Onset of Plasticity via Relaxation Analysis (OPRA)

In crystalline metals and alloys, plasticity occurs due to the movement of mobile dislocations and the yield stress for engineering applications is traditionally quantified based on strain. The onset of irreversible plasticity or “yielding” is generally identified by a deviation from linearity in th...

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Bibliographic Details
Published in:Experimental mechanics 2016-07, Vol.56 (6), p.1095-1107
Main Authors: Pandey, A., Wheeler, R., Shyam, A., Stoughton, T. B.
Format: Article
Language:English
Subjects:
Biomedical Engineering and Bioengineering
Characterization and Evaluation of Materials
Control
Dynamical Systems
elastic limit
Engineering
Lasers
MATERIALS SCIENCE
microtesting
mobile dislocation
Optical Devices
Optics
Photonics
Solid Mechanics
Vibration
yield stress
yield surface
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Summary:In crystalline metals and alloys, plasticity occurs due to the movement of mobile dislocations and the yield stress for engineering applications is traditionally quantified based on strain. The onset of irreversible plasticity or “yielding” is generally identified by a deviation from linearity in the stress-strain plot or by some standard convention such as 0.2 % offset strain relative to the “linear elastic response”. In the present work, we introduce a new methodology for the determination of the true yield point based on stress relaxation. We show experimentally that this determination is self-consistent in nature and, as such, provides an objective observation of the very onset of plastic flow. Our designation for yielding is no longer related to the shape of the stress-strain curve but instead reflects the earliest signature of the activation of concerted irreversible dislocation motion in a test specimen under increasing load.
ISSN:0014-4851
1741-2765
DOI:10.1007/s11340-016-0152-3