The ratio of lateral strain to linear strain is known as Poisson’s ratio.
Poisson’s ratio = Lateral strain (or) Transverse strain / Linear or primary strain = 1/m
Where
m – Constant and its value varies between 3 and 4 for different materials.
Poisson’s ratio for some of the common materials
Aluminum – 0.330
Brass – 0.340
Bronze – 0.350
Cast iron – 0.270
Concrete – 0.200
Copper – 0.355
Steel – 0.288
Stainless steel – 0.305
Wrought iron – 0.278