English: Illustration of offset yield point. Key:

1: True elastic limit

2: Proportionality limit

3: Elastic limit

4: Offset yield strength, usually defined at e=0.2%

σ: Engineering stress

ε: Engineering strain

A: Undeformed cross-sectional area

F: Uniaxial load

L: Undeformed length

l: Elongation

Reference: G. Dieter, Mechanical Metallurgy, McGraw-Hill, 1986