True Stress-Strain Curve on the Log Scale: Which portion is the plastic region?

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Discussion Overview

The discussion centers around identifying the elastic and plastic regions on a true stress-strain curve presented on a logarithmic scale. Participants seek clarification on how to distinguish these regions, particularly in the context of a specific graph.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant expresses difficulty in identifying the elastic and plastic regions on the curve and requests further assistance.
  • Another participant references Hooke's law to suggest that elastic action precedes plastic action when stretching a specimen.
  • A subsequent reply confirms that the elastic region comes first but questions whether the differentiation between the two regions can be made based on the provided figure.
  • Another participant argues that according to Hooke's law, stress is proportional to strain in the elastic region, but notes that the graph shows a straight line on a log-log scale, implying that stress and strain are not proportional, which complicates the identification of the elastic region.
  • This participant concludes that if the graph is accurate, the elastic region cannot be identified as it is not represented on the graph.

Areas of Agreement / Disagreement

Participants express differing views on the identification of the elastic and plastic regions, with some asserting that the elastic region should be identifiable while others contend that the graph does not allow for such differentiation. The discussion remains unresolved regarding the clarity of the graph and the representation of the regions.

Contextual Notes

The discussion highlights potential limitations in the graph's representation, including the implications of using a logarithmic scale and the assumptions regarding proportionality in the elastic region.

gikiian
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My math is a little weak, so I'm having a hard time finding the elastic and plastic regions on this curve. Any further help will also be appreciated!

Strain-hardening.jpg
 
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Remember Hooke's law. What comes first, elastic or plastic action, when stretching a specimen?
 
The elastic region comes first. But can you differentiate between the two in the figure?
 
Hooke's law says that in the elastic region, stress is proportional to strain.

In your graph you have a strainght line on a log log scale (not a linear scale) but the stress and strain are not proportional.

If your graph is drawn correctly, you can't find the elastic region because it isn't shown on the graph!
 

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