Determination of the flow stress of magnesium AZ31-O sheet at elevated temperatures using the hydraulic bulge test

Elevated temperature hydraulic bulge tests for Mg AZ31-O alloy sheets were conducted using a submerged tool, designed to minimize the temperature variation in the sheet. Experiments were conducted between room temperature and 225 °C, at various approximate true strain rates. Bulge profiles at different bulge heights were measured using a CMM and the best radius values were calculated through least-square fit using several measured points. Residual plots were made to demonstrate the amount of deviation from a sphere with increasing bulge height. Measured and calculated bulge radius and thickness values were compared with the available analytical models. Amount of error that occurs in flow stress calculation by deploying the well-known membrane theory was investigated.