Worst-case Gust Loads Analysis in the Presence of Non

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

Lucia Garcia Matas 22/11/2017 – DiPaRT Conference

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


Pilot Structure

Introduction

Predominant practice

New framework for

Investigation of the influence of structural non-linearities on worst-case gust loads

predictions

Lucia Garcia Matas

Aircraft design is limited to a linear and deterministic regime, in spite of rapidly increasing demands to

consider unavoidable non-linearity

22/11/2017 – DiPaRT Conference

Introduction

Lucia Garcia Matas

Worst-case gust loads

Linear aeroelastic model

Input parameters Dynamic gusts

IQs (shear force, bending moment, torque…)

Critical load values!


Introduction

Lucia Garcia Matas

Non-linearity

Sources


Previous work


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


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

Lucia Garcia Matas

DLM + RFA


GAF matrix related to generalized

coordinates

GAF matrix related to the

gust

Gust loads

Lucia Garcia Matas

Discrete 1-cos Gust


Kx,Ky,Kz,Krx,Kry,Krz

Non-linearity modelling


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


Mass

Gust length Speed Altitude

Mass modelling


Fuel tank

General Loads Process

Lucia Garcia Matas

Gust

Structural model Aerodynamic model

MPF


K M Modal Base

GAF RFA

GAF time

Post-process

Loads and Displacement

ODE

Results and analysis


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


-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


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


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


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?


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.

Documents

Worst-case Gust Loads Analysis in the Presence of Non