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Introduction
The existence of any geometric irregularities in any shape or form can on a
loaded mechanical part or even a structural member can hinder the normal flow of
stress trajectories of that specimen.
This could cause stresses to crowd together and
increase or decrease stresses making them not equal to nominal value calculated by
conventional mechanics and materials formulas that have been created.
This
experiment can be used in many settings dealing with different types of materials.
(For example normal characteristics in different types of steel such as ultimate
tensile strength or yield strength)
Purpose
The purpose of this experiment is to model the existence of stress and strain
concentrations of geometric discontinuities in the cantilever beam.
Also we must
acquire the approximate measure of the elastic stress concentration factor K
t
.
In this experiment the discontinuity can be measured from the circular hole drilled on the
centerline of the bar.
Theory
Modulus of elasticity is expressed as the compression, tension, and elasticity of
the material before it hits its point of deformation.
The flexure formula makes it possible
to derive the stress of the material: (at section A)
a
=
=
where:
M=bending moment at gage centerline, inlbs (Nm)
c= semithickness of beam, in (m)
l=moment of inertia of beam cross section, in^4 (m^4)
P= load, lbf (N)
L= effective beam length, in (m)
B= beam width, in (m)
T= beam thickness, in (m)
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 Spring '11
 SMITH

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