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Shot peening is a cold working process in which small
spherical media called shot bombard the surface of a
part. During the shot peening process, each piece of
shot that strikes the material acts as a tiny peening
hammer, imparting to the surface a small indentation
or dimple. To create the dimple, the surface of the
material must yield in tension. Below the surface, the
material tries to restore its original shape, thereby
producing below the dimple, a hemisphere of cold-worked
material highly stressed in compression.
Nearly all fatigue and stress corrosion failures originate
at the surface of a part, but cracks will not initiate
or propagate in a compressively stressed zone. Because
the overlapping dimples from shot peening create a uniform
layer of compressive stress at metal surfaces, shot
peening provides considerable increases in part life.
Compressive stresses are beneficial in increasing resistance
to fatigue failures, corrosion fatigue, stress corrosion
cracking, hydrogen assisted cracking, fretting, galling
and erosion caused by cavitation. The maximum compressive
residual stress produced just below the surface of a
part by shot peening is at least as great as one-half
the yield strength of the material being shot peened.
Shot Peening Video
In most modes of long-term failure, the common denominator
is tensile stress. Tensile stresses attempt to stretch
or pull the surface apart and may eventually lead to
crack initiation. Because crack growth is slowed significantly
in a compressive layer, increasing the depth of this
layer increases crack resistance. Shot peening is the
most economical and practical method of ensuring surface
residual compressive stresses. For applications that
require deeper residual compressive stresses than those
provided by shot peening, Metal Improvement Company's
laser peening process imparts a layer of beneficial
compressive stress that is four times deeper than that
attainable from conventional shot peening treatments.
Shot peening also can induce the aerodynamic curvature
in metallic wing skins used in advanced aircraft designs.
Additional applications for shot peening include work
hardening through cold work to improve wear characteristics,
closing of porosity, improving resistance to intergranular
corrosion, straightening of distorted parts, surface
texturing and testing the bond strength of coatings.
Metal Improvement Company engineering specialists can
help you address the engineering challenges that shot
peening can answer. Metal Improvement Company's shot
peening facilities employ the latest state-of-the-art
processing capabilities for shot peening components
of diverse shapes, sizes and materials under rigidly
controlled conditions.
To
download data sheets, technical information and article
reprints
about MIC Shot Peening services, click here!
To
locate the MIC Shot Peening Facility nearest you, click
here.
If
you would like to receive information about MIC, and
any services
we provide, click here.
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