical UT inspection system consists of several functional units: a pulser/receiver, transducer, and display devices.  The transducer will directly contact the material that is being tested.  With most forms of ultrasonic testing the transducer must be connected to the material via a couplant, or it must be immersed in water.  The pulser produces high voltage electrical energy, which is generated into high frequency ultrasonic energy by the transducer and conducted into the subject material.

There are two options for receiving the ultrasound waveform.  The first form is known as reflection, in which the transducer does both the sending and receiving of the pulsed waves.  Reflected ultrasound works on the principle that any imperfection within the material will be signaled back to the device in the wave.  Attenuation ultrasound works by having a transmitter send the ultrasound through one side of the material, to a separate receiver on the other side.  Imperfections will lower the amount of sound that gets transmitted.

The use of the couplant or immersion in water helps to bolster the accuracy of the process, serving as an efficient conductor between transducer and test piece.


How is ultrasonic testing used with aluminum plate?

Traditionally, there have been two options for ultrasonic testing aluminum plate.  The first, as mentioned above, is contact ultrasound, in which a couplant is used to increase the efficiency of the testing signal.

It works on the principle that sound waves are directional through a material.  Once they encounter the boundary of a crack, void or inclusion within the plate, this alters the sound wave, which is reflected in the amplitude of the wave-reading device in the testing machine.  The travel time of the ultrasonic signal is directly related to the distance the signal has travelled in the material; this way the location, size, and orientation of different imperfections can be detected.

As noted above, contact ultrasonic testing works on the principle that the couplant helps to provide better contact between the signal transmitter and the test material, boosting the efficiency. The couplant material is generally some form of oil or gel that basically acts like a seal between the two.

Immersion ultrasound systems are precision machines, and the most recent versions offer many automated functions for increased accuracy.  They include sizable tanks into which the material to be tested is submerged.  The liquid environment serves a very similar function to the couplant in contact ultrasonic testing.


What are the most common specifications for ultrasonic testing?

Since its advent in the 1940’s, ultrasonic testing has advanced to include several different techniques, and to ensure quality across the many different options, several competing standards have arisen.  AMS STD 2154 and ASTM B294 are a couple of the more popular specifications, which lay out uniform methods for the ultrasonic inspection of wrought metals and alloys.

In the aerospace industry, many of the manufacturers have their own USI procedures specific to the airframes they produce.

The International Organization for Standardization (ISO) offers several specifications that cover many of the use case scenarios for non-destructive ultrasonic testing. For example, ISO 10863 was formulated to standardize the non-destructive testing of welds, via ultrasonic testing, and specifically addresses the use of time-of-flight diffraction technique. ISO 5577 lays out the vocabulary associated with ultrasonic testing.


What industries are likely to rely upon ultrasonic testing?

Anytime performance and structural integrity are critical requirements, materials testing is a necessity.  Industries that typically rely on ultrasonic testing include aerospace, defense, automotive, construction, metallurgy, manufacturing, high-speed rail and more.


Your Trusted Aluminum Plate Supplier

When it comes to aluminum plate products, manufacturers want the best, most reliable materials. This is where ultrasonic testing comes into play.  Whether having material ordered from the production mill to the correct USI specification or processing our current material inventory using partnerships in the testing industry, Preferred Alloys can support your requirements.  At Preferred Alloys, we’ve been a leading supplier of aluminum and stainless steel products in the Midwest and beyond for over four decades.

Contact us today to speak with one of our knowledgeable and friendly sales professionals.