Open source ultrasound non-destructive testing (NDT)

Nondestructive testing is a method of finding defects in an object without harming the object. Often finding these defects is a very important task. In the aircraft industry, NDT is used to look for internal changes or signs of wear on airplanes. Discovering defects will increase the safety of the passengers. The railroad industry also uses nondestructive testing to examine railway rails for signs of damage. Internally cracked rails could fracture and derail a train carrying wheat, coal, or even people. If an airplane or a rail had to be cut into pieces to be examined, it would destroy their usefulness. With NDT, defects may be found before they become dangerous.

How is ultrasound used in NDT?

Basically, ultrasonic waves are emitted from a transducer into an object and the returning waves are analyzed. If an impurity or a crack is present, the sound will bounce off of them and be seen in the returned signal.

One type of ultrasonic testing places the transducer in contact with the test object. If the transducer is placed flat on a surface to locate defects, the waves will go straight into the material, bounce off a flat back wall and return straight to the transducer. The animation below, developed by NDTA, Wellington, New Zealand, illustrates that sound waves propagate into a object being tested and reflected waves return from discontinuities along the sonic path. Some of the energy will be absorbed by the material, but some of it will return to the transducer.

Ultrasonic measurements can be used to determine the thickness of materials and determine the location of a discontinuity within a part or structure by accurately measuring the time required for a ultrasonic pulse to travel through the material and reflect from the backsurface or the discontinuity.

Open source in NDT

I haven't seen much open-hardware for ultrasound non-destructive testing. Even if many of the tests in this project were run in B-Mode for 2D imaging, nothing prevents one from using this hardware to do A-mode for NDT.

• @todo Further tests for NDT to come.