Engineering and working stress

Engineering stress

  • For most stress/strain diagrams, stress appears to fall off near the end (during the necking down phase). This should NOT happen.
  • Though, it is shown on most stress/strain diagrams as it does not show true stress, but engineering stress.
  • Engineering stress is calculated using the ORIGINAL cross sectional area, even though the cross sectional area reduces during necking down. This explains why the stress drops.
  • This is done for ease of calculation, otherwise the cross sectional area would have to be measured continuously.

Working stress