A special notched tensile specimen to determine the flow stress-strain curve of hardening materials without applying the Bridgman correction

摘要

Structural integrity assessment of weldments requires the input of flow stress-strain curve of each individual material zone. To cope with these challenges, a cylindrical cross weld tensile specimen with a notch located either in the weld metal, base metal or possibly heat affected zone has been previously developed by the authors to determine the true stress strain curve for the material zone of interest. The disadvantage of this notched tensile testing method as well as the standard tensile testing method using a smooth specimen, is that the well-known Bridgman correction still has to be applied in order to obtain material's equivalent or flow stress-strain curves. In this study, tensile specimens with various notch geometries have been scrutinized and a 'magic' specimen with a special notch geometry has been identified. By using this special notched tensile specimen, material's flow stress-strain curve can be directly calculated from the recorded load versus diameter reduction curve and no Bridgman correction is needed. The method is very accurate for power-law hardening materials and becomes less accurate for materials with significant Luders plateau in the initial yield region. (C) 2017 Elsevier Ltd. All rights reserved.