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ASTM E08.07.09 Analytical Round-Robin on the Use of DC Electrical Potential Difference for the Measurement of Crack Size in Ductile Fracture Testing

Published

Author(s)

Enrico Lucon

Abstract

The Direct Current Electrical Potential Difference, DCEPD, technique has been used for many years in fatigue and fracture testing for monitoring crack propagation in metallic materials. The principle of DCEPD methods is that, when a constant current flows through a cracked specimen, the voltage change measured across the crack plane can be analytically and/or empirically related to the change in crack size. In fatigue testing, where stresses are kept within the linear elastic boundaries, crack propagation is the sole source of potential difference. In fracture testing, additional contributions from specimen dimension changes and crack tip plastic deformation (blunting) have to be accounted for and distinguished from the DCEPD increase caused by crack growth. The ASTM E08.07.09 Task Group, formed in 2013 and chaired by the author, has been developing an annex for ASTM E1820 which focuses on the use of DCEPD measurements for the prediction of crack size and crack extension in ductile fracture toughness tests. This paper presents the analysis of an analytical round-robin, in which several participants analyzed existing fracture toughness data sets using two different approaches, based on the analysis of the displacement vs. DCEPD and force vs. DCEPD, respectively. The comparison between these two approaches, and the implication for the E1820 annex being developed, are the focus of this paper.
Citation
Materials Performance and Characterization

Keywords

DCEPD, potential difference, fracture toughness, J-R curve, crack size, ductile crack extension

Citation

Lucon, E. (2018), ASTM E08.07.09 Analytical Round-Robin on the Use of DC Electrical Potential Difference for the Measurement of Crack Size in Ductile Fracture Testing, Materials Performance and Characterization, [online], https://doi.org/10.1520/MPC20170128 (Accessed April 21, 2024)
Created April 26, 2018, Updated January 27, 2020