Figure 5 BRSW simulation on cracked aircraft pressured fuselage repair
with repair patch in 3D analysis.
The damaged fuselage skin modeled is 600 by 300 mm and 1mm thick, with a
center crack of about 55mm long. The skin material is Al 2024-T3. The
titanium repair patch is 155 by 155 mm2 andbolted onto the damaged structure skin (Figure 1). A typical
pressurized fuselage loading scenario is applied with 150MPa pressure
along peripheral direction and 50MPa in longitudinal direction. In this
case study, Titanium alloy was used for the repair patch material and
the patch is 1mm thick. Here, four cases are examined; among them three
crack treatments are considered in bolted patch repair:
- Un-repaired cracked structure where there is no crack
treatment is performed at all (fatigue crack propagation analysis is
conducted in BRSW)
- Live crack repair where patch bonded crack treatment
(Titanium patch) is performed (fatigue crack propagation analysis is
conducted in BRSW)
- Stop-drill crack repair where crack front is drilled w/
stop hole in addition to Titanium patch bonded repair (fatigue damage
analysis followed by crack propagation analysis in BRSW)
- Damage-removal crack repair where crack region is cut
out in addition to Titanium patch bonded repair (fatigue damage
analysis followed by crack propagation analysis in BRSW)
For comparison, the fatigue crack growth and service life estimation on
cracked skin for the un-repaired case is first analyzed as a reference.
A thru-the-thickness crack of size 53.4mm is initially inserted on the
wing structure, as shown in Figure 6a. Figure 6b shows the fatigue crack
growth of 5.3mm after 1027 service cycles, Figure 6c shows the crack
growth of 49.1mm, reaching a total crack length of 102.5mm after 4064
service cycles where it is considered structural failure [20] and
the skin to be replaced. Figure 6d shows the service life estimation in
the relationship between fatigue crack growth and continued loading
cycles. It is evident that BRSW FEA process is able to predict the
fatigue crack growing direction deviating from its initial pre-crack
orientation, driven by the practical service loading.