Engineering curve for mild steel for tension under static-loading
OA – Straight line (proportional region, Hooks law is valid)
OB – Elastic region
BC’ – Elasto plastic region
CD – Perfectly plastic region
DE – Strain hardening
EF – Necking region
A – Limit of proportionality
B – Elastic limit
C’ – Upper yield point
C – Lower yield point
D – Strain hardening starts
E – Ultimate stress
F – Fracture point
Limit of proportionality
it is the point at which the stress-strain curve ceases to be a straight line.
When a material behaves elastically and exhibits a linear relationship between stress and strain, it’s called linearly elastic. In this stress (σ) is directly proportional to strain (ϵ)Where, σ = Stress, ϵ=Strain
E = Young’s Modulus of elasticity
It is the point in the stress-strain curve up to which the materials remain elastic. Up to this point, there is no permanent deformation after the removal of load.
It is the region of the stress-strain curve between the elastic limit and point of rupture.
This point is just beyond the elastic limit, at which the specimen undergoes an appreciable increase in length without further increase in the load.
It is the stress corresponding to the failure point ‘F’ of the stress-strain curve.
It is the stress necessary to cause a permanent extension equal to a defined percentage of the gauge length.
The slope of OA = Modulus of elasticity (Young’s Modulus) It is the constant of proportionality which is defined as the intensity of stress that causes unit strain.
Plastic strain is 10 to 15 times elastic strain
- Fracture strain(ϵf)depends on the percentage of carbon in the steel.
- When carbon percentage increases then fracture strain decreases and yield stress increases.
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