# Proportionality of stress & strain on stress-strain curve - Basic Mechanical Engineering

Q.  In stress-strain diagram, up to proportional limit ______
- Published on 01 Sep 15

a. stress is inversely proportional to strain
b. force is directly proportional to displacement
c. stress is directly proportional to strain
d. strain is directly proportional to stress

ANSWER: stress is directly proportional to strain

#### Discussion

• Sravanthi   -Posted on 06 Nov 15
Proportionality limit:

- The relation between gradually increasing tensile force and the deformation of a material is plotted on stress-strain diagram.

- Hooke's law states that stress is directly proportional to strain only upto proportional limit. At this point, the stress-strain curve deviates from straight line.

- σ = Ee ---------( upto proportionality limit)

here,
E = modulus of elasticity ( It is measured in N/mm2)
e = strain
σ = stress ( It is measured in N/mm2)

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