faa-drexel fellowship research program on crashworthiness third triennial international fire &...

FAA-Drexel Fellowship Research Program on

Crashworthiness

Third Triennial International Fire & Cabin Safety Research Conference, October 25, 2001, Atlantic City, NJ 1

Finite Element Simulation of a Vertical Drop Test

of a Boeing 737 Fuselage Section

A. Byar, J. Awerbuch, A. Lau and T. Tan

Drexel UniversityDepartment of Mechanical Engineering and Mechanics

Philadelphia, Pennsylvania

Presented atThird Triennial International Fire & Cabin Safety Research

Conference, October 22-25, 2001, Atlantic City, NJ


Crashworthiness


Acknowledgement

This work is sponsored by the FAA William J. Hughes Technical Center under Grant No.99-P-0056, and is part of the FAA-Drexel Fellowship Research Program.Gary Frings and Tong Vu are the program monitors.


Crashworthiness


Outline of the Presentation•Objectives•Drop Test of B737 Fuselage Section•Finite Element Model and Simulation•Results

• Deformation Time Histories of Frames• Acceleration Time Histories of Frames, Seat

Tracks, and Overhead Bins.• Load Time Histories of the Supporting

Structures of the Overhead Stowage Bins

•Conclusions and Summary


Crashworthiness


• Develop a finite element model and conduct a dynamic simulation of the drop test of a Boeing 737 fuselage section.

Objectives

• Refine the finite element model through a comparison of the simulation and experimental results.

• Develop a finite element based methodology to provide guidance for future testing conditions or configurations, and to simulate drop tests of other airframes that may be of interest in the future.


Crashworthiness


Performed in November 2000 at the FAA William J. Hughes Technical Center

Drop Test of the B737 Fuselage SectionWith Two Overhead Bins

• Ten foot long B737 fuselage section• Seven frames, from FS 380 to FS 500• A cargo door on the right-hand side• Two different overhead stowage bins• 18 seats with dummy passengers• Luggage stowed in the overhead bins

and the luggage compartment• Fully instrumented with strain gages

and accelerometers• 30 ft/sec initial impact velocity


Crashworthiness


Front View Back View

Hitco Bin Heath Tecna Bin

Drop Test of the B737 Fuselage Section


Crashworthiness


Drop Test of the B737 Fuselage Section


Crashworthiness


RightLeft

Forward

CargoDoor

Heath Tecna BinHitco Bin

Under-Floor Beams

Extra Under-Floor Beams

Camera Mounts

Finite Element Model


Crashworthiness


Cargo Door

Heath Tecna Bin

Camera Mount

SeatTracks

FloorLeft

Right

Forward

Aft



Crashworthiness


FS

50

0

FS

48

0

FS

46

0

FS

38

0

FS

40

0

FS

42

0

FS

44

0

Cargo Doorframe

FrameReinforcement

ReinforcementShort Beams

FS

50

0

FS

48

0

FS

46

0

FS

38

0

FS

40

0

FS

42

0

FS

44

0


Forward

Heath Tecna BinHitco Bin

Camera Mounts


Crashworthiness


Hitco Bin

FS 420

FS 400FS 460FS 480

• Bin is modeled with shell elements

• All supporting members are modeled with beam elements

Finite Element ModelCylindrical

Rod

VerticalTie Rod

VerticalLink

HorizontalLink

Short Beam


Crashworthiness


Heath Tecna Bin

FS 400

FS 420

FS 480

• Bin and C Channels are modeled with shell elements

• All other supporting members are modeled with beam elements

FS 460


Strut

C Channel

LongitudinalChannel

L Bracket


Crashworthiness


Finite Element Model57,589 Nodes, 56,652 Shell Elements, 67 Beam Elements.

Masses of luggage in the luggage compartment are distributed onto the lower frames.

Masses of seats and passengers are lumped to the seat tracks.

Masses of luggage in

overhead bins aredistributed in the bins

Masses of cameras are distributed on

the mounts


Crashworthiness


Material Initial Stiffness

(106 psi)

Final Stiffness

(106 psi)

Yield Stress

(103 psi)

2024-T3 10.3 0.61 28.0

7075-T6 10.3 0.65 72.0

Finite Element Analysis• LS-DYNA Explicit Code Used• Reduced-Integration Scheme Used for Shell Elements• Time Steps: Initial t = 410-6 sec., Final t = 110-6 • 30 ft/sec Initial Velocity, 0.350 sec. response calculated• Fuselage Skin: 2024-T3 Aluminum• All Other Structural Members: 7075-T6 Aluminum• Bi-Linear Stress-Strain Laws Used


Crashworthiness


Time (sec)

0.00 0.02 0.04 0.06 0.08 0.10

En

erg

y (1

06 in-l

b)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

Total EnergyKinetic EnergyInternal Energy

Impact Energy ConversionElasticResponse

95% of impact energy converted to internal energy


Crashworthiness


Time (sec)

0.00 0.02 0.04 0.06 0.08 0.10

En

erg

y (1

06 in-l

b)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

Total Internal EnergyFrames Lower Skin PanelsUnder-floor Beams Cargo Door Luggage

Energy Absorption

60% of totalinternal energy absorbed by frames


Crashworthiness


Deformation Time History of Frames

With Contour of Effective Plastic Strain

Results


Crashworthiness


Plastic deformation at the bottom of the frames

Flanges of the bottom frames show plastic deformation

Deformation Time History of Frames with Contour of Effective Plastic Strain


Crashworthiness


Plastic deformation at lower left & right corners

Buckling of flanges at the lower left & right corners



Crashworthiness


Flanges buckled

Aft doorframe has very little deformation



Crashworthiness



Plastic deformation

Plastic hinges formed

Kinks formed in the LHS frames

Plastic deformation in frames near the bin outboard supports

Fuselage section tilts to the leftEnergy mostly absorbed by the plastic hingesLittle deformation occurs in the upper portion


Crashworthiness


Plastic hinges hit the ground, set off a 2nd impact, primarily affecting LHS


Stiff aft doorframe causes RHS to deform more gradually

Plastic deformation caused by camera mounts

Beam/Frame Joints

Upper doorframe between FS 460 and FS 480 subject

to high shear force


Crashworthiness




Crashworthiness



Plastic deformation mostly occurs in lower frame

High shear force exerted by aft doorframe on

upper doorframe

Little deformation occurs in aft doorframe

No plastic deformation in frame reinforcement above the doorframe

Load transmit to upper frame differently through front and aft doorframes

Lower left corner crushed

Lower right corner deforms much less


Crashworthiness


Simulation at 100 ms

Deformation Time History

Actual Drop Test


Crashworthiness


Acceleration Time History - Frames

Results


Crashworthiness



Time (sec)

0.00 0.02 0.04 0.06 0.08 0.10

Z -

Acc

ele

ratio

n (G

)

-40

-20

0

20

40

60

80

100FS 380FS 400FS 420FS 440FS 460FS 480FS 500

RHS Frames

Time (sec)

0.00 0.02 0.04 0.06 0.08 0.10

Z -

Acc

ele

ratio

n (G

)

-40

-20

0

20

40

60

80

100FS 380FS 400FS 420FS 440FS 460FS 480FS 500

LHS Frames

Aavg=43.5Aavg=58.0


Crashworthiness


Frame Acceleartion - 200 ms

Time (sec)

0.00 0.05 0.10 0.15 0.20

Z -

Acc

ele

ratio

n (G

)

-40

-20

0

20

40

60

FS 400 RHS FS 400 LHS


LHS first peak value slightly higher

Plastic hinges delay the 2nd peak of LHS

2nd impact set off by LHS plastic hinges hitting the ground results in high acceleration on LHS

Elastic response after 100 ms


Crashworthiness


Acceleration Time History – Seat Tracks


Crashworthiness


Time (sec)

0.00 0.02 0.04 0.06 0.08 0.10

Z -

Acc

ele

ratio

n (G

)

-60

-40

-20

0

20

40

60

FS 380FS 400FS 420FS 440FS 460FS 480FS 500

RHS Inside Seat Track

Time (sec)

0.00 0.02 0.04 0.06 0.08 0.10

Z -

Acc

ele

ratio

n (G

)

-60

-40

-20

0

20

40

60

FS 380FS 400FS 420FS 440FS 460FS 480FS 500

LHS Inside Seat Track

Time (sec)

0.00 0.02 0.04 0.06 0.08 0.10

Z -

Acc

ele

ratio

n (G

)

-60

-40

-20

0

20

40

60

FS 380FS 400FS 420FS 440FS 460FS 480FS 500

LHS Outside Seat Track

Time (sec)

0.00 0.02 0.04 0.06 0.08 0.10

Z -

Acc

ele

ratio

n (G

)

-60

-40

-20

0

20

40

60

FS 380FS 400FS 420FS 440FS 460FS 480FS 500

RHS Outside Seat Track

Acceleration Time History – Seat Tracks

Aavg=13.6

Aavg=16.0 Aavg=16.6

Aavg=20.2


Crashworthiness


Acceleration Time History - Bins

Accelerations calculated at the forward end,the aft end, and the c.g. of each bin.



Crashworthiness


Acceleration Time History - Bins

Time (sec)

0.00 0.02 0.04 0.06 0.08 0.10

Z -

Acc

eler

atio

n (G

)

-10

-5

0

5

10

15

20

25Aft EndForward EndC.G.

Heath Tecna Bin

Time (sec)

0.00 0.02 0.04 0.06 0.08 0.10

Z -

Acc

ele

ratio

n (G

)

-10

-5

0

5

10

15

20

25Aft EndForward EndC. G.

Hitco Bin


First peak accelerationsRange: 14.5 G to 15.5 GAverage = 15.0 G

First peak accelerationsRange: 9.7 G to 20.0 GAverage = 15.0 G


Crashworthiness


Load Time History - Bins


Primary vertical supporting structure

Tie Rods Struts

Secondary (outboard) supporting members.

Vertical and Horizontal Links

L Brackets


Crashworthiness


Hitco Bin

Time (sec)

0.00 0.02 0.04 0.06 0.08 0.10

Fo

rce

(lb

)

-2000

-1000

0

1000

2000

3000

Forward Tie Rod Aft Tie Rod


Time (sec)

0.00 0.02 0.04 0.06 0.08 0.10

For

ce (

lb)

-2000

-1000

0

1000

2000

3000

Forward StrutAft Strut

Heath Tecna Bin

Load Time History – BinsPrimary Supporting Structures


Crashworthiness


Hitco Bin

Time (sec)

0.00 0.02 0.04 0.06 0.08 0.10

For

ce (

lb)

-2000

0

2000

4000

6000

Total Force in Tie RodsTotal Force in Vertical LinksTotal Vertical Force

Load DistributionPrimary vs. Secondary Supporting Structures


Crashworthiness


Load Distribution – Hitco Bin

Hitco Bin

Time (sec)

0.01 0.02 0.03 0.04 0.05

Rat

io

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Tie Rod Force / Total Vertical ForceNormalized Total Vertical Force

50% 100%


Crashworthiness


Load Distribution – Heath Tecna Bin

Heath Tecna Bin

Time (sec)

0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040

Rat

io

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Strut Force / Total Vertical ForceNormalized Total Vertical Force

50% 100%


Crashworthiness


Effect of Camera Mounts

Hitco Bin

Time (sec)

0.00 0.02 0.04 0.06 0.08 0.10

For

ce (

lb)

-3000

-2000

-1000

0

1000

2000

3000

Fwd Tie Rod with MountAft Tie Rod with MountFwd Tie Rod without MountAft Tie Rod without Mount


Crashworthiness


Conclusions• Finite element prediction of the deformed fuselage configuration

compared very well with that of the drop test.

• 95% of the impact energy converted to internal energy at approximately 90 ms.

• 60% of the internal energy is absorbed by the frames.

• The stiff cargo doorframe on the right-hand side causes the fuselage to deform in an unsymmetrical manner and has a significant effect on both the overall response of the fuselage section and components such as overhead bins.

• Under the current test condition the primary supporting members of Hitco bin (tie rods) carry approximately 55% of the total vertical load. Those of Heath Tecna bin (struts) carry approximately 75% of the total vertical load.

• Cameras and camera mounts cause substantial plastic deformation in the frames, and have some effects on the responses of overhead bins.


Crashworthiness


• A finite element model has been developed to simulate the drop test of a B737 fuselage section. Preliminary results, in terms of the deformed configurations, compared very well with those of the drop test.

• The finite element model will be further refined as the experimental data become available for comparison - work is underway.

• Frames mesh needs to be refined• Luggage needs to be modeled more realistically for energy absorption.• Other issues include employing more accurate material laws, better

damping models, failure criteria, etc.• Overhead bin certification can be greatly enhanced through a series of

parametric studies using the finite element model.• Knowledge gained in this work can be used to develop a finite element

based methodology to provide guidance for future testing conditions or configurations, and to simulate drop tests of other airframes that may be of interest in the future.

Summary and Future Work

faa-drexel fellowship research program on crashworthiness third triennial international fire &...

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