Bar or tube production of any type of metal alloy, steel, aluminium brass and also plastics often requires non destructive testing for quality certification.
Ultrasonic bar testing and tube testing is used to inspect the material for the full body and is performed in-line or off-line during or after production.
Depending on the production circumstances and testing speed the bar will be rotated for inspection or the sensors need to rotate around the material when it is not posible to rotate the bar or tube.
For most off- line inspections the bar or tube will be rotated with a number of ultrasonic transducers positioned for proper defect detection such a cracks, inclusions, thickness variations (tube wal thickness) etcetera.
For in-line testing it is often not possible. In this case there are various ways for testing. Phased array is used more often nowadays but multi element around the products is also an effective and high speed method. The highest reliability in combination with testing speed is yet achieved with rotating transducers (https://youtu.be/ukOGpjtQAy8) because these can be sharply focussed for accurate defect detection.