Bird Strike Methodology.pdf

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- Southwest Portland Flight Has Bird Strike Incident

January 1, 2012

- Iberia A340 Suffers Major Damage by Bird Strike

May 13, 2012

- Bird Strike Hits US Airways 757 at Orlando, Damages Radome

May 14, 2012

-

AirTran 717 Jet Returns to Orlando Due to Bird StrikeJuly 25, 2012

- United 757 Jet Suffers Bird Strike While Landing at Portland

November 20, 2012

http://airnation.net/

Bird Strike Incidents Few From Many

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Figure 2: Damage


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-

Bird strike accidents are common and dangerous in the Aerospaceindustry

- Over 250 passengers and crew have been killed since 1988

- Wild life strikes cost the US civil aviation industry $700 MN and

500,000 downtime hours every year

- FAA certification requires an aircraft to land safely after impact

About Bird Strikes

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Figure 1: Percentage of damage due to


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FAA Requirements

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29/01/2016 FAR COMPONENTS BIRD MASS AIRCRAFT SPEED SPECIFIC REQUIREM

25.571(e)(1) General Structure 4lb Vc @sea Level .85 Vc Successful completio

25.631 Empennage 8lb Continued safe flight

25.775 (b) Windshield 4lb Bird does not penetra

25.775 (c) Windshield No specified No specifiedMinimize danger to pi

windshield fragments

25.1323(j)Duplicate Pitot

TubesNo specified No specified Bird does not damage

29.631 General Structure 2.2 lbLesser of Vh or V Ne to

8000 ft

Continued safe flight

(Category A) Safe Lan

25.775(h)(1) Wind Shield 2 lbMaximum flap

approach speedBird does not penetra

23.1323(f) Duplicate pitot tube Bird does not damage


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-

Aircraft engines and structures are tested by firing dead chickensfrom a cannon at varying weights and speeds

- These tests require a lot of planning and cost millions of dollars

- Which increases the product life cycle and cost

-Leads to killing of countless bird in the process of testing &

certification

- Reusability after damage

Bird Strike Testing

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Figure 3: Bird strike test


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- Increased computational capability in the recent advancements

in FEA facilities use of different simulations techniques with

better accuracy

- # of commercial software's and techniques are available in the

market

- High skilled engineers are required

- Accuracy varies from software to software from user to user

- FE modeling time is more (60-70% of total time)

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Figure 4: Computer based bird

Business problems: Bird Strike Simulation


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Right method for the right purpose

-Lagrangian method

- Coupled Eulerian Langrangian method (CEL)

- Smooth Particle Hydrodynamics (SPH)

Fastener/Riveted Joints Modeling

- # of joints

- Damage model for fastener under impact loads

-Accurate modeling of fasteners is time consuming / complex

- Micro level mass matching around fastener hole

FEM Setup time, run time and accuracy of pressure and deflection

Technology Challenges


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SafeBird : Solution Architecture

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SafeBird is a Intelligent platform which integrates Catia, Hyper mesh and LSDYNA/Abaqus for birds strike

Objective

The objective is to help and guide the user on to carry out bird strike analysis and to solve the same consideparameters

Figure 5: SafeBIrd Solution Architecture


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About SafeBirdTM

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Geometry

from CAD

Application Interface

Input

Multiple Iterations to

Optimize Simulator

Option to browse the CAD

step input file

Options to interact with HM

in batch/interactive mode &

execute the HM Processes

Options to interact with

Abacus/LSDyna in interactive

mode & execute the AbacusProcesses

Hyp

Pro

Meshing of Model

Mesh Quality checks

Fastener creations

Material assignment

Abac

Proc

Meshed model from HM

Apply BCs

Perform Checks

Solve Analysis

Reporting

Results

Output

Figure 6: SafeBird flow diagram


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Bird of mass 4 lbs is simulated

Bird material accounts 10% material porosity

Bird FEM idealized with

- Lagrangian solid element (C3D8R) Pure Lagrangian

-Particle element (PC3D) SPH

- Eulerian element (EC3D8R) CEL

Bird geometry idealized by a cylinder with hemispherical ends

Figure 7: Bird M

Analysis method


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- Nodes are associated to particle in the material

- Easy to track history dependent materials

- Bird mass is fixed

-

Decrease of time value causes convergence issues- Excessive distortion produce

Figure 8: Soft Body Impactor Modeling using P

Pure Lagrangian


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-Mesh remains fixed, material flows through the mesh

- Imactor fluid like body Eulerian element

- Target solid structure Lagrangian elements

- No stability problems

- Loss of bird mass

- Computational domain is large

- High computational cost

- Fine mesh for accurate results

Coupled Eulerian Lagrangian (CEL)

Figure9: : Soft Body Impact


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-Solid FE mesh is replaced by a set of discrete

interacting particles

- It has variable connectivity which allow severe

distortions

- Knowledge of interaction with the neighboring

particles is important- For neighboring search, bucket sort algorithm is

used

- Average number of particles associated with an

element is 30 50

Figure 10 : Soft Body Impactor Modeling u

Smooth Particle Hydrodynamics (SPH)


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Bird Strike occurs at relatively high

speeds

Flow of bird material lead tospreading the impact forces

When soft body impacts a target, acomplex pressure field is formed

Pressure time response shows 3distinctive stages

- Initial impact phase

- Shock propagation phase

- Steady flow phase

Pressure Variation- Soft Impact

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Figure 11: Press ure variation in a soft body impact


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Equation of State (EOS) Validation

- Validation is done by comparing the Hugoniot and

stagnation pressures developed

- At a velocity of 116 m/s and 225 m/s, Pure Langrangian,

CEL , SPH, theoretical and experimental values are

compared

Figure 12-a: Stagnation Pressure variatio

Figure 12-b: Hogoniot Pressure variatio


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PURE LANGRANGIAN CEL SPH

Advantages Time for FEM is less

Energy conservation and

computation time is less

Time for FEM is low

Actual behavior is simulated

Better accuracy and stability

Difficulties deformatio

resolved

ComputatioHigher accu

Disadvantages Less accurate, excessive

element distortion leading to

instability

Computation time is high

Accuracy at the cost of

computation time

Time for FE

Recommendation Preliminary checks for FEM

formulation

Best used where detailed fluid

response is required

When sever

expected

Comparison summary


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BSSI is calculated using the following parameters

-FEM setup time

- Run time

- Accuracy

BSSI is a holistic index, which helps the user to choosethe method to simulate bird strike analysis

ACCURACY FEM SETUP TIME RUN TIME

SPH 8 5 2

Pure Lagrangian 1 2 2

CEL 5 3 8

BSSI Bird Strike Simulation Index


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- In high velocity impact , fasteners will take both shear and tensile loads of high m

- Fasteners were defined with coupled behavior

- Fasteners play a critical role in deciding the probable failure location and the failu

- Fasteners are modelled as connector element type CON3D2 in ABAQUS

- The elastic properties of fastener material such as stiffness, fastener allowable a

modulus were taken from (MMPDS01, FAA)

-The connector elasticity behavior was assigned to connector

- The connector progressive damage behavior was assigned by defining force bas

initiation criteria and motion based damage evolution criteria available in ABAQU

Fastener Simulation


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Simulation Results

Fastener failure was observed in both methods at impact locations but failed to pre

structure failure which developed as crack propagation between riveted joints

Figure 13: Simulation results comparison


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- A finer mesh was modeled with the

intention of observing the crack

formation

- Fastener hole equivalent volume is

subtracted

-With a finer mesh, the penetration

observed is relatively greater than

coarser mesh

Alternate fastener damage model

Figure 14: Different FE mesh sizing


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Experimental vs Simulation

Figure 14: results comparison with published paper


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Damage of wing flap structure

Experimental vs Simulation


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- Bird strikes incidents are common and are great threat to the passengers and crew and r

significant damage to the aircraft

- FAA Mandates bird strike testing and that requires lot of planning , time and cost

- Computer simulations help to save cost, time and no of birds

- SafeBird is intelligent integrated platform to integrate cad, meshing and FE solver

- SafeBird save time and help less expertise user to perform bird strike analysis

- Data needs to feed continuously to SafebBird knowledge base

- Present methodology predicts results with 98% of accuracy.

Summary & Conclusions

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