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Influence of Shear Lip Symmetry on the Fracture Behavior of Charpy Specimens

Published

Author(s)

Enrico Lucon

Abstract

An investigation was conducted at the National Institute of Standards and Technology (NIST) on the influence of shear lip symmetry on the fracture behavior (absorbed energy and data scatter) of Charpy specimens at different energy levels, corresponding to NIST low-energy, high-energy, and super-high-energy certified specimens. Whenever both shear lips are on the same tested specimen half (symmetrical fracture), absorbed energy tends to be lower than when each specimen half includes one shear lip (asymmetrical fracture). Fracture type does not have a significant effect on impact toughness or variability at low- or high-energy level, but its influence becomes significant around 200 J and above. Specifically, super-high-energy specimen lots do not fulfill the NIST requirement (sample size  5.0) when both fracture types are combined, while they may become acceptable if only symmetrical or asymmetrical fractures are considered. This tendency is particularly clear for the 9310 (3Ni) steel, which is presently under consideration for the reinstatement of super-high-energy specimens in the NIST catalog. We have found that the most effective method for preventing the formation of shear lips, and therefore avoiding this type of bimodal behavior, is to side-groove the Charpy specimens for a total thickness reduction of 10 %.
Citation
ASTM Journal of Testing and Evaluation
Volume
47
Issue
2

Keywords

Asymmetrical fracture, indirect verification Charpy specimens, shear lips, sample size, side-grooving, symmetrical fracture.

Citation

Lucon, E. (2019), Influence of Shear Lip Symmetry on the Fracture Behavior of Charpy Specimens, ASTM Journal of Testing and Evaluation, [online], https://doi.org/10.1520/JTE20180403, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=925805 (Accessed April 20, 2024)
Created January 31, 2019, Updated April 11, 2023