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When
a crack or inclusion of different elastic modulus is present in a material
the stress in the region of the defect is larger than the average stress
applied to the material, a stress concentration.
The
diagram illustrates the efect of an elliptical crack on the local stress
at the crack tip. The crack-tip radius is, r,
and the total crack length of the bulk crack is, 2a, or the surface crack,
a. For this case, the maximum stress at the crack tip is given by: sm
= 2s0(a
/ r)0.5.
Plot (b) illustrates how the stress drops of to the mean stress as a function
of distance from the crack tip. The curve shown drops off as (1 / x). |
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