Worst-case Gust Loads Analysis in the Presence of Non ...
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Worst-case Gust Loads Analysis in the Presence of Non-linearity
Final MSc Dissertation
Lucia Garcia Matas
Academic supervisor: Hamed Haddad Khodaparast
Industrial supervisors: Simon Coggon, Andrea Castrichini
22nd November 2017
Contents
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o Introduction
o Previous Work
o 3-D Goland Wing Model
o Input parameters
o General loads process
o Results and analysis
o Conclusions
o Future work
Introduction
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Pilot Structure
Introduction
Predominant practice
New framework for
Investigation of the influence of structural non-linearities on worst-case gust loads
predictions
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Aircraft design is limited to a linear and deterministic regime, in spite of rapidly increasing demands to
consider unavoidable non-linearity
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Introduction
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Worst-case gust loads
Linear aeroelastic model
Input parameters Dynamic gusts
IQs (shear force, bending moment, torque…)
Critical load values!
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Introduction
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Non-linearity
Sources
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Previous work
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2-D gust model Generalized response vector
Aerodynamic response-dependent matrices
Non-linear restoring force function
Inertia matrix
Structural damping
matrix
Structural stiffness matrix
Vector of time-dependent wind gusts
3-D Goland Wing model
Lucia Garcia Matas 22/11/2017 – DiPaRT Conference
Generalized coordinates vector
Structural stiffness matrix
Aerodynamic forces
Non-linear restoring force function
Mass matrix Damping matrix
Kx,Ky,Kz,Krx,Kry,Krz
3-D Goland Wing model
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DLM + RFA
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GAF matrix related to generalized
coordinates
GAF matrix related to the
gust
Gust loads
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Discrete 1-cos Gust
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Kx,Ky,Kz,Krx,Kry,Krz
Non-linearity modelling
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Cubic non-linear spring with 6 components:
X,Y,Z,RX,RY,RZ
Spring force function
VEAS
Alt
itu
de
Gu
st v
elo
city
Time (s)
Input parameters
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Mass
Gust length Speed Altitude
Mass modelling
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Fuel tank
General Loads Process
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Gust
Structural model Aerodynamic model
MPF
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K M Modal Base
GAF RFA
GAF time
Post-process
Loads and Displacement
ODE
Results and analysis
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Linear: Kl= [108, 108, 1.4x104, 108, 5x105, 108]
Non-linear: Kl= [108, 108, 1.4x104, 108, 5x105, 108]
Kn=[ 0 , 0 , 1.4x104, 0 , 5x105, 0 ]
Units: Kx,Ky,Kz (Ibf/ft) Krx,Kry,Krz (Ibf*ft/rad)
-2 -1 0 1 2 3 4 5
104
-2
-1
0
1
2
3
4
510
5
-2 -1 0 1 2 3 4 5
105
-5
-4
-3
-2
-1
0
1
2
3
4
510
4
-2 -1 0 1 2 3 4 5
104
-5
-4
-3
-2
-1
0
1
2
3
4
510
4
Critical cases
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-2 -1 0 1 2 3 4 5
104
-5
-4
-3
-2
-1
0
1
2
3
4
510
4
Different critical cases!
Levels of non-linearity
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Weak non-linearity: Kl= [108, 108, 1.4x104, 108, 5x105, 108]
Kn=[ 0 , 0 , 1.4x102, 0 , 5x103, 0 ]
Strong non-linearity: Kl= [108, 108, 1.4x104, 108, 5x105, 108] Kn=[ 0 , 0 , 1.4x104, 0 , 5x105, 0 ]
-2 -1 0 1 2 3 4 5
104
-2
-1
0
1
2
3
4
510
5
Conclusions
Lucia Garcia Matas 22/11/2017 – DiPaRT Conference
The results from the previous two academic models show the impact of non-linearity in the critical gust load cases.
Critical cases for the linear model are considerably different from those of the non-linear models. At certain flight points, the critical loads become more extreme.
Future work
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Following step: To apply the approach to the full aircraft model. Main idea: To model the attachments of the pylons of the engines as cubic non-linear springs, as previously done in the Goland Wing model.
Thank you for your attention. Any questions?
Lucia Garcia Matas 22/11/2017 – DiPaRT Conference
Wright, J.R., and Cooper, J.E., “Introduction to Aircraft Aeroelasticity and Loads”, West Sussex, United Kingdom: John Wiley and Sons, Ltd., 2015. Khodaparast, H.H., Coggon, S., Friswell, M.I., and Cooper, J.E., "The Effects of Structural Nonlinearity on the Dynamic Response to Aeroelastic Gust Models", Conference: 27th International Conference on Noise and Vibration Engineering (ISMA 2016), 2016.