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

DSTO-RR-0208
Peak Spectrum Stress (MPa)
420
415
410
405
400
395
390
385
Comparison <strong>of</strong> Fatigue Lives between
Ceramic Bead <strong>Peening</strong> and Glass Bead <strong>Peening</strong>.
Hand Polish
Aircraft glass bead peen simulation
Rework peen directly over original peen
Rework peen over polished surface
Ceramic bead rework peen over polished surface
380
6000 8000 10000 30000
Fatigue Life (Simulated Flight Hours)
Figure 20: Experimental results comparing the fatigue lives <strong>of</strong> a number <strong>of</strong> different localised rework
peening processes. <strong>The</strong> ceramic beads where manufactured from aluminium oxide. <strong>The</strong>
beads were very spherical, had a small variation in diameter compared to glass and very
hard and heavy.
Table 5 also displays the surface roughness results and the residual stress results for each <strong>of</strong>
the different peening rework processes. <strong>The</strong> residual compressive stress is a factor in the
improved fatigue life due to peening, and AMRL and Monash University (Victoria), built a
rig which could hold the test specimens for x-ray residual stress testing. This rig simplified
the process immensely, meaning that residual stress results could be obtained easily and
with improved accuracy.
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