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

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DSTO-RR-0208 Figure 6: <strong>The</strong> glass bead peened area from drawing 74A32405 Sh 3 Revision U is shown by the hatching marks. <strong>The</strong> original peening area is the cross-hatched markings. This figure when compared with figure 4 (revision L) shows the increased peened area on the FS488 bulkhead as F/A-18 production increased. 10
DSTO-RR-0208 RAAF F/A-18 aircraft A21-1 through to A21-18 and A21-101 through to A21-114 were manufactured with a 143-pr<strong>of</strong>ile flange bulkhead. This 143-pr<strong>of</strong>ile flange was reworked to 6 inch pr<strong>of</strong>ile flange during Engineering Change Program 45 (ECP45), along with the longeron recess area, Figure 7. <strong>The</strong> RAAF contractor, with RAAF agreement, and acting on advice from AMRL derived from early research (Clayton and Clark 1988), used a procedure which differed from the Original Equipment Manufacturer (OEM) specification (Anderson, 1990; Barter, 1990 and Stanier, 1990). <strong>The</strong> OEM process calls for the rework peening to be performed over the original vendor peening. 6"radius pr<strong>of</strong>ile F143 pr<strong>of</strong>ile Shaded areas indicate the F143 flange pr<strong>of</strong>ile segments removed during the 6" radius pr<strong>of</strong>ile modification. Figure 7: A schematic showing the location <strong>of</strong> <strong>of</strong>fcuts from ECP45 delivered to AMRL from 32 aircraft. In 32 RAAF F/A-18 aircraft which went through ECP 45, the whole area originally peened by the vendor was polished before re-peening. <strong>The</strong> critical area <strong>of</strong> the bulkhead was to be polished to a surface roughness <strong>of</strong> 0.2 micrometres (8 microinches) as defined by ASME B46- 1985. This involved an initial dry polish with 250# Aluminium oxide abrasive paper, then a final polish with P400 (360#) Aluminium oxide abrasive paper, Figure 8. A total loss glass bead system was also used instead <strong>of</strong> a recycled and filtered glass bead system, Figure8. Summarising: 1. AMRL rework process: OEM peen → polish → total loss glass bead re-peen. 2. OEM rework process: OEM peen → OEM peen (peen directly over original peen) 11
Page 1 and 2: The Effect
Page 3: The Effect
Page 7: Contents 1. INTRODUCTION ..........
Page 10 and 11: DSTO-RR-0208 extension method has n
Page 12 and 13: DSTO-RR-0208 Figure 2: A graph illu
Page 14 and 15: DSTO-RR-0208 the total life is long
Page 16 and 17: DSTO-RR-0208 Figure 4: This figure
Page 20 and 21: DSTO-RR-0208 Figure 8: The<
Page 22 and 23: DSTO-RR-0208 crack initiate from an
Page 24 and 25: DSTO-RR-0208 Figure 10: SEM photogr
Page 26 and 27: DSTO-RR-0208 550 USN Spectrum (ST-1
Page 28 and 29: DSTO-RR-0208 Table 2: Four point be
Page 30 and 31: DSTO-RR-0208 Figure 15b: Scanning e
Page 32 and 33: DSTO-RR-0208 Research by Fair et al
Page 34 and 35: DSTO-RR-0208 3.2.3 Summary
Page 36 and 37: DSTO-RR-0208 Peak Spectrum Stress (
Page 38 and 39: DSTO-RR-0208 Figure 21b: A typical
Page 40 and 41: DSTO-RR-0208 10 Crack Depth (mm) 1
Page 42 and 43: DSTO-RR-0208 Table 7: The</
Page 44 and 45: DSTO-RR-0208 200 180 160 8A ALMEN 6
Page 46 and 47: DSTO-RR-0208 Figure 28: A schematic
Page 48 and 49: DSTO-RR-0208 Table 9: Residual Stre
Page 50 and 51: DSTO-RR-0208 Like all the structura
Page 52 and 53: DSTO-RR-0208 Y470 X19 pocket Peened
Page 54 and 55: DSTO-RR-0208 4. Discussion
Page 56 and 57: DSTO-RR-0208 5. Conclusion 1. <stro
Page 58 and 59: DSTO-RR-0208 Clayton J.Q. and Clark
Page 60 and 61: DSTO-RR-0208 Sharp P.K. and Clark G
Page 62 and 63: DSTO-RR-0208 Figure 23: The
Page 64 and 65: DSTO-RR-0208 A.4. Surface Roughness
Page 66 and 67: UK Defence Research Information Cen
Page 68:
Page classification: UNCLASSIFIED D
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The Effect of Peening on the Fatigue Life of 7050 Aluminium Alloy

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