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Title: 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 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. Lastly, 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.
 [1] ;  [2] ;  [3] ;  [4]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division; Rolls Royce LG Fuel Cell Systems Inc., North Canton, OH (United States)
  2. MicroTesting Solutions LLC, Columbus, OH (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division
  4. General Motors Research and Development Center, Warren, MI (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Experimental Mechanics
Additional Journal Information:
Journal Volume: 56; Journal Issue: 6; Journal ID: ISSN 0014-4851
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Fossil Energy (FE); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V); Work for Others (WFO)
Country of Publication:
United States
36 MATERIALS SCIENCE; yield stress; elastic limit; yield surface; microtesting; mobile dislocation
OSTI Identifier: