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Title: The mechanisms of ductile rupture

Abstract

One of the most confounding controversies in the ductile fracture community is the large discrepancy between predicted and experimentally observed strain-to-failure values during shear-dominant loading. Currently presented solutions focus on better accounting for how the deviatoric stress state influences void growth or on measuring strain at the microscale rather than the macroscale. While these approaches are useful, they do not address a significant aspect of the problem: the only rupture micromechanisms that are generally considered are void nucleation, growth, and coalescence (for tensile-dominated loading), and shear-localization and void coalescence (for shear-dominated loading). Current phenomenological models have thus focused on predicting the competition between these mechanisms based on the stress state and the strain-hardening capacity of the material. However, in the present study, we demonstrate that there are at least five other failure mechanisms. Because these have long been ignored, little is known about how all seven mechanisms interact with one another or the factors that control their competition. These questions are addressed by characterizing the fracture process in three high-purity face-centered cubic (FCC) metals of medium-to-high stacking fault energy: copper, nickel, and aluminum. These data demonstrate that, for a given stress state and material, several mechanisms frequently work together inmore » a sequential manner to cause fracture. The selection of a failure mechanism is significantly affected by the plasticity-induced microstructural evolution that occurs before tearing begins, which can create or eliminate sites for void nucleation. At the macroscale, failure mechanisms that do not involve cracking or pore growth were observed to facilitate subsequent void growth and coalescence processes. Even though the focus of this study is on damage accumulation in pure metals, these results are also applicable to understanding failure in engineering alloys.« less

Authors:
 [1];  [1];  [1]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1524207
Report Number(s):
SAND-2018-5461J
Journal ID: ISSN 1359-6454; 663415
Grant/Contract Number:  
AC04-94AL85000
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 161; Journal Issue: C; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Ductile fracture; Damage nucleation; Failure mechanism; Strain localization; Shear

Citation Formats

Noell, Philip J., Carroll, Jay D., and Boyce, Brad L. The mechanisms of ductile rupture. United States: N. p., 2018. Web. doi:10.1016/j.actamat.2018.09.006.
Noell, Philip J., Carroll, Jay D., & Boyce, Brad L. The mechanisms of ductile rupture. United States. doi:10.1016/j.actamat.2018.09.006.
Noell, Philip J., Carroll, Jay D., and Boyce, Brad L. Thu . "The mechanisms of ductile rupture". United States. doi:10.1016/j.actamat.2018.09.006. https://www.osti.gov/servlets/purl/1524207.
@article{osti_1524207,
title = {The mechanisms of ductile rupture},
author = {Noell, Philip J. and Carroll, Jay D. and Boyce, Brad L.},
abstractNote = {One of the most confounding controversies in the ductile fracture community is the large discrepancy between predicted and experimentally observed strain-to-failure values during shear-dominant loading. Currently presented solutions focus on better accounting for how the deviatoric stress state influences void growth or on measuring strain at the microscale rather than the macroscale. While these approaches are useful, they do not address a significant aspect of the problem: the only rupture micromechanisms that are generally considered are void nucleation, growth, and coalescence (for tensile-dominated loading), and shear-localization and void coalescence (for shear-dominated loading). Current phenomenological models have thus focused on predicting the competition between these mechanisms based on the stress state and the strain-hardening capacity of the material. However, in the present study, we demonstrate that there are at least five other failure mechanisms. Because these have long been ignored, little is known about how all seven mechanisms interact with one another or the factors that control their competition. These questions are addressed by characterizing the fracture process in three high-purity face-centered cubic (FCC) metals of medium-to-high stacking fault energy: copper, nickel, and aluminum. These data demonstrate that, for a given stress state and material, several mechanisms frequently work together in a sequential manner to cause fracture. The selection of a failure mechanism is significantly affected by the plasticity-induced microstructural evolution that occurs before tearing begins, which can create or eliminate sites for void nucleation. At the macroscale, failure mechanisms that do not involve cracking or pore growth were observed to facilitate subsequent void growth and coalescence processes. Even though the focus of this study is on damage accumulation in pure metals, these results are also applicable to understanding failure in engineering alloys.},
doi = {10.1016/j.actamat.2018.09.006},
journal = {Acta Materialia},
issn = {1359-6454},
number = C,
volume = 161,
place = {United States},
year = {2018},
month = {9}
}

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