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The behaviour of fatigue crack
growth at room temperature was gotten from 4140 parent
steel. The parent steel was heat treated, as-welded and
material under R", 0 constant amplitude loading and single
tensile overloads with an over load ratio of 2.5. The
purpose of this research is to contribute to the needed
information for safe design and service life of weldments,
subjected to both constant amplitude and single tensile
overloads. The data are essentially log-log linear and hence
satisfy the region II Paris equation, the overload cycles to
failure for a given R ratio fell within a factor of about
3.0 or less for all material test conditions, this again is
a rather small variation between materials. The number of
cycles of retardation, NR, varies from about 3.0 x 110 to
5.0 x 110 cycles. This represents fatigue crack growth life
increases from about 300 to 500% for R ≈ 0. This indicates
that all the material conditions investigated responded
favorably to the single tensile overloads. All four material
conditions had the same constant amplitude fatigue crack
growth resistance in the Paris log-log linear region.
Differences in fatigue life and fatigue crack growth rates
were within a factor or two.
Keywords: Crack, Steel, Growth, Fractograph, Low Alloy
Steel, Heat Affected Zone (HAZ)
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