ap'i - dtic · project 2402, "vehicle equipment technology," task 240203,...

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RESEARCH INSTITUTE ' --------M

DAYTON, OHIO 45469

UechniVal ReSITY OF AY -_-80-3 ApR 4

< "A'pproe For public lelease isrbution unlimited.

=FLIGHT DYNAMICS LABORATORYAIR FORCE WRIGHT AERONAUTICAL LABORATORIES

AIR FORCE SYSTEMS COMMANDDAY WRIGHT-PATTERSON AI4 FORCE BASE, OHIO 45433

d3

S81 4 14 45

NOTICE

When Government drawings, specifications, or other data areused for any purpose other than in connection with a definitelyrelated Government procurement operation, the United StatesGovernment thereby incurs no responsibility nor any obligationwhatsoever; and the fact that the government may have formulated,furnished, or in any way supplied the said drawings, specifica-tions, or other data, is not to be regarded by implication orotherwise as in any manner licensing the holder or any otherperson or corporation, or conveying any rights or permission tomanufacture use, or sell any patented invention that may in anyway be related thereto.

This report has been reviewed by the Office of PublicAffairs (ASD/PA) and is releasable to the National TechnicalInformation Service (NTIS). At NTIS, it will be available tothe general public, including foreign nations.

This technical report has been reviewed and is approved forpublication.

ROBERT E. MCCARTY R. HAP.LEYWALKERProject Engineer Group Leader

Subsystems Development Group

* ~FOR THE CONMANDER

"A.MBROSE B. _NUTTDirectorVehicle Equipment Division

Copies of this report should not be returned unlessreturn is required by security considerations, contractualobligations, or notice on a specific document.

AIR FORCE/5G 780/25 March 19111 - 240

SECURITY CLASS- VICATION OF THI% 0'3E (I. Date.et•.oed

REPORT DOCUMENTATION PAGE RE r INSTRUCTIONSI EFEFOI CO.. _I _NG IFOR

is REPORT NUMOE .. GOVT ACCHSF.4N NO.3 PFC"- I.-T7. rA•C*G Nu(e

"AWAL-TR-80-3098 7______4. TITLE (ad Subte) S. T7FE 3; 1'LvOCl & PERIOD COVERLD

VALIDATION OF A BIRD SUBSTITUTE FOR FINAL TECHNICAL REPORTDEVELOPMENT AND QUALIFICATION OF JJULY_1979 - JULY 1980AIRCRAFT TRANSPARENCIES 1 6 PERFOhI..NG ORG. REPORT NUMURE

I-UDR-TR-80-697. AU THOR(*) CON'. RACT O9 GRANT NUMBER(s)

ANTONIOS CHALLITA ! F33615-78-C-3402

9. PER."ORMING ORGANIZATION NAME AND ADDRESS 1n -PCf- *-A FLEAIENT. PROJECT. TASK.4.:-A A WOH- "INIT NUMBERS

UNIVERSITY OF DAYTON RESEARCH INSTITUTE IPROG. ELE. 62201F300 COLLEGE PARK AVE. PROJ. 2402, TASK 240203DAYTON, OHIO 45469 - WORK .II 240 I

i7. CONTROLLING OFFICE NAME AND ADDRESS I1. REPORT DAI'

FLIGHT DYNAMICS LABORATORY (FI) OCTOBER 1980AF WRIGHT AERONAUTICAL LABORATORIES, AFSC '. NUIBEPn r PAGESWRIGHT-PATTERSON AIR FORCE BASE, OH 45433 76

14. MONITORING AGE,4CY NAME & ADORESS(If different (too Co•trollng Office) IS. SECURITY CLASS. (of tlAS ,porl)

UNCLASSIFIEDIS.. DECLASSIF;CATION DOWNGRAOING

SCHEDULE

16. DISTRIBUTION STATEMENT (of this Repwa)

Approved for public release; distribution unlimited.

I7. DISTRIBUTION STATEMENT (of the abottsc entered in Boack 20. It dilferont (tom Report)

IS. SUPPLEMENTARY NOTES

I9. KEY WORDS (Conlidue on reverse side It nocees7 ud Idelntl by block runmb.r)

Foreign object damage, bird substitute, transparencies, birdimpact, minimum perforation velocity, polycarbonate panels,impact loads.

20. ABSTRACT (Contnue an reveres•sde Id n.eceseur end IdentllO by block ib.r)

SThis report describes an experimental study designed to vali-date a substitute bird for development and qualification ofaircraft transparencies. For a substitute bird to be acceptedby the transparency community it has to generate the same impactloads as real birds and damage the transparency in the samemanner. Nominal 450 g real and spherical substitute birds werelaunched onto 0.635 cm thick polycarbonate panels at four,-,

DOI JAN 73 1473 EDITION OF I NOV SS IS OBSOLETE

SECURITY CLA .•*rIF&iw,.-• 4.S PACC ,'0.-., *l,.,

I l l I I I I I

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SECUMITY CLASSIFICATION OF THIS PAGO(E~di, DaI" -k--. ..

different locations. The minimum perforation velocity wasused as the main criterion to measure/,damage; however, per-foration wasn't achieved at the centýt panel and at the lower,or upstream, corner. There ore, o1er measures of damagewere adopted for these Joc tions;A/ength of cracks, depth ofpocket, etc. Also, tempo al and-spatial distribution of loadswere measured for 60 and 600 9 spherical substitute birds atthree impact angles (90Y, 45*, and 25*) and three velocities(100, 200, 300 m/s). Time-pressure traces recorded in thisprogram showed a rise and decay of a shock pressure; no steady-state flow was observed. A direct comparison of the damagepotential of real birds pherical substitute birds, and end-oncylinders (measured in a revious program where effects oforientation at impact were studied) shows that end-on cylindershave similar damage potenti 1 to real birds, and from previouswork reported by Challita et al in Reference 3 we know thatend-on cylinders generate sim lar impact loads to real birds;therefore, end-on cylinders we e selected as the substitutebirds to be used in development and qualification oftransparencies.

\I ,\I

\9

I

1

I

SIECURIiTY CLASSIFICATiON OF THiS PAGEU'When Date Eatecwd)

I

- FOREWORD

This report describes a contractual work effort conducted

by personnel of the Impact Physics Group within the Experimentaland Applied Mechanics Division at the University of DaytonResearch Institute for the Flight Dynamics Laboratory under

Project 2402, "Vehicle Equipment Technology," Task 240203,

"Aerospace Vehicle Recovery and Escape Subsystems," Work Unit

24020318, "Simulation of Bird Impact on Aircraft Transparencies."

The Project Monitor was Mr. Robert E. McCarty and Mr. George Rothwas the Project Supervisor for the University. Dr. John Barberand Mr. Blaine West contributed to planning the experiments.

This report is the last of three to be published underContract No. F33615-78-C-3402. The first two dealt with

scaling the impact loads and studying the effects of birdorientation at impact on damage level.

Accession For'rrs GRA&IJ'I C TAB

t ~U;-inunmeed f3•s I£cation.

rt

* .• .-* . •.• .-, o1•

¢..J- ,~II

Liii

TABLE OF CONTENTS

SECTION PAGE

I INTRODUCTION 1

II EXPERIMENTAL TECHNIQUES 5

III EXPERIMENTAL RESULTS 15

IV CONCLUSIONS AND DISCUSSION 38

V RECOMMENDATIONS 41 1APPENDIX A - PHOTOGRAPHS OF DAMAGED PANELS 42

APPENDIX B - BIRD SUBSTITUTE SPECIFICATIONS 61

REFERENCES 63

I

Li

'I

LIST OF ILLUSTRATIONS

FIGURE PAGE

1 Overall View of 177.8 mm Gun Range 6

2 Foam Plastic Sabots Used for LaunchingSpherical Birds 7

3 Overall View of the 88.9 mm Gun Range 8

4 Support Structure and Mounting Frame Usedwith the 88.9 mm Gun 10

5 Support Structure and Mounting Frame Usedwith the 177.8 mm Gun 11

6 X-radiograph of a Spherical Substitute Birdin Free Flight 12

7 Sections of Film Taken During the First ShotConducted with Spherical Bird Substitutes 13

8 Spherical Substitute Bird Cut into Four Piecesto Show its Homogeneity 16

9 Impact Locations of Real and Substitute Birdsonto Polycarbonate Panels 17

10 Projection of a 1-lb. Spherical Substitute Birdonto a Polycarbonate Panel at 250 Angle of Inci-dence when Impacting the Center Edge Location 30

11 Projection of a 1-lb. Cylindrical SubstituteBird with End-on Orientation onto a Polycarbon-ate Panel at 250 Angle of Incidence when Impact-ing the Center Edge Location 30}

12 Typical Pressure-Time Record of Nominal 600 gSpherical Substitute Bird (Gelatin with 10Percent Porosity). (a) 900 impact; centertransducer; 'b) 450 impact, 3" below center-(c) 250 impact, 2" below center 33

13 Typical Pressure-Time Record of Nominal 60 g

Spherical Substitute Bird (Gelatin with 10Percent Porosity). (a) 900 impact; centertransducer; (b) 450 impact; 2" below center;(c) 250 impact; 3" below center 34

v.IvI IIiI I I I I I

r

FIGURE PAGE

14 Comparison of Measured Peak Pressures toTheoretical Hugoniot for 60 and 600 gSpherical Substitute Bird at Normal Impact 36

15 Comparison of Measured Peak Pressures toTheoretical Hugoniot for 60 and 600 gSpherical Substitute Bird at 450 Impact 36

16 Comparison of Measured Peak Pressures toTheoretical liugoniot for 60 and 600 gSpherical Substitute Bird at 250 Impact 37 I

A-i Shot No. 5-0195; Panel Impacted at theCenter Edge; 1-lb Spherical Gelatin Launchedat 192 m/s. (a) front view; (b) end view 43

A-2 Shot No. 5-0196; Panel Impacted at the CenterEdge; 1-lb Spherical Gelatin Launched at188 m/s. (a) front view; (b) end view 44

A-3 Shot No. 5-0197; Panel Impacted at the CenterPanel; 1-lb Spherical Gelatin Launched at A30A4 m/s. (a) front view; (b) end view. 45

A-4 Shot No. 5-0199; Panel Impacted at the CenterPanel; 1-lb Spherical Gelatin Launched at320 m/s. (a) front view; (b) end view 46

A-5 Shot No. 5-0200; Panel Impacted at the CenterPanel; 1-lb Spherical Gelatin Launched atz>325 m/s. (a) front view; (b) end view 47

A-6 Shot No. 5-0203; Panel Impacted at the Down-stream Corner; 1-lb Spherical Gelatin Launchedat 179 m/s. (a) front view; (b) end view 48

A-7 Shot No. 5-0208; Panel Impacted at the Down-stream Corner; 1-lb Spherical Gelatin Launchedat 186 m/s. (a) front view; (b) end view 49

A-8 Shot No. 5-0210; Panel Impacted at the Up-stream Corner; 1-lb Spherical Gelatin Launchedat 305 m/s. (a) front view; (b) end view 50

A-9 Shot No. 5-0211; Panel Impacted at the Up-stream Corner; 1-lb Spherical Gelatin Launchedat 321 m/s. (a) front view; (b) end view 5.

A-10 Shot No. 4-0147; Panel Impacted at the CenterEdge; 1-lb Pigeon Launched at 213 m/s.(a) front view; (b) end view

vii

I4

FIGURE PAGE

A-I1 Shot No. 4-0150; Panel Impacted at the CenterEdge; 1-lb Pigeon Launched at 211 m/s. 5(a) front view; (b) end view

A-12 Shot No. 4-0156; Panel Impacted at the CenterPanel; 1-lb Pigeon Launched at 308 n/s.(a) front view; (b) end view 54

A-13 Shot No. 4-0157; Panel Impacted at the CenterPanel; 1-lb Pigeon Launched at 313 m/s.(a) front view; (b) end view 55

A-14 Shot No. 4-0158; Panel Impacted at the centerPanel; 1-lb Pigeon Launched at 294 m/s.(a) front view; (b) end view 56

A-15 Shot No. 4-0160; Panel Impacted at the Down-stream Corner; 1-lb Pigeon Launched at191 m/s. (a) front view; (b) end view 57

A-16 Shot No. 4-0162; Panel Impacted at the Down-stream Corner; 1-lb Pigeon Launched at193 m/s. (a) front view; (b) end view 58

A-17 Shot No. 4-0164; Panel Impacted at the Up-stream Corner; 1-lb Pigeon Launched at308 m/s. (a) front view; (b) end view 59

A-18 Shot No. 4-0165; Panel Impacted at the Up-stream Corner; 1-lb Pigeon Launched at306 m/s. (a) front view; (b) end view 60

viii

LIST OF UNIT'S

Mass g (gram) - 0.0022 Ibm (pounds-mass)

kg (kilogram) i 0 3 g

Length m (meter) = 3.2808 ft (feet)

- 39,37 in (inches)

cm (centimeter) - 0.01 AlS 0.39.7 in

mm (millimeter) = 0.001 m

Time s (second)

liS (microsecond) = 10- 6 s

Force N (Newton) U 0.2248 lbf (pounds-force)

MN (Meganewton) = 106 N

3 ~3Density kg/r3 0.0624 Ibm/ft3- 3. 6.13 x 105 lbmn/in3'

Pressure MN/m 2 = 10 bars2

- 145.04 lbf/in

Frequency IiZ (hertz) 3

kHz (kilohertz) = 0 Hz

ix

LIST OF SYMBOLS

D Diameter of the bird

ID Inside diameter

L Length of the bird

OD Outside diameter

P,Pp PMeasured peak pressure

PH lHugoniot pressure

t Time

V Impact velocity

V n Normal component of impact velocity

V• Shock velocity

Density of projectile

0 Angle o' impact

x

Ih.. 1 _

SECTION IINTRODUCTION

Birds and aircraft occupy the same air space and collisions

between the two are inevitable. As a result of the increasingnumber of catastrophic bird-aircraft collisions, the UnitedStates Air Force has initiated a number of programs with the

objective of developing and applying the technology required to

protect aircraft against birdstrike. Some of these programs havedealt with characterization of the loads generated during a bird-

strike and with the testing procedure used to evaluate the level of

birdstrike protection afforded by a given flight hardware system.

A strong random variation was found in the bird impact

loads data collected during the early stages of the bird impactstudies. These variations were apparently due to inherent

variability in material properties, structures, and geometryof birds. This fact raised serious questions about the conduct

of test programs using real birds to screen candidate Lrans-parency designs. It was therefore desirable to develop andvalidate a suitable substitute bird which has much more repeat-

able impact loads and will contribute significantly to theclear interpretation of such test results. This report deals

with the validation of such a substitute bird.

1. 13ACXGROUND

Early investiqations of bird impact loading conducted

at the Air Force Materials Laboratory and the University

of Dayton Research Institute identiried a number of

deficiencies in the use of real birds as a testing medium.

These were attributed to the inhomogeneity of real birds and

the irregular geometry of the bird carcass. Thus, the use of

real birds in development and qualification testing introduces

unknown and uncontrollable experimental variables. In addition,

it is often desirable to perform subscale laboratory tests

1

during development of transparency components rather than full-

scale component tests. Since birds are not available in a

variety of well defined and controlled sizes, subscale laboratory

testing with real birds is often impossible. An easily fabri-cated and scaleable substitute bird is essential for laboratory

subscale testing. It was, therefore, desirable to develop and

validate a suitable substitute bird for use in transparencyi• impact testing.

For a substitute bird to be accepted for development and

qualification testing of transparencies, it is necessary to

demonstrate that the substitute bird generates substantially

the same loads as a real bird during impact; and that it does

the same damage to a transparency as a real bird. If the sub-

stitute bird has the same material properties and geometry as

a real bird, it will generate the same impact loads. The

theoretical work reported by Wilbeck in Reference 1 demon-

strated that a good material substitute for birds is gelatin

with 10 to 15 percent porosity. This material was molded as

right circular cylinders and was extensively tested in the first

and second phase of this contractual effort, and was found

to generate the same impact loads as real birds when launched

with end-on orientation. This work was reported by Challita

in References 2 and 3.

The geometry and orientation at impact of the bird are

two important factors which should be considered while develop-

ing and validating a substitute bird. The pressure data

collected at AEDC and reported by Barber in Reference 4 showed

1. Wilbeck, J.S., "Impact Behavior of Low Strength Projectiles,"AFML-TR-77-134, July 1978.

2. Challita, A. and B.S. West, "Effects of Bird Orientation atImpact on Load Profile and Damage Level," ArWAL-TR-80-3009,June 1980.

3. Challita, A. and J.P. Barber, "The Scaling of Bird ImpactLoads," AFFDL-TR-79-3042, June 1979.

4. Barber, J.P., J.S. Wilbeck, and H.R. Taylor, "Bird ImpactForces and Pressures on Rigid and Compliant Targets,"AFFDL-TR-77-60, May 1978.

2

pronounced effects of orientation on bird impact pressures.

Therefore, a test program was conducted where cylindricalgelatin birds were launched with controlled orientation and

the effects of orientation at impact were studied and theworst-case orientation was identified and recommended to be

used in subsequent design and proof testing of aircraft trans-parencies. This work was reported by Challita in Reference 2.

The geometry of a real bird is approximately an oblatespheroid. Most substitute birds currently used are right cir-cular cylinders, and for many testing circumstances it would

be advantageous to remove orientation as a test variable.Therefore, it was proposed that a direct comparison of the

damage caused by a spherical substitute bird and the damage

caused by a real bird be conducted.

2. PROGRAM OBJECTIVES

The experimental program described in this report wasdesigned to validate a substitute bird and recommend it fordevelopment and qualification of aircraft transparencies. To

achieve this objective, 450 g spherical substitute birds and

real birds were launched at a 90 x 60 x 0.635 cm flat polycar-bonate panel at a 25 degree angle of incidence, and at four

impact locations; center, edge, and two corners. Then, thedata collected from this task and from task II, where the

effects of orientation at impact were studied, were used in ananalysis to quantitatively compare the target damage inflicted

by cylindrical substitute birds, spherical substitute birds,

and real birds. In addition, 60 and 600 g spherical substitute

birds were launched onto rigid flat plates, where temporal and

spatial distribution of loads were measured, at three impact

2. Challita, A., and B.S. West, "Effects of Bird Orientationat Impact on Load Profile and Damage Level," AFWAL-TR-80-3009, June 1980.

3

angles (90, 45, and 25 degrees) and at three velocities (100,

200, 300 m/s). This was accomplished in order to investigate

the scaleability of the substitute bird material.

4

SECTION IIEXPERIMENTAL TECHNIQUES

The experimental work described in this report was conductedat the University of Dayton Research Institute. This section

contains a description of the experimental techniques used to

launch 450 g spherical bird substitutes (gelatin with 10 percentporosity) and real birds (pigeons) onto nominal 0.635 cui flat

polycarbonate panels at an impact angle of 25 degrees. Techniquesused to obtain temporally resolved pressure measurements during

spherical bird substitute impact onto a rigid steel target plateare also described. Descriptions of the experimental ranges,

launch techniques, target structure, instrumentation, and data

collection are given in the sections that follow.

1. LAUNCH TECHNIQUES

Soft body launchers must be capable of accelerating packages

(projectile and sabot) of a required mass to a required velocity

without inducing any projectile breakup or severe distortionprior to impact. Also, projectiles must be launched with

controlled orientation (preferably with zero pitch and yaw).Therefore, launch techniques were developed with which projec-

tiles of up to 3.6 kg could be launched at velocities up to

approximately 300 m/s.

Two systems were used: a 177.8 mm bore and an 88.9 mm bore

compressed gas gun. The large bore gun was used to launchprojectiles with diameter greater than 76.2 mm. A description

of both systems follows.

a. The 177.8 mm Bore Launcher

A detailed description of this system was reported by

the author in References 2 and 3, and can be summarized as being

2. Challita, A., and B.S. West, "Effects of Bird Orientation atImpact on Load Profile and Damage Level," AFWAL-TR-80-3009,June 1980.

3. Challita, A., and J.P. Barber, "The Scaling of Bird ImpactLoads," AFFDL-TR-79-3042, June 1979.

5

composed of a 177.8 mm bore compressed gas gun with supporting

compressor, instrumentation, and control systems. An overall

view of the 177.8 mm gun range is shown in Figure 1. The gun

range consists of:

(1) A storage tank used for driving the gun.

(2) A standard butterfly valve system with a pneumaticactuator located between the storage tank and thebreech of the gun, which was designed to valve thehigh pressure gas from the driving storage tank intothe gun to operate it.

(3) Two 4.88 m long, 177.8 mm, ID heavywall tubes connectedtogether via a locating ring and flange system, and Isupported on two heavy I-beams bolted to the floor.

(4) A vent section connected to the muzzle of the guntube and designed to release the driving pressurefrom the back of the projectile package.

JI

"o ~Figure 1. Overall View of 177.8 mm Gun Range

-- 6FIguel.OverlllVew o1778lmmGunlang lpI

(5) A muffler which encloses the vent section anddeflects the venting gases harmlessly toward thefloor.

(6) A sabot stripper tube which consists of a steel tubewith an initial ID of 177.8 mm that progressivelyreduces, and has a series of longitudinal wide slotscut into it to facilitate the rapid release of thedriving pressure, thus reducing the forces requiredto decelerate and stop the sabot.

The 177.8 mm gun range was used during this experimen-

tal task to launch 450 g spherical bird substitutes onto 0.635 um

flat polycarbonate panels, and 600 g spherical bird substitutes

onto a rigid steel target plate. The sphere was placed in a

sabot for launching. The sabot was a 177.8 mm OD foam plastic

cylinder with a hemispherical cavity in front made to accept

the spheres. The diameters of the 450 and 600 g spheres were

97.0 mm and 107.95 mm respectively. These sabots are shown in

Figure 2.

Figure 2. Foam Plastic Sabots Used for Launching SphericalBirds

7

b. The 88.9 mm Bore Launcher

This launcher was also described in detail by the

author in Reference 2. The 88.9 mm bore compressed gas gun

consists of a 3.66 m long tube supported on two heavy I-beams

bolted to the floor. It uses the same compressor as the

177.8 mm gun, and has a similar storage tank and butterfly valve

system with a pneumatic actuator used to drive and operate the

gun. A sabot stripper section was attached to the muzzle of

the launcher, which consisted of an 88.9 mm ID steel tube with

a series of longitudinal slits cut into it. Compression rings

were placed around the outside of the tube and the ID was

progressively reduced. An overall view of the launcher is

shown in Figure 3.

I -

Figure 3. Overall View of the 88.9 mm Gun Range


j8

The 88.9 mm bore compressed gas launcher was used to

launch 450 g real birds (pigeons) onto 0.635 cm flat polycar-

bonate panels and 60 g spherical bird substitutes onto a rigid

steel target plate.

2. TARGET DESCRIPTION

Two types of targets were used in this experimental program;

flat rigid steel target plates and flat polycarbonate panels.

The steel plates were impacted with 60 and 600 g spherical sub-

stitute birds and the polycarbonate panels with 450 g real and

spherical substitute birds.

The steel plates were used to characterize the impact loads

exerted by spherical substitute birds. Two different plates

were used; one was installed on the 177.8 mm gun range and was

used to characterize the loads of the 600 g spheres. It was

a disk, 50.16 cm in diameter and 9.21 cm thick. A series of

0.635 cm holes were drilled along two orthogonal axis of the

plate at 2.54 cm intervals. These holes were designed to

accept the pressure transducers which were mounted flush with

the surface; up to seven transducers were needed to cover the

area of impart. The second plate was installed on the 88.9 mmgun range and was used with the 60 g spheres. Like the firstplate, it was a steel disk, 30 cm in diameter and 7 cm thick with

holes drilled along two orthogonal axis, at 1.27 cm intervals,

designed to hold pressure transducers; up to five transducers

were needed to cover the area of impact.

The polycarbonate panels were used to investigate the

relative damage potential of nominal 450 g real and spherical

substitute birds impacting at a 25 degree angle of incidence.

The panels were 90 cm long, 60 cm wide, and 0.635 cm thick;

and were rigidly attached to a mounting frame which in turn

was bolted, at a 25 degree angle to the projectile trajectory,

to a structural steel frame. The panels, mounting frame, and

structural support are the same used in a previous experimental

9

program where the effects of bird orientation at impact were

studied and reported by Challita in Reference 2. Real birds

were tested on the 88.9 mm gun range and spherical substitute

birds on the 177.8 mm gun range. Structural frames used with

both the 88.9 mm and the 177.8 mm gun range are shown respectively

in Figures 4 and 5.

3. VELOCITY AND ORIENTATION MEASUREMENT

The velocity of the bird was measured prior to impact using

a simple time-of-flight technique. Between the muzzle of the

sabot stripper and the target, two helium/neon laser beams were

Figure 4. Support Structure and Mounting Frame Used With the88.9 MM Gun


10

0- -

Figure 5. Support Structure and Mounting Frame Used with the177.8 mm Gun

directed across the trajectory. When the bird interrupted the

first laser beam, a counter was started. The counter was

stopped when the bird interrupted the second laser beam. The

distance between the laser beams and the elapsed time were used

to calculate the velocity. To increase the accuracy of the

velocity measurements and to monitor bird orientation and integ-

rity prior to impact, two orthogonal pulsed x-ray systems were

set up at each laser beam station. The resulting x-radiographs

of the bird in flight were used to accurately establish the

position of the bird with respect to the laser beams and to

monitor the condition and orientaticn of the bird. This tech-

nique proved completely satisfactory for measuring bird velocity

and orientation; velocities were measured to within 1 percent,

orientation was determined to within 0.5 degrees. A typical

x-radiograph of a spherical substitute bird is shown in Figure

6.

Ir

Figure 6. X-radiograph of a Spherical Substitute Bird in Free 1Flight

In addition to x-radiograph coverage of the bird in flight, jjhigh speed motion picture coverage was also obtained for selected

shots. Cameras with framing rates of up to 7,000 f/s were

employed for specific investigations of the behavior of the bird

and panel during impact. Sections of film taken during thefirst shot conducted with spherical bird substitutes are shown

in Figure 7.

4. PRESSURE MEASUREMENTS AND RECORDING

During bird impact, the shock pressure can be extremely

high; the duration of the impact is relatively short and there

can be important pressure excursions. The pressure sensing

devices must be capable of measuring and withstanding these

high pressures and the pressure sensing and recording equipment

must have adequate bandwidth to detect and record important

pressure transients.

12

jPANEL P JýECTILE

STRIPPER TUBE

Figure 7. Sections of Film Taken Durino the First Shot Con-ducted with Spherical Bird Substitutes

13

Piezoelectric quartz pressure transducers were used as

the basic sensing devices for these experiments. These trans-ducers have a compact impedance converter physically locatedin the coaxial line close to the crystal; they have a specifiedpressure range of 0 to 700 MN/m2 , and a specified band widthfrom 0 to 80 kHz. Since these transducers are not specificallydesigned for impact testing, calibration was necessary to verifytheir operation. A calibration method for the transducers wasdeveloped to verify the applicability of the manufacturer'scalibration data to the unidirectional axial loads anticipated.The details of these calibration techniques were reported byBarber in Reference 5. A device was fabricated to enable theunidirectional axial loads similar to bird/plate impact loadsto be applied to the transducer. Then, measurements were takento determine the response of the transducers. It was concludedthat the transducers provide reliable, accurate pressure dataover the range of pressures and frequencies expected. Thetransducers were mounted flush with the surface of the steelplates described earlier.

The pressure signals were recorded using an electronic

digital memory system. This system uses an analog to digitalsignal converter. The system has a 300 kHz sample rate, andthe capability to store 2048 data points in shift registerson each of ten channels. The analog pressure signals were dis-played on an oscilloscope, as a function of time, and the timeinterval of interest determined. Then, digital data over theseintervals were recorded on a cassette and were printed out onan electronic data terminal. This technique significantlyincreased the accuracy and reliability of the data.

5. Barber, J.P., J.S. Wilbeck, and H.R. Taylor, "The Charac-terization of Bird Impacts on a Rigid Plate: Part, I,"AFFDL-TR-75-5, AD A021142, January 1975.

14

r

SECTION III

EXPERIMENTAL RESULTS

For a substitute bird to be accepted by the transparency

design and development conmiunity. it has to generate substan-

tially the same impact loads, and produce the same transparencydamage as a real bird. Previous studies demonstrated that gela-

tin with 10 percent porosity is an adequate bird substitutematerial.

Temporal and spatial loads were measured for right circularcylindrical gelatin substitute birds with length to diameter

ratio equal to two. These tests demonstrated that cylindrical

birds generate similar loads to real birds when launched withend-on (axial) orientation. But, for many testing circumstances,it would be advantageous to remove orientation as a test variable.

Therefore, this program task was undertaken to collect damage datainflicted by spherical substitute birds and real birds to be

used in a direct comparison analysis with the data collected ir,a previous program where damage potential of cylindrical substi-

tute birds was studied. As a result of this analysis, one ofthe two substitute bird geometries will be recommended for future

development and qualification testing of transparencies. Tofurther document and verify the scalability of the large birddata, pressure measurements of 60 and 600 g bird substitutes

were also conducted.

1. TARGET DAMAGE STUDIES

The objective of this task was to document and compare thetarget damage inflicted by spherical substitute birds and real

birds as a function of impact location.

A total of 47 shots were conducted in this task; 25 shots

with nominal 450 g spherical substitute birds, and 22 shots with

nominal 450 g real birds (pigeons). The spheres were 9.7 cm indiameter and had a density of 0.96 g/cm3 , which is similar to

15

a n | || | |I

the density of real birds and equal to the density of the 450 g

cylindrical substitute birds used in a previous program and reported

by Challita in Reference 2. The spheres were molded very homo-

geneously as can be seen from Figure 8. Projectiles were launched,

with end-on orientation, onto a nominal 90 cm long, 60 cm wide, and

0.635 cm thick polycarbonate panel at a 25 degree angle of incidence.

The panel was bolted to a relatively rigid support structure as

outlined in Section II. Four impact locations were investigated;

center panel, down-stream center edge, and up-stream and down-

stream corners. These locations, which are shown in Figure 9,

were selected to span the range of relatively unconstrained

impact (center panel), to constraint on two sides of the impact

point (corner impact). The selected conditions generally corre-

spond to conditions present at locations of interest on typical

aircraft transparency systems. The panels, support structure,

Figure 8. Spherical Substitute Bird Cut into Four Pieces toShow Its Homogeneity I


16

I Ii

I I

I I

I I

OBTUSE A ISIDE

i.-TAJECTORY I

EDGEI11.25cm i

I

DOWN-

SIDE

UP-STREAMCO)RNER

1l1•.2:5cm

Figure 9. Impact Locations of Real and Substitute Birds ontoPolycarbonate Panels.

17

and impact locations are the same as those used in phase II andreported by Challita in Reference 2.

The ballistic limit, or the minimum perforation velocity,was used as the primary criterion for measuring the target

damage. Secondary criteria such as the length of cracks, widthand depth of the plastic pocket, and the maxim%m plastic defor-mation were used when perforation wasn't achieved. Perforation

wasn't achieved at either the center p,.:l or the up-stream

corner locations.

a. Summary of Results

A summary of the tests conducted during this experi-mental program is presented in Table I. Projectile material,impact location, impact velocity and a description of theresultant target damage are included in Table I. Photographsof the post test panels used to compare the potential damage of

the spherical substitute birds and real birds are presented inAppendix A, i.e., photographs of the panels impacted at the

center edge and down-stream corner at velocities above and

below the threshold velocity, and photographs of panels impactedat the center panel and the up-stream corner that show con- Isiderable amount of deformation.

The perforation velocity at the center edge location

was found to equal 190 + 2 m/s for spherical substitute birds,and 212 + I m/s for real birds. At the down-stream corner,

the perforation velocities were 182 + 4 m/s for spherical sub-stitute birds, and 192 + 1 m/s for real birds.

Perforation was not achieved at either the center

panel location or the up-stream corner location. Examinationof the center panel shot numbers 5-0200 and 4-0156 shows thatthe real bird causes more plastic deformation than the spherical


18

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bird; even though the spherical substitute bird was launched20 m/s faster than the real bird. Similarly, examination of theup-stream corner shot numbers 5-0211 and 4-0164 (spherical sub-stitute bird was 13 m/s faster than the real bird) clearly in-

dicates that the real bird causes more plastic deformation thanthe spherical substitute bird.

b. Comparison of Damage Inflicted by Real and

Substitute Birds JThe objective of this study was to conduct a direct

comparison of the post-test panels, impacted by real and sub-

stitute birds, in order to recommend a substitute bird fordevelopment and proof testing of transparencies.

Polycarbonate panels were impacted with three dif-ferent projectiles (right circular cylinders, spheres, and real

birds) and five sets of damage data were collected. In a pre-vious experimental program, reported by Challita in Reference 2,right circular cylinders were launchcd onto polycarbonate panels

with three different orientations in order to study the effectsof orientation at impact on damage level. Perforation velocitywas used, when applicable, as the main criterion for damagecomparison. A summary of the perforation velocities for variousprojectile materials and orientations are presented in Table II. '.

In Reference 2, right circular cylinders with end-on orientationwere found to be the most damaging orientation; therefore, ourcomparison will be limited to right circular cylinders with

end-on orientation.

Prior to discussing the results of this comparison,

some factors affecting these results should be pointed out.

First, it should be noted that the time-loading histories of

the panel during a spherical impact and a real bird impact or


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an end-on cylinder impact are different. The impact durationof a sphere is shorter than the impact duration of a real birdor an end-on cylinder of the same mass, density, and velocity.The impact duration is directly proportional to the effective jbird length which is smaller for spheres than it is for realbirds and end-on cylinders. Also, the loaded area during impactis larger for a sphere than it is for a real bird or end-oncylinder. Thus, for similar energy level impacts, the spheresgenerate higher strain rates in the material, and consequently,it should be expected to see different structure-panel responsefrom real bird or end-on cylinder impacts to spherical impacts.

The comparison will be conducted as a function ofimpact location. Each location will be considered separatelyand the damage potential of various projectiles will be

evaluated.

Center edge:

Panels impacted with real birds and end-on cylindersshowed very similar deformation and perforation velocity. Panelsimpacted with spheres showed less total plastic deformation andhad lower perforation velocity than both real birds and end-oncylinders. The plastically deformed surface of the panel

impacted with a sphere was not as smooth as for the other twocases. This may be attributed to the strain rate sensitivityof the panel. For similar input of energy levels, spheresexhibit higher strain rates during impact because of theirshorter impact duration. Impact duration is directly propor-tional to the effective bird length which is equal to 23.1 cmfor spheres and 28.5 cm for end-on cylinders (for a 25 degreeimpact angle).

Down-stream corner:

Panels impacted with end-on cylinders have the lowestperforation velocity. These panels showed more plastic flowthan gelatin spheres. They have deeper pockets at lower energylevels.

27

Panels impacted with real birds showed the most plas-

tic flow; but they were at higher energy levels than the end-on

cylinders and spheres.

Panels impacted with spheres showed similar defor-

mation and perforation velocity to panels impacted with flat-on

cylinders. The plastically deformed surfaces were not as

smooth as either real birds or end-on cylinders.

Center panel:

Panels impacted with gelatin spheres had less plastic

deformation than panels impacted with end-on cylinders or real

birds, even though the spherical impacts were at higher energy

levels.

Panels impacted with real birds at velocities higher

than 300 m/s showed slightly raore pronounced finger-shaped

ridges (local buckling) than panels impacted with end-on

cylinders. This is another situation where the panel sensitivityto strain rate might have had an effect on the damage. It was

observed that at velocities higher than 300 n/s the cylinders

stretch to an in-flight L/D > 2. Real birds had an in-flightL/D =2.

Up-stream corner:

Panels impacted with spheres exhibited the least

amount of plastic deformation compared to panels impacted with areal birds and end-on cylinders. Real birds produced more pro-

nounced finger-shaped ridges, around the plastic pockets, than

end-on cylinders. No ridges were observed with sphericalimpacts. At the highest velocity launched, real birds produced

deep pockets compared to the pockets by end-on cylinders. The

end-on cylinders produce3d wider pockets.

The damage comparison at the center panel and up-

stream corner shows that spheres cause less plastic deformation

than real birds and cylindrical substitute birds, and the damage

28

II

Comparison at the center edge and down-stream corner shows that

spheres have lower perforation velocity than real birds. Thelatter result was attributed to the strain rate sensitivity of

the panel (spherical impacts generate higher strain rates thanend-on or cylindrical impacts) and to the structure-panel

response (edge effects). Spherical substitute birds hit the

panel a lot closer to the edge than real birds and cylindrical

substitute birds; i.e., spheres hit approximately O.S in. from

the edge compared to 1.8 in. for end-on cylinder. This is

mainly because its diameter is larger than the other two

(Figures 10 and 11).

The results of this comparison can be summarized

as:

(1) End-on cylinders cause similar damage to peal

birds and are more damaging than spheres at the center panel

and the up-stream corner locations.

(2) End-on cylinders are as damaging as real birds

on the center edge location and more damaging th&n rea! birds

at the down-stream corner.

(3) Spheres have lower perforation velocity than

real birds at the down-stream corner and center edge locations

and have lower perforation velocity than end-on cylinders at

the center edge. This is attributed to the edge effects and

to the strain rate sensitivity of the panel.

(4) Irregularities in the plastically deformed

region decrease with increasing impact duration. Thus, longerprojectiles result in smoother deformation.

2. SPHERICAL SUBSTITUTE BIRD LOADING STUDIES

A total of 55 shots were performed to investigate and

document the. effects of geometry on impact loading. The p-o-

jectiles used were 60 and 600 g spherical substitute birds

(gelatin with 10 percent porosity). Projectiles were launched

29

| | | | | | | || |

BIRD TRAJECTORY A

S/a •-EDGE OF PANELIt

CENTER IMPACT

I/ l ONE POUND SPHERICALPOLYCARBONATE SUBITUTE BIRD

PANEL

5.85.

Figure 10. Projection of a 1-lb. Spherical Substitute Birdonto a Polycarbonate Panel at 250 Angle of Incidencewhen Impacting the Center Edge Location

BIRD TRAJECTORY I"-'1 EDGE OF PANEL

"CENTER IMPACT

ONE POUND CYLINDRICAL

SUBSTITUTE BIRD

POLVCARBONATEPANEL

Figure 11. Projection of a 1-lb. Cylindrical Substitute Birdwith End-on Orientation onto a Polycarbonate Panelat 250 Angle of Incidence when Impacting the CenterEdge Location.

30

I... ..-• _,.,. ,. • ... •

at velocities of 100, 200, and 300 m/s onto a steel target

plate at three impact angles; 90, 45, and 25 degrees.

Time varying pressure data were collected using a digital

memory system as described in Section II. Peak pressure and

impact duration were measured from t hese recorded data. The

results of these measurements, together with comparisons to

theoretical predictions are presented in the following sections.

a. Pressure-time History

Bird impact on a rigid plate can be characterized as

a fluid dynamic process having four distinct phases. The first

phase is the initial impact phase during which very high shock

pressures are generated between the bird and the target. The

release of the shocked material results in a decaying pressure

during phase two. The shock pressure decays to a steady-state

pressure which characterizes phase three. During this phase,

the bird flows steadily onto the plate and is regarded as jet

flow. The fourth phase of the impact occurs when the trailing

end of the bird approaches the plate and the pressure drops to

zero. These phases were discussed in detail in Reference 4

by Barber, Reference 3 by Challita, and Reference 1 by Wilbeck

and were found adequate to describe the impact of a real bird

and cylindrical substitute bird with length to diameter ratio

equal to two when launched with end-on orientation on a rigid

plate.

Typical pressure traces of spherical substitute

birds impacting a rigid steel target plate at normal and oblique



4. Barber, J.P., J.S. Wilbeck, and H.R. Taylor, "Bird ImpactForces and Pressures on Rigid and Compliant Targets,"AFFDL-TR-77-60, flay 1978.

31

angles of incidence are presented in Figures 12 and 13. A peak

pressure rise and decay can be seen on these traces. Unlike

the real or cylindrical substitute bird impacts, no plateauindicative of steady-state flow is observed.

During the initial impact, the particles on the front

surface of the projectile are instantaneously brought to rest

relative to the target face and a shock wave propagates into ithe projectile. As this shock wave propagates into the projec-tile, it brings the material behind the shock to rest. The

pressure in the compressed region is initially very high and

uniform across the impact area. The outer surface of the pro-

jectile is a free surface and the material near this surface

is subjected to a very high stress gradient. This stressgradient causes the material to accelerate radially outward and

a release wave is formed and propagates inward. The arrival

of this release wave at the center of impact marks the end of

the initial impact and the beginning of the decay process. The

pressure behind the shock, or the Hugoniot pressure, depends on

the projectile density, shock velocity, and the impact velocity.

The Hugoniot pressure was derived by Wilbeck in Reference 1

and is given by:

P P V Vsn

where; p = density of the projectile

Vs = shock velocity

Vn = normal component of the impact velocityni

Vn is equal to the impact velocity, V, for normal impacts, and

equal to V sin 0 for oblique impacts (6 is the impact angle).

The shock velocity, V8 , corresponding to the normal component

of the impact velocity Vn should be used for oblique impacts.

Wilbeck in Reference 1 derived the relation between the shock


32f

V=99.0 m/sm -602 g 2 _P=43.23 MN/Mu-cm m (a)t=2000js/cm

W

Time Mt)

V=202 m/sm=595 g 2 (b)P=78.3 MN/M -cm ,t=2000 ps/cm

I0$4

Time Mt

V=304 m/sm=600 g 2 (c)P=53.78 MN/m -cmt=2000 us/cm

04

Time (t)

Figure 12. Typical Pressure-Time Record of Nominal 600 y SphericalSubstitute Bird (Gelatin with 10 Percent Porosity).(a) 900 impact, center transducer; (b) 450 impact,3" below center; (c) 250 impact, 2" below center

33

V=196 rn/s 00jM=60 g 2 4P=44.5 MN/rn -cm U) (a)t=2000 las/cm I

V=285 rn/sm=60 g 2P=43.0 MN/rn -Cm

(t=2000 Ps/cm (b))

Time (t)

V=297 rn/sm=60 g 2P=21.3 MN/m -cmn N

ct=2000 I's/cm (C)

Time (t)

Figure 13. Typical Pressure-Time Record of Nominal 60 gSpherical Substitute B~ird (Gelatin with 10 Per-cent Porosity). (a) 900 impact; center trans-ducer; (b) 450 impact; 2" below center;(c) 250 impact; 3" below center

34

velocity and the impact velocity for gelatin with 10 percent

porosity.

The initial impact pressures measured for all normal

and oblique impacts of 60 and 600 g gelatin spheres are presented

along with the corresponding theoretical Hugoniot pressure in

Figures 14, 15, and 16. The measured impact pressures for the600 g spheres agree fairly well with the theoretical Hugoniot

pressure for all impact angles. The measured impact pressures

for the 60 g spheres were, as expected, lower than the calculated

values. This departure from predictions is attributed to the

limited bandwidth (80 kHz) of the pressure transducers used.

Peaks may have been clipped because of the relatively shorter

duration of the shock pulse in these impacts which is a function

of the size of the projectile and the impact velocity.

As the shock propagates into the projectile, a radial

release wave propagates in toward the center of the projectile

from the free surface edges, and a decay process is formed when

the release waves converge at the center of impact. In an

end-on cylinder or real bird impact, the decay process is over

well before the trailing end of the bird reaches the target,

and a- steady-state flow is established. The steady flow is

finally terminated when the end of the bird reaches the target.

In contrast, Hugoniot pressure is still decaying as the trailing

edge of the spherical substitute bird reaches the target. This

can be seen from the pressure traces in Figures 12 and 13 where

the shock pressure decays to zero and no pressure plateauindicative of the steady-state process is observed.

35

400

THWRTICALpo HUIDIT FOR

KftE GELATIN/ S' eRE'TICAL

* V rI500 )

00 50 1O0 0 1 0050 0 q00 350

IMPACT VELOCITY (m/sl

Figure 14. Comparison of Measured Peak Pressures to Theoretical-luvgoniot for 60 and 600 g Spherical Substitute|

Bird at Normal Impact

I

300-

250 1030 / n

00

,&200 0 T IORETICAL

GELATIN WITHISO-, 10%O POIROSITY

0 50 100 150 200 250 300IMPACT VELOCITY (m/s)

Figure 15. Comparison of Measured Peak Pressures to TheoreticalHugoniot for 60 and 600 g Spherical SubstituteBird at 45o Impact

36

a. . mmm sml

-200E * 60g SPHERES

2150 ( 600g SPHERES•-O OunT For0.%

GELATIN WITH

501 %

0)

0 50 100 150 200 250 300 350IIMPACT VELOCITY (m/s)

Figure 16. Comparison of Measured Peak Pressures to TheoreticalHugoniot for 60 and 600 g Spherical SubstituteBird at 250 Impact

3

Ii

SECTION IV

CONCLUSIONS AND DISCUSSION

A large and detailed body of impact pressure and damagepotential data now exists for real birds and bird substitutes

(gelatin with 10 percent porosity) over an enormous range ofimpact parameters. The parameters and their ranges are:

(1) Real and substitute bird mass - 60 g to 3600 g.

(2) Impact velocity - 50 m/s to 325 m/s.

(3) Impact angle - 25, 45, and 90 degrees.

(4) Geometry of substitute bird - right circular

cylinders with L/D = 2 and spheres.

(5) Orientation of cylindrical substitute birds at impact -

end-on, flat-on, and side-on.

(6) Target - rigid and compliant.

This entire body of data has been analyzed and the important

impact processes identified, functional relationships between

the impact pressures and impact parameters identified, scaling

of impact loads with bird mass concluded, effects of orientationat impact studied and worst-case orientation identified, and

comparisons of damage potential of real and substitute birds

completed. From the work reported here, the following conclu-sions may be drawn.

(1) Gelatin with 10 percent porosity is an adequate sub-stitute bird material.

(2) Impact pressure measurements of spherical substitute

birds did not exhibit any steady-state flow condition.

(3) Of the three projectiles tested (end-on real birds,

spheres, and end-on right circular cylinders) spheres produced

the least amount of plastic deformation at the center and

up-stream corner locations.

38

(4) Spheres had the lowest perforation velocity at the

center edge and had a lower perforation velocity than end-onreal birds at the down-stream corner. This was attributed tothe edge effects and to the strain rate sensitivity of thepanels tested.

(5) End-on cylinders showed similar perforation veloci-

ties and damage potential to end-on real birds.

(6) End-on cylinders are better substitute birds than

spheres.

For convenience and completeness of the report, a summaryof the conclusions and findings reported in previous work byChallita in References 2 and 3, by Barber in References 4 and 5,

by Wilbeck in Reference 1, and by Bauer in Reference 6 will belisted here.

(1) Real birds behave as a fluid during impact at theimpact velocities of interest in birdstri!e (>75 m/s).

(2) There are four phases of fluid behavior during a real

and end-on cylindrical substitute bird impact event; the shockphase of initial impact, shock pressure decay, steady flow,and termination.





5. Barber, J.P., H.R. Taylor, J.S. Wilbeck, "Characterizationof Bird Impacts on a Rigid Plate: Part I," AFFDL-TR-75-5,January 1975.

6. Bauer, D.P. and J.P. Barber, "Experimental Investigation ofImpact Pressures Caused by Gelatin Simulated Birds and Ice,"UDR-TR-78-114, November 1978.

39

(3) Peak shock pressures are independent of bird mass

but depend in a predictable manner on impact velocity, impact Iangle, and bird material properties.

(4) Steady flow pressures are independent of bird mass

but depend in a predictable way on impact velocity, impact angle

and bird material properties.

(5) The spatial distribution of bird impact pressures

scale linearly with bird dimensions (providing bird orientationat impact is fixed).

(6) Impact duration is given by simply dividing the

"effective bird length," which is a function of impact angle

and bird orientation, by the impact velocity.

(7) Of the three impact orientations of the right cir-cular cylinders tested (end-on, flat-on, and side-on) side-onwas the least critical and end-on was the most criticalorientation.

(8) During end-on birdstrike testing pitch and/or yaw

of the bird would tend to decrease criticality.

40-----

---------! .Jl -w. ia va IIrd _ I I l - • _-.• . . .

SECTION VRECOMMENDATIONS

It is recommended that:

(1) Right circular cylinders with length-to-diameter

ratio equal to two be used as the substitute bird for alldevelopmental and qualification testing of transparencies.

(2) Gelatin with 10 percent porosity be used as the

substitute bird material. The bird substitute specificationsare preserted in Appendix B.

(3) Additional damage tests be conducted as a functionof edge proximity to give the designer a better insight on the

transparency-structure response.

(4) A research program be conducted using larger birdsto determine the perforation velocities for the center paneland up-stream corner locations to eliminate any doubt about

the similarity of the damage potential of the end-on cylinders

and real birds.

i

*1

,I

ii

I

|I j

(a)

(b)

ri.iurc A-1. Shot 14o 5-0195; Panel Iinpitcted at the Centecr Edge;

One-Pound Spherical c-elatil: Launched at 192 rn/s.

(a) front view; (b) end view

43

(a)

(bj _

I al, P-"--

Figure A-2. Shot No. 5-0196; Panel impacted at the Center Edge;

one-Pound Spherical Gelatin Launched at 188 rn/s.


44

, •, • -

(a)

(b)

WI

t m

I .r

Figure A-3. Shot No. 5-0197; Panel Impacted at the Center Panel;

One-Pound Spherical Gelatin Launched at 304 m/s.


45

(a)

(b)

Figure A-4. Shot No. 5-0199; Panel Impacted at the Center Panel;

One-pound Spherical Gelatin Launched at 320 m/s.


46

(a)

(b) -

Figure A-5. Shot No. 5-0200; Panel impacted at the Center Panel;

One-Pcund Spherical Gelatin Launched at >325 rn/s.(a) front view; (b) end view

47I

(a)

(b ).......

Figure A-6. Shot No. 5-0203; Panel impacted at the Down-Stream1

Corner; One-Pound Spherical Gelatin Launched at

169 rn/s. (a) front view; (b) end view

48

(a)

Figure A-7. Shot No. 5-0208; Panel Impacted at the Down-StreamCorner. One-Pound Spherical Gelatin Launched at186 rn/s. (a) front view; (b) end view

49

(b)

Figure A-B. Shot No. 5-0210; Panel Impacted at the Up-StreamCorner; One-Pound Spherical Gelatin Launched at305 rn/s. (a) front view; (b) end view

50

(a)

__0

(b)

-A

Figure A-9. Shot No. 5-0211; Panel Impacted at the Up-StreamCorner; One-Pound Spherical Gelatin Launched at321 rn/s. (a) front view; (b) end view

(a)

(b) __

r-igre -10.Sho No 4-047;Pane Imactd attheCentr E~jeone-oun Pieon aunhedat 13 Ms. a) ron

vibw (b nd ve

52I

(a)

(b)

Figure A-11. Shot No. 4-0150; Panel Impacted at the Center Edge;One-Pound Pigeon Launched at 211 rn/s. (a) front

view; (b) end view

53

. -

(a)

(b)

Figure A-12. Shot No0. 4-0156; Panel impacted at the Center Panel;

view; (b) end view

54

A/(a)

(b)

Figure A-13. Shot No. 4-0157; Panel Impacted at the Center Panel;One-Pound Pigeon Launched at 313 m/s. (a) frontview; (b) end view

55

Figure A-14. Shot No. 4-0158; Panel Impacted at the Center Panel;One-Pound Pigeon Launched at 294 ni/s. (a) frontview; (b) end view

56

(a)

(b)

rig-aure A-I5. Shot No. 4-0160; Panel Impacted at the Down-StreamCorner; One-Pound Pigeon Launched at 191 rn/s.(a) front view; (b) end view

57

(a)

. .

(b)__

Fiur A-6 ht11406;Pnl matda h onSraCornr; ne-PundPigen Lunchd a 193i/1(a) font vew; b) en vii

58I

(a)

.11

Figure A-17. Shot No. 4-0164; Panel Impacted at the Up-Stream

Corner; One-Pound Pigeon Launched at 308 rn/s.

(a) front view; 1,b) enct view

59U

(a)

(b)

I,- IFigure A-18. Shot No. 4-0165; Panel Impacted at the Up-Stream

Corner; One-Pound Pigeon Launched at 306 m/s.(a) front view; (b) end view

60

APPENDIX B

BIRD SUBSTITUTE SPECIFICATIONS

6

I

61I

- I-- i,-----

APPENDIX BBIRD SUBSTITUTE SPECIFICATIONS

From the work reported here and in References 1 by Wilbeck,

2 and 3 by Challita, and 4 and 5 by Barber, the following birdsubstitute specifications are proposed.

(1) The material of the bird substitute has to be gelatinwith 10 percent porosity. It is recommended that an industrialgrade gelatin (275 Bloom type A) be used; it is also recommended

that phenolic microballoons (material type BJO-0930) be used toget the required porosity.

(2) The geometry of the bird substitute has to be a

right circular cylinder with a length to diameter ratio approxi-

mately equal to two (+ 0.05).

(3) The bird substitute has to be homogeneous. Hgqh

density gradients within the bird substitute are not acceptable.3The recommended density is 0.96 g/cm ; the maximum density

variation within the bird substitute should not exceed 0.04.

1. Wilbeck, J. S., "Impact Behavior of Low Strength Pro-jectiles," AFML-TR-77-134, July 1978.

2. Challita, A. and B. S. West, "Effects of Bird Orientationat Impact on Load Profile and Damage Level," AFWAL-TR-80-3009, June 1980.

3. Challita, A. and J. P. Barber, "The Scaling of Bird ImpactLoads," AFFDL-TR-79-3042, June 1979.

4. Barber, J. P., J. S. Wilbeck, and H. R. Taylor, "Bird ImpactForces and Pressures on Rigid and Compliant Targets,"AFFDL-TR-77-60, May 1978.

5. Barber, J. P., H. R. Taylor, and J. S. Wilbeck, "Charac-terization of Bird Impacts on a Rigid Plate: Part I,"AFFDL-TR-75-5, January 1975.

62

REFERENCES





5. Barber, J.P., H.R. Taylor, J.S. Wilbeck, "Characterizationof Bird Impacts on a Rigid Plate: Part I," AFFDL-TR-75-5,January 1975.

6. Bauer, D.P. and J.P. Barber, "Experimental Investigation ofImpact Pressures Caused by Gelatin Simulated Birds and ice,"UDR-TR-78-114, November 1978.

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63*Ut.S.GoeVnmgnt Printing Oftie: 1981 - 757"02/441

ap'i - dtic · project 2402, "vehicle equipment technology," task 240203,...

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