The Limiting Dome Height Test for Assessing the Formability of Sheet Steel

The Limiting Dome Height (LDH) test has attracted much interest as a simulative tool for predicting press performance of materials. However, problems of test reproducibility have been observed. An experimental evaluation has been performed to determine the possible source or sources of these problems. The evaluation was performed using both uncoated and coated mild steels. A small tooling temperature rise and minimal punch - die misalignment had little effect on the LDH_O value and on reproducibility. Increased clamping forces above a minimum threshold value improved reproducibility but did not significantly change the LDH_O value. A low viscosity oil for cleaning and lubricating test samples was found to give the most satisfactory results. A correlation was found between LDH_O and both the strain-hardening exponent and the total elongation obtained from uniaxial tensile tests. The lack of LDH test reproducibility remains unexplained. Normalization using a standard material to address the test reproducibility was evaluated. Use of the test as a quality control tool will require a rigorous assessment of the capability of the test to reflect material variation in a reproducible manner.