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· Once a neck
begins to form in the
sample, the stress field in the neck region is complex and the stages of ductile
fracture
occurs under the influence of these combined multi-axial stresses.
· The tensile stress (longitudinal)
has its maximum value at the center of the sample, drops off at intermediate
radii and then increases at the outer surface. For an isotropic
material,
τmax = σ/2
, and
the shear stress is also large at the center and at the outer surface.
The radial and circumferential stresses decrease monotonically from the center
to the surface.
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From:
Hayden, Moffatt, and Wulff, "Structure and Properties of Materials,"
Wiley (1967) |
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