This International Standard specifies a method for a ring-expanding test on tubes, that is used to reveal defects both on the surfaces and within the tube wall by expanding the test piece using a conical mandrel until fracture occurs. It may be also used to assess the ability of tubes to undergo plastic deformation. The ring-expanding test is applicable to tubes having an outside diameter from 18 mm up to and including 150 mm and a wall thickness from 2 mm up to and including 16 mm.