The term stress is used to express the loading
in terms of force applied to a certain crosssectional area of an object.
From the perspective of loading, stress is the
applied force or system of forces that tends to
deform a body.
From the perspective of what is happening
within a material, stress is the internal
distribution of forces within a body that
balance and react to the loads applied to it.
The stress distribution may or may not be uniform,
depending on the nature of the loading condition.
Simplifying assumptions are often used to represent
stress as a vector quantity for many engineering
calculations and for material property determination. The
word “vector” typically refers to a quantity that has a
"magnitude" and a "direction".
Simple Stresses are mainly of 4 types:
1.Axial or Normal Stress
2. Shear Stress
4.Thin-walled Pressure Vessel
Axial Stress :
Axial or normal stress is defined as the stress
component at a point in a structure which is
perpendicular to the reference plane.
Axial loads pass through the centroid of the section
and must be perpendicular to the reference plane.
The axial forces upon the structure are typically
stretching force or compression force, depending on
when the bar is stretched, the resulting stress are
tensile stress, if the bar is compressed, the stress
are compressive stress.
the stress σ (sigma) acts in the direction
perpendicular to the cut surface, that is referred
as normal stress or Axial stress.
sign convention of the normal stresses are :
tensile stress as positive and compressive stress
Unit of stress :
*SI unit : N / m2 (Pa, Pascal), N / mm2 (MPa)
Types of Axial stress :
1. Tensile stress :
It is customary to refer to axial stress that cause
traction or tension or extends on the surface of a cut
known as Tensile stress.
Example : tension cables on a bridge.
2. Compressive stress :
Axial stresses those are pushing against the cut are
known as Compressive stress.
Example : columns in architecture and the steel structure
of high rise building.
Members should be straight.
Axial force P must act through the centroid of
the cross-section and must be perpendicular
reference to the plane. Otherwise, the bar will
bend and a more complicated analysis is needed.
The stress must be uniformly distributed over the
Material should be homogeneous (same
throughout all parts of the bar).
Deformation is uniform. That is, we assume that
we can choose any part of the bar to calculate the