Lateral Strain

Strain which is perpendicular in direction of applied load is called as "Lateral Strain or Secondary Strain".

Mathematically,

Lateral Strain = ^{Change in length in lateral dimension} / _{Original lateral dimension}

For rectangular bar -

Lateral Strain = ^δb / _b or ^δt / _t

Where,
             δb - change in width or breadth and b - original width or breadth,
             δt - change in thickness and t - original thickness.

Consider a bar as shown in fig. bar having length(L), width(b) and thickness(t) subjected to pulling force(P) Due to this loading length of bar increases while decrease in width and thickness take place. Therefore linear strain is positive and lateral strain is negative. In this case,
Linear Strain = e = ^+δL / _L
Lateral Strain = ^-δb / _b or ^-δt / _t

For circular bar -

Lateral Strain = ^δd / _d

Where,
             δd - change in diameter and d - original diameter.