Development of Ultrasonic Standard Reference Blocks of Aerospace Quality

Ultrasonic standard reference blocks are extensively used in calibration and performance evaluation of Ultrasonic flaw detectors. They are also used in inspection of metallic raw materials like forgings, castings and rolled sections apart from machined components for any flaws like cracks, inclusions etc. These reference blocks consist of precisely drilled flat bottom holes (FBH) to act as intentional flaws and they are made from the same material that is to be inspected to get the same acoustic response. The typical test materials are Titanium alloys, Copper alloys, Aluminium alloys and Steels. Ultrasonic response tests are carried out for studying the intensity of the returned echo from the flat bottom, over different metal travel distances. Reference blocks with flat bottom of dia from 2 mm down to 0.5 mm are used mainly in aerospace applications. This paper deals with the manufacturing and inspection techniques employed in the indigenous development of Titanium Alloy reference blocks of 1.2 mm FBH.