WHAT IS STRAIN?
Strain is the ratio of the change in length caused by
the applied force, to the original length.
Axial strain in a longitudinal member ( a
pole, column, strut or cable, for example) would
be the increase in length over the original length
when it is pulled (tensile strain) or pushed
An axial bar of length L, and cross-sectional
area A, subjected to tensile force P, elongates
by an amount, ∆. The change in length divided
by the initial length is termed as Axial Strain
or simply strain (∆/L). The symbol used for
engineering strain is E (epsilon).
E = ∆/L
where ∆ is the
deformation and L
is the original
Thus, strain(E) is
1.Strain is positive in tension (D>0 means e<0) and
negative in compression (D<0)
2.Strain is a non-dimensional length - a fraction.
Because strain is small, it is often given as a
percentage by multiplying by 100%: e.g., e = 0.003
A stress that tends to change the length of a body in axial
direction. Two types of Axial stress:
Tensile stress is axial stress that tends to cause a body to
become longer along the direction of applied force.
Compressive stress is axial stress that tends to cause a
body to become shorter along the direction of applied
BENDING MOMENT STRESS
An internal tensile or compressive longitudinal
stress developed in a beam in response to
curvature induced by an external load.
TYPES OF STRAIN:
Tensile strain: When we apply a tensile force on
a body its length increases. The ratio of increase
in length to the original length.
Tensile strain εt = L – L0 / L
Where L = Original length
L0 = new length
Compressive strain: When we apply a
compressive force on a body its length
decreases. The ratio of decrease in length to the
original length is called compressive strain.
Compressive strain = εc = L – L0 / L
Where, L = Original length
L0 = new length