The hydraulic bulge test to ISO 16808 is a test method used in materials testing for the determination of sheet metal forming properties.
In a bulge test biaxial stress-strain curves are determined on sheet metals using a hydraulic cupping test. A metal blank (specimen) is fully clamped between the matrix and the blank holder. Under the specimen there is a chamber with oil. The drawing die pushes the oil up. The continuously increasing oil pressure leads to a curvature in the specimen. The test is run until a crack occurs.
Following the bulge test, the flow curve can be determined. For this the oil pressure, the evolution of the sheet metal thickness during the test and the optical measurement and assessment of the curvature in the sheet metal are evaluated.
The test is similar to the FLC test with Nakajima die. The cupping procedure however, takes place without friction.