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

DSTO-RR-0208
Table 8: Coupon fatigue life results. Five coupons were tested per condition.
Base Line Peen Peen + Patch Repair
Process
Coupon 1 60.85 80.19
Coupon 2 71.19 70.54
Coupon 3 108.54 55.02
Coupon 4 62.58 58.98
Coupon 5 63.58 66.87
Log Average 71.1 66.1
A statistical comparison was made <strong>of</strong> the two process sets, which showed that there was a
97.5% probability <strong>of</strong> them being from a single population. To further confirm this result,
surface residual stress analysis was performed on the coupons. Table 9 compares the base
line residual stress with the residual stress from just the surface treatment (ie missing step 7
adhesive cure) and the residual stress for the complete process.
Fatigue Life (programs)
120
100
80
60
40
20
0
max
min
BL
RRP
Figure 29: Column graph comparing the base line test results with the repair process. Note how the
range <strong>of</strong> repaired process coupons falls in the range <strong>of</strong> baseline coupon failures
39