Effects of loading rate, notch geometry and loading mode on the local cleavage fracture stress of a C–Mn steel |
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Authors: | G Z Wang Y L Wang |
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Affiliation: | (1) School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai, 200237, China;(2) State Key Laboratory of Advanced Non-Ferrous Metal Materials, Lanzhou University of Technology, Lanzhou, 730050, China |
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Abstract: | In this work, notched specimens with two notch geometries were tested in two loading modes (four-point bending (4PB) and three-point
bending (3PB)) at various loading rates at a temperature of − 110°C for a C–Mn steel. An elastic–plastic finite-element method
(FEM) is used to determine the stress distributions ahead of notches. By accurately measuring the distances of the cleavage
initiation sites from the notch roots, the local cleavage fracture stress σ
f is measured. The results obtained and combining with previous studies by the authors show that the local cleavage fracture
stress σ
f is closely related to the cleavage fracture mechanism (critical events) in steels. The σ
f values do not change with loading rate, notch geometry and loading mode, as long as the critical event of cleavage fracture
does not change at various testing conditions. The σ
f is mainly determined by the steel microstructure, and its scatter is mainly caused by the size distribution of the weakest
constituent in steels (ferrite grain or pearlite colony with large sizes and large second phase particles) and the change
of the critical events in cleavage process. The σ
f can characterize the intrinsic toughness of steels and may be used in a “local approach” model for assessing integrity of
flawed structures. The σ
f values could be measured by both 4PB and 3PB tests. |
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Keywords: | Local cleavage fracture stress Loading rate Notch geometry Loading mode FEM C– Mn steel |
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