Friday, 25 November 2022

LATERAL STRAIN, LONGITUDINAL STRAIN AND POISSON'S RATIO

 

LATERAL STRAIN, LONGITUDINAL STRAIN AND POISSON'S RATIO

Longitudinal strain: 

Whenever the bar is subjected to the axial load, there will be an increase in the length of the
 the bar along the direction of loading. Therefore the longitudinal strain is defined as the ratio
of increase in the length of the bar in the direction of the applied load to that of the original
 length (gauge length).

i.e, e = dL/L
where
e= longitudinal strain
dl= increase in length
L = gauge or original length


Lateral strain: Whenever the bar is subjected to the axial load, there will be a decrease
 in the dimensions of the bar in the perpendicular direction of loading. Therefore lateral 
strain is defined as the ratio of decrease in the length of the bar in the perpendicular direction 
of applied load to that of the original length (gauge length).
i.e, e = dB/B or dD/D

where
e= lateral strain
dd= decrease in depth
D= gauge or original depth
db= decrease in breadth
B = gauge or original breadth

Poisson’s ratio:  The ratio of lateral strain to that of the longitudinal strain is termed Poisson's ratio 
and it is represented by ϻ or 1/m.


i.e, ϻ or 1/m =  lateral strain/longitudinal strain

The value of the Poisson’s ratio for most materials lies between 0.25 and 0.33.

Er. SP.ASWINPALANIAPPAN., M.E.,(Strut/.,)
Structural Engineer

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