Definitions of Stress, Strain, Modulus of Elasticity, Poisson’s Ratio
1. Stress (tensile or compressive)
P
(MPa)
A

2. Strain
a. Elongation or shortening ()
b. Strain


L
(dimensionless, or
mm/mm)
3. Modulus of Elasticity (E, material
property)
E


Obtained from the elastic section of stress
strain curve
 based on Hooke’s Law
 Slope of the straight line segment
4. How to calculate elongation/shortening of a bar:
5. Poisson’s ratio (, material property)
a. Lateral strain
y 
y
Ly
b. Poisson’s ratio
 
y
(dimensionless)
x

PL
EA