Evaluation of ultimate tensile strength using Miniature Disk Bend Test

Since inception of Miniature Disk Bend Test (MDBT) technique, UTS correlations have been an open issue. Correlations based on Pmax of load–displacement curve are also in disagreement as the point corresponding to Pmax does not represent a necking situation as in case of UTS, in a uniaxial tensile test. In present work, an attempt has been made for locating necking zone, which appears prior to Pmax, through experiments and FEM analyses. Experimental results on disk specimens from 20MnMoNi55, CrMoV ferritic steel and SS304LN materials along with FEM analyses found that load corresponding to 0.48mm displacement is to be very close to the necking zone, and gives best fit for a UTS correlation. (a) Plots of thickness of disk at various radial locations for different punch travel distances for 20MnMoNi55 and (b) derivative of minimum thickness on the disk with punch travel. [Display omitted] •Correlations for UTS in a SPT have been an open issue since the development of this technique.•The point Pmax in SPT curve does not correspond to a necking as in P-δ curve in tensile test.•In this work attempt has been made to locate necking in SPT curve using experiments and FEM.•The data corresponding to 0.48mm displacement is found to be very close to the necking zone.•It is found that correlation for UTS is best suited for data corresponding to the necking zone. Correlations for evaluation of Ultimate Tensile Strength (UTS) using Miniature Disk Bend Test (MDBT) or Small Punch Test (SPT) has been an open issue since the development of the techniques. The larger plastic strains, in tri-axial state of stress during SPT, make the translation to the equivalent uniaxial parameter less certain. Correlations based on Pmax of load–displacement curve are also in disagreement as the point corresponding to Pmax does not represent a necking situation as in case of UTS, in a uniaxial tensile test. In present work, an attempt has been made for locating necking zone, which appears prior to Pmax, through experiments and FEM analyses. Experimental results on disk specimens from 20MnMoNi55, CrMoV ferritic steel and SS304LN materials along with FEM analyses found that load corresponding to 0.48mm displacement is to be very close to the necking zone, and gives best fit for a UTS correlation.