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ECERTA meeting, The University of Liverpool, 13th-15th September 2010
Stochastic Finite ElementStochastic Finite Element Model Updating and its
Application in AeroelasticityApplication in Aeroelasticity
Hamed Haddad Khodaparast
13 September 2010p
E C E R T A – E n a b l i n g C e r t i f i c a t i o n b y A n a l y s i s
Marie CurieExcellence Team
Contents
• Structural uncertainty in aircrafts
U i d lli i d id ifi i• Uncertainty modelling, propagation and identifications
• Application of forward propagation methods in Aeroelasticity
• Forward propagation results, Goland wing
• Uncertainty identification/stochastic model updating
• Probabilistic perturbation methodProbabilistic perturbation method
• Experimental validation of the perturbation method
• Interval model updating
N i l d i t l lt f i t l d l d ti
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
• Numerical and experimental results for interval model updating
Dowell, AFRL workshop, 2006Brooks et al, IFASD07
Tip attachment bolts - LCO
Structural uncertainty in aircrafts
Thomas, AIAA-2005-1917Tip attachment bolts LCO
Fuselage fuel mass – M =0.05
Pitt, AIAA-2008-2198
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
GVT: frequency variation 15%
Uncertainty modelling and propagation
Probabilistic models
AeroelasticAeroelastic system
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Uncertainty modelling and propagation
Non-Probabilistic models
Interval modelFuzzy sets
Propagation by 4 α level, for a function of two triangular fuzzy parameters.[D. Mones and D. Vandepitte JSV 288 (2005) 431-462]
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Uncertainty Propagation method
• Monte Carlo Simulation
• Perturbation methods
• Asymptotic integral
• Fuzzy‐logic
• Interval analysis
• Meta model
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Probabilistic model updatingp g
• The updating parameters are considered as random variables having presumed probability density functionspresumed probability density functions.
• The statistical moments of updating parameters will be updated so that p g p pthe scatter of measured data converges upon the scatter of analytical output data obtained from a randomised FE model.
Interval model updating• The updating parameters are defined to vary within an initial interval• The updating parameters are defined to vary within an initial interval.
• The interval of updating parameters will be updated using the scatter of measured data.
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Probabilistic model updating: p gperturbation method
)(1 jmjjj zzTθθ
M t
Classical model updating:
jjj zzz mmm zzz Measurement:
Prediction: Mean jjj
Variability
Parameters: θθθ n T
Transformation matrix: jΔTTT
Stochastic model updating:
n
kmk
mk
jj
1z
zT
ΔT
p g
jjmmjjjjjj ΔzzΔzzΔTTΔθθΔθθ 11
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Perturbation methodPerturbation method
jmjjj zzTθθΔO 1 :0
‐ the mean values of the updating parameters
jm
n
kmk
k
jjmjjj z
zzz
TΔzΔzTΔθΔθ)O(Δ 1
1
1 Δ:
k mkz1
‐ leads to an expression for the parameter covariances
Haddad Khodaparast, H, Mottershead, J.E., Friswell M. I., Perturbation methods for the estimation of parameter variability in stochastic model updating, Mechanical System and Signal
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Processing 22 (8) (2008) 1751‐1773.
Parameter covariances
jmjmjjjmjmjjjj ΔzΔzTΔzAΔθΔzΔzTΔzAΔθΔθΔθ ,Cov,Cov 11
Tjjj
Tjmj
Tjmjjj
jmjmjjjmjmjjjj
TΔzΔθTΔzΔθAΔzΔθΔθΔθ
ΔzΔzTΔzAΔθΔzΔzTΔzAΔθΔθΔθ
,Cov,Cov,Cov,Cov
,Cov,Cov 11
T
jjmjTjmmj
TTjmmj
TTjmj
Tjjmj
Tjmmj
Tjmmj
TTjmj
TΔzΔzTTΔzΔzTTΔzΔzATΔzΔθ
TΔzΔzATΔzΔzAAΔzΔzAAΔzΔθ
,Cov,Cov,Cov,Cov
,Cov,Cov,Cov,Cov
Tjjjj
TTjjmj
TTjjmj
TTjjj TΔzΔzTTΔzΔzTTΔzΔzATΔzΔθ ,Cov,Cov,Cov,Cov
jm
mn
jjm
m
jjm
m
j
zzzzz
Tzz
Tzz
TA
21 1
121 WSWSWSΤ Τ
jjΤjj
Cov(j,zj)and Cov(zj,zj) are determined by forward propagation
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Experimental Case Study – Plate Thickness Variability
Arrangement of accelerometers (A B C D) and driving point (F)Arrangement of accelerometers (A, B, C, D) and driving point (F)
4
5
ons
1
2
3
Num
ber
of o
bser
vatio
03.60-3.75 3.75-3.90 3.90-4.05 4.05-4.20 4.20-4.35
Thicknesses (mm)
Plate thickness distribution
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Model Parameterization
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Errors % of initial and updated standard deviation of parameters
500
400
500
300
%
200
Erro
r %
0
100
std (t1) std (t2) std (t3) std (t4)-100
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Interval model updatingCase2: updating parameters are geometric and output data are considered to be a vector including eigenvalues and eigenvectors of dynamic system. It can be mathematically shown that the parameter vertex solution is not valid inbe mathematically shown that the parameter vertex solution is not valid in this case.
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
An iterative procedure can be defined as follows for the solution of above equation:
jj
TTTj θθθθ θgΛρHμHθfADCBHHθ
11
To treat the ill‐conditioning of above system, a weighting function can be added to both side of above equation as:
j
Tj θθθWADCBHHθ
1
1
j
TTθθθθWθgΛρHμHθf
is chosen so that the condition number of whole matrix improvesθW
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
=1
=4
=1 =13 DOFClose modes
=4
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Optimal sampling in three dimensional problem p p g p
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Updated output parameters
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Experimental Case Study – Frame structure
Detailed FE model
Haddad Khodaparast, H, Mottershead, J.E., Badcock K.J., Interval Model Updating with Irreducible Uncertainty Using the Kriging Predictor, Mechanical System and Signal Processing
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
under review.
Measured and FE predictions of natural frequencies
Frame - Free Free
Mode No EXP FE err %
Clamped- Case 1Mode Exp. Hz FE Hz Error %
1 22 541 22 59 0 22Mode No. EXP. FE. err. %1 69.3 70.94 2.372 79.5 80.27 0.973 93 2 92 07 -1 21
1 22.541 22.59 0.222 27.844 27.27 -2.043 47.628 48.14 1.084 81 191 80 89 0 373 93.2 92.07 1.21
4 199.1 200.58 0.745 235.6 236.17 0.246 259 8 259 33 -0.18
4 81.191 80.89 -0.375 201.35 201.55 0.106 233.708 233.41 -0.137 256 398 259 05 1 036 259.8 259.33 0.18
7 286.3 288.73 0.858 297.1 296.4 -0.249 299 1 303 03 1.31
7 256.398 259.05 1.038 257.68 256.54 -0.449 283.094 283.35 0.09
10 298 46 305 34 2 30
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
9 299.1 303.03 1.3110 318.6 327.58 2.82
10 298.46 305.34 2.3011 312.387 316.49 1.31
Deterministic model updating of beam locations
True parameters Initial parameters Updated parameters Initial error % Updated error %θ1 θ2 θ1 θ2 θ1 θ2 θ1 θ2 θ1 θ21.0 1.0 1.6 1.6 1.04 1.02 60.00 60.00 3.73 2.001.0 2.0 1.6 2.4 1.00 2.15 60.00 20.00 -0.21 7.561.0 3.0 1.6 2.4 1.00 3.08 60.00 -20.00 0.20 2.762.0 1.0 1.6 1.6 2.04 0.90 -20.00 60.00 1.81 -9.782 0 2 0 2 4 2 4 2 13 2 00 20 00 20 00 6 48 -0 122.0 2.0 2.4 2.4 2.13 2.00 20.00 20.00 6.48 0.122.0 3.0 2.4 2.4 1.95 3.09 20.00 -20.00 -2.36 3.063.0 1.0 2.4 1.6 2.98 0.89 -20.00 60.00 -0.58 -11.003.0 2.0 2.4 1.6 2.99 1.83 -20.00 -20.00 -0.31 -8.363 0 3 0 2 4 2 4 2 93 2 98 -20 00 -20 00 -2 18 -0 583.0 3.0 2.4 2.4 2.93 2.98 -20.00 -20.00 -2.18 -0.58
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Initial and updated spaces of predicted data (100,000 points) based upon 9 measurement samples
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Initial and updated spaces of predicted data (100,000 points) based upon 9 measurement samples
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Initial and updated spaces of predicted data (100,000 points) based upon 9 measurement samples
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Application of forward propagation methods in Aroelasticity
0uAu ˆ
mmm
The aeroelastic responses can be estimated using following meta model within the region of variation of uncertain parameters:
Bθθθbθ TT
ji
m
jjiij
m
iiii
m
iii θθθθy 0
21
2
10
Twhere:
Tm ...21b
m
2...
2112
11
m
..2
...
222
22
BRegression coefficients
mm
sym..... Bθbθg 2
BθG 2
Gradient vector
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
θθθ BθG 2 Hessian matrix
Goland Wingg
1.72 Hz 3.05 Hz
Thicknesses of skins11.10 Hz9.18 Hz
Thicknesses of skins
Thicknesses of spars Thicknesses of ribs
Area of spar caps Area of rib caps Area of posts
ECERTA meeting, The University of Liverpool, 13th – 15th September 201026
Sensitivity Analysisy y
7 Structural parameters significantly influence flutter – vector
ECERTA meeting, The University of Liverpool, 13th – 15th September 201027
Results : Interval and MCSResults : Interval and MCS
Haddad Khodaparast, H, Mottershead, J.E., Badcock K.J., Propagation of Structural Uncertainty to Linear Aeroelastic Stability. Computers and Structures Volume 88, Issues 3-4, February 2010, Pages 223-236.
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Pages 223 236.
Results: Interval Analysisy
Interval flutter speed
Interval analysis – COV=0.05
420
440Interval flutter speed
Upper boundLower boundMC samples
400
ft/s)
360
380
tter s
peed
(f
340
flut
0.65 0.7 0.75 0.8 0.85 0.9 0.95 1300
320
M h b
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Mach numbers
Results: Probabilistic and Fuzzy
- Aeroelastic problem using linear aerodynamics
Meta model (Response Surface method) can be used to evaluate gradient and Hessian matrix and to gspeed up the procedure
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
198 Degrees of Freedom
Correlation Coefficient: Crossing Modes
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Correlation Coefficient: Crossing Modes
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Propagation of structural damping to Aeroelastic analysisPropagation of structural damping to Aeroelastic analysis
Dr Marco Prandina
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Dr Marco Prandina
Current and future work
GARTEUR SM‐AG19
Application of forward propagation methods in LCO problem
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
Conclusions• Different forward propagation methods have applied to the problem of flutterDifferent forward propagation methods have applied to the problem of flutter
analysis in aeroelastic system.
• Interval analysis (with Response‐Surface optimisation) was found to be efficient and produces enough information about uncertain aeroelastic system responses.y p
• The flutter boundary becomes increasingly sensitive to structural variability, as the stability threshold is approached.
• Efficent perturbation methods have been developed for identification of the ranges of input varitaion from measured output variations.g p p
• Interval model updating has developed and it is shown that the method is bl f d i i l i h f llcapable of producing quite accurate results even in the presence of small
number of measured data.
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010
• The stochastic updating methods are verified experimentally.
AcknowledgementAcknowledgement
This research is funded by the European Union for the Marie Curie Excellence Team ECERTA
under contract number MEXT‐CT‐2006‐042383
Thanks for your attention !
ECERTA meeting, The University of Liverpool, 13th – 15th September 2010