Ring Hoop Tension Test (RHTT): A Test for Transverse Tensile Properties of Tubular Materials

Abstract Tube hydroforming has been receiving increasing attention, particularly for making automotive components. In this process, tubular metal pats are formed within a die cavity by forcing pressurized fluid inside so that the part expands into its final shape in a die. Process control requires an improved knowledge of mechanical properties in the transverse direction of tubular products. Several laboratory tests have been used to evaluate tube properties. One test method that has been used for zirconium alloy cladding tubes in the nuclear industry is the ring test, in which an expansion force is applied from inside the ring by separating two die inserts. In the present work, this test method is adapted to determine the hoop stress-strain curve of tubular materials. The new protocol allows measurement of the tensile properties without altering those properties in specimen preparation, which occurs using the conventional flattened strip tensile test. This paper presents the new test and data analysis procedure, along with typical data for a commercial steel hydroforming tube.