A unified fracture criterion considering stress state dependent transition of failure mechanisms in bcc steels at -196 °c

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2022-09
Major/Subject
Mcode
Degree programme
Language
en
Pages
22
Series
INTERNATIONAL JOURNAL OF PLASTICITY, Volume 156
Abstract
The fracture properties of a high-strength steel with a body-centered cubic (bcc) crystal structure have been characterized at -196 °C by performing tensile tests with different specimen geometries, three-point bending tests using Charpy specimens, and fracture mechanics tests, covering a broad range of stress states under quasi-static conditions. Both strength and ductility of the bcc steel are significantly increased when the temperature is decreased from room temperature to -196 °C. Enormous plasticity occurs in the material during tensile tests using various specimens at -196 °C, while macroscopic brittle fracture takes place in high triaxiality scenarios. A stress state dependence of ductile to brittle transition properties is observed, as the failure mechanisms at -196 °C change from cleavage fracture to shear failure with decreasing stress triaxiality. A unified stress-state-dependent fracture criterion, which considers the transition of failure mechanisms, is proposed to describe the fracture properties of similar bcc materials at cryogenic temperatures. The threshold triaxiality at which the transition of failure mechanisms takes place is a material property that is determined by the strain hardening capacity and fracture strength. In addition, a probabilistic formulation relying on the extreme value distribution has been incorporated into the model to render the statistical nature of cleavage fracture.
Description
Funding Information: thyssenkrupp Steel Europe AG is gratefully acknowledged for materials supply and financial support. Simulations were performed with computing resources granted by RWTH Aachen University under project rwth0241. Publisher Copyright: © 2022 The Author(s).
Keywords
Cleavage fracture, Fracture criterion, Shear fracture, Stress states, Threshold triaxiality
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Citation
Shen, F, Münstermann, S & Lian, J 2022, ' A unified fracture criterion considering stress state dependent transition of failure mechanisms in bcc steels at -196 °c ', INTERNATIONAL JOURNAL OF PLASTICITY, vol. 156, 103365 . https://doi.org/10.1016/j.ijplas.2022.103365