Damage mechanics
Fatigue lifetime
2mp )(1mdN/dD
FEA and Fatigue
damage calculation.
Geometry
Material property
Damage evolution law
Mean load change – Prediction models
Linear Cycle Mix (LCM) effect
)L/L(Lmn mnmaxmax)LLCM
•Two constants need to be defined
•Constants change with the type of load spectrum
N [cycles to failure]
Resid
ual lo
ad
‘R
’ [k
N]
Fatigue load decreasing
ab
cd
e
No interaction effect considered
Interaction effect considered
LCMRR bc
Complex loading
Vertical jump approach
•Independent of type of load spectrum
•No constants need to be defined
•Can be applied to any type of interaction effects
N [cycles to failure]
Resid
ual lo
ad
‘R
’ [k
N]
Fatigue load decreasing
a
b
cd
No interaction effect considered
Interaction effect considered
Complex loading
Variable amplitude fatigue
Type of load interaction
Experimental results (No. of cycles)
Miner rule prediction (No. of cycles)
LCM approach (No. of cycles)
Vertical jump approach (No. of cycles)
L1 = 6.5kN; L2 = 8kNn1=10; n2=5
1706 5020 1850 1707
L1 = 6.5kN; L2 = 8kNn1=1000; n2=5 18085 32127 21174 17757
L1 = 8kN; L2 = 9.5kNn1=10; n2=5
976 845 1869 1022
L1 = 8kN; L2 = 6.5kNn1 = 10; n2=5
12966 2704 19925 9518
Results and discussion
AC DC against CAA surface pre-treatment
Static strength
Cycles to failure for max. fatigue load of 60% of static strength
0
2
4
6
8
10
12
14
0 500 1000 1500
Conditioning [ no. of hours]
Stat
ic s
tren
gth
[kN
] v
AC DC
CAA
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
0 500 1000
Cyc
les
to f
ailu
rev
Conditioning [ no. of hours]
CAA
AC DC
ACDC Summary
A two-stage anodisation process has been developed to facilitate interphase formation without compromising corrosion protection.
The process is simple, fast and robust.
Initial results show excellent adhesion and corrosion performance – comparable to CAA.
4. CONCLUDING REMARKS
Given an understanding of film formation mechanisms oxides can be nanoengineered for optimised adhesion.
Hexavalent chromium chemistry is widely used in Al processing within the aerospace, defence, automotive sectors. Drop-in replacements are urgently sought.
ACDC processes offer additional advantages:environmentally benign
simpleincreased processing
speeds.
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