A special notched tensile specimen to determine the flow stress-strain curve of hardening materials without applying the Bridgman correction. (15th June 2017)

• Record Type: Journal Article
• Authors: Tu, Shengwen; Ren, Xiaobo; Nyhus, Bård; Akselsen, Odd Magne; He, Jianying; Zhang, Zhiliang
• Is Part Of: Engineering fracture mechanics. Volume 179(2017)
• Page Start: 225
• Page End: 239
• Publication Date: 2017-06-15
• Subjects: Flow stress-stain curve -- Notched tensile specimen -- True stress-strain curve -- Weldment -- Bridgman correction; Fracture mechanics -- Periodicals; Rupture, Mécanique de la -- Périodiques; Fracture mechanics; Periodicals; 620.112605
• DOI: 10.1016/j.engfracmech.2017.04.039
• Languages: English
• ISSNs: 0013-7944

Abstract

Highlights: A special geometry of cylindrical notched tensile specimen is proposed for measurement of materials' flow stress-strain curve. The proposed method can obtain material's flow stress-strain curve directly without performing the well-known Bridgman correction. The proposed method can be applied to obtain the flow stress-strain curve of each individual material zone of a weldment. Abstract: 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 Lüders plateau in the initial yield region.