MIND GROW Magazine

Properties of Matter – Stage 1 (Page 5)

Stress–Strain Curve, Elastic Limit & Breaking Point (IIT-JEE Focus)

1. Stress–Strain Curve (General)

The stress–strain curve represents how a material responds when subjected to increasing stress.

(Graph: Stress on Y-axis, Strain on X-axis)

Initial region is linear
Beyond elastic limit, permanent deformation occurs

2. Important Points on Stress–Strain Curve

O–A : Proportional limit (Hooke’s law valid)
A–B : Elastic region
B : Elastic limit
C : Yield point
D : Ultimate tensile stress
E : Breaking point

IIT Tip:
Hooke’s law is valid only up to proportional limit, not till elastic limit.

3. Elastic Limit

Elastic limit is the maximum stress up to which the body completely regains its original shape after removal of force.

No permanent deformation below elastic limit
Material behaves elastically

4. Yield Point

Yield point is the stress beyond which large strain occurs without increase in stress.

Clearly visible in ductile materials
Not well-defined for brittle materials

5. Ultimate Tensile Stress

Maximum stress that a material can withstand before necking begins.

Ultimate Stress = Maximum Load / Area

Maximum point on stress–strain curve
After this, material weakens

6. Breaking Stress

Breaking stress is the stress at which material fractures.

Less than ultimate stress
Fracture occurs suddenly in brittle materials

Important:
Breaking stress ≠ Strength ≠ Elasticity

7. Ductile vs Brittle Materials

Ductile	Brittle
Large plastic deformation	Very small plastic region
Clear yield point	No yield point
Example: Copper, Steel	Example: Glass, Cast iron

8. Resilience

Ability of a material to absorb energy in elastic region.

Modulus of Resilience = Elastic energy per unit volume

Stage 1 – Page 5 Summary

Stress–strain curve regions
Elastic limit & yield point
Ultimate stress vs breaking stress
Ductile vs brittle materials
Resilience concept

Stage 1 – Page 5 Completed ✅
Next: Poisson’s Ratio, Bulk Modulus & Volume Elasticity – Page 6

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