True Strain
Definition
The natural logarithm of the ratio of current to original length: εₜ = ln(L/L₀) = ln(1 + εₑ). Also called logarithmic or natural strain. Additive for sequential deformations.
Practical Note
For small strains (< 5%), true and engineering strain are nearly equal. True strain is preferred for large-deformation analysis because sequential strains can be added directly.