The Effect of Peening on the Fatigue Life of 7050 Aluminium Alloy

DSTO-RR-0208
Figure 23: <strong>The</strong> standard Almen strips and process <strong>of</strong> measurement (Shot <strong>Peening</strong> Applications 7 th
Edition).
<strong>The</strong>re are three standard Almen strips currently in use; “A” strip 0.051inch thick, “C” strip
0.094 inch thick and “N” strip 0.031inch thick. <strong>The</strong> approximate relationship between the
three Almen strip types is 3N= A= 0.3C. <strong>The</strong> useable range <strong>of</strong> curvature on an Almen strip
is 0.004 to 0.024 inch.
A.3. Saturation Curve
An Almen arc height is not properly termed intensity unless saturation is achieved. In
order to measure Almen saturation, an intensity curve must be developed. Saturation is
defined as the earliest point on the curve where doubling the exposure time produces no
more than ten percent (10%) increase in arc height.
Arc Height
Less than 10% increase
T 2T Exposure Time
Figure 24: <strong>Peening</strong> saturation curve theory (Shot <strong>Peening</strong> Applications, 7 th Edition).
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