True Stress
Definition
The force divided by the instantaneous (current) cross-sectional area: σₜ = F/A. Related to engineering stress by σₜ = σₑ(1 + εₑ) for uniform deformation. More accurate for large strains.
Practical Note
True stress continues to increase during necking until fracture, while engineering stress decreases. Use true stress-strain for forming simulations and large-deformation analysis.