Strength of Material (Part-4) (General Engineering) (SSC JE)

The area under the stress-strain plot (product of stress and strain) represents energy required of cause failure.
• Area under stress strain curve till fracture point defines material toughness.

In this phenomena, increase in stress with in increase in strain beyond yielding occurs.
During strain hardening:-
- Stress- strain diagram has positive slope
- Increased resistance to further deformation
- Martial undergoes change in atomic and crystalline structure.
Note:- The rise in the curve is called strain hardening.

The ratio of transverse strain to the longitudinal strain under an axial load is known as poisson's ratio (µ).
µ = Transverse strain/Longitudinal strain

Buckling load–The maximum limiting load at which the column tends to have displacement or tends to buckle is called buckling or crippling load.

• In structural engineering, buckling is the sudden change in shape (deformation) of a structural component under load, such as the bowing of a column under compression or the wrinkling of a plate under shear.

If a substance resists shear stress by elastic deformation then the substance is solid.
• Elastic deformation is a change of the shape of the body as a reaction to applied stress.
This deformation is only temporary and once the stress is released, the undeformed shape of the body is restored.

The stress required to cause actual fracture of material is called the ultimate stress.
σᵤ = Ultimate load/Area

The critical load is the greatest load, that will not cause lateral deflection (buckling). For loads greater than the critical load, the column will deflect laterally. The critical load puts the column in a state of unstable equilibrium.