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I. Re_o.t _ J 2 Gc,vt_nm*ntAcce.,o. No. 3 Rec,_ent°sC_ta:ogNo

NASA CR..J,74708 I

4. Title e'_ S_ltle 5. Rltl_o,1 DJle

Advanced Turboprop Vibratory Characteristics 6 April F_'fo*m,-g O1984 rpn,tel,o. Code

7 A_thoe(s; I_ I_trfo_m_ng Or_)_n,_et,On Rtpo,1 hi:,

Srinivasan, A. V., and Fulton, G.B. R84-956627-I

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United Technologies Research Center II. Coatr_:t o, Grant No

East Hartford, CT 06108 NAS3-23533

13 TyPe of Report l.d Pe.,o_ C,O,_'_.-

12Soon,:.,, Ag.. _ €N,, ,_,_d*dd,,. Final Science & Technology Section, MS500-305

NASA Lewis ResearcB Center 14soo.,o,,,_Ag,_cod, €,

21000 Brookpark Road, Cleveland OH 44135

15 S_pme,,'_tJ, a Notes

Point of Contact: Robert Kielb, NASA/Lewis Research Center

Cleveland, Ohio 44135 (216)-433-4000 x5104

15 A_1,J:t

The results of an experimental program carried out on an

assembly of SR5 advanced turboprop blades to develop a structura

dynamic data base for swept props are reported. The data was

gathered through a series of tests conducted in a vacuum at

speeds up to 9000 rpm. Steady state blade deformations under

centrifugal loading as well as vibratory characteristics of the

rotor assembly have been measured and compared with analytical

results supplied by NASA. Vibration was induced through a

system of piezoelectric crystals attached to the blades. Data

reduction procedures developed at UTRC were used to provide

deformation, mode shape, and frequencies of the assembly at

_). predetermined speeds.

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Prop-fan, Vacuum spin test, I Unclassified/Same as Report.

i Centrifugal deformation, In accordance with distribution

i Blade frequency response, lists furnished by the NASA

I Blade mode shape, Swept blades. Contracting Off. or Proj. Mgr.

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". Advanced Turboprop Vibratory Characteristics

TABLE OF CONTENTS

ACKNOWLEDGEMENTS ......................... i

I. INTRODUCTION ............... _ ......... I

II. SU._RY ........................... 2

[I[. PROGRAMOBJECTIVES...................... 3

' X_', 'rEST FACILITIES ....................... 4

V. DESCRIPTION OF ROTORAND BLADEGEOMETRY........... 5

t

VI. INSTRUMENTATION ....................... 6

A. Steady Centrifugal Blade Deformation . ......... 6

B. Dynamic Instrumentation ................. 7

C. Blade Excitation, Data Acquisition Systems ....... 8

Vl[. TEST PROCEDURE ....................... IO

A. Steady State Deflections ................ I0

B. Dynamic Testing ..................... II

t

VIII. DISCUSSION ........................ 14

A. Steady State Deflections ................ 14

B. Vibratory Tests ..................... 16

C. Blade Strain Mode Shape ................. 18

IX. MAJOR CONCLUSIONS AND RECOMMENDATIONS ............ 21

X. REFERENCES ......................... 22

TABLES .............................. 23

FIGURES .............................. 33
:- TABLE OF CONTENTS(Cont*d)

.*q.

" _ APPENDIX I - MIRROR/LASERDATA ..........

...... AI-1

APPENDIX II - ANALYSIS OF PHOTOGRAPHSOF BLADETIP VECTORS • • • AII-1

, APPENDIX III - DYNAMIC DATA REDUCTION

.............. AIII-1

APPENDIX IV - SUMMARY OF NASTRAN ANALYSIS °e°eJoeooeeo AIV-!

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ACKNOWLEDGEMENTS

The authorswould like to thank Mr. D. G. Cutts for his efforts in

J_" formulatingthe teat program,and Dr. R• A. Arnoldi for sharinghis valuable

experiencein turbomachinerydynamicsand providingdata reductionsupportand

guidance. The assistanceof Mr. R• J. Haas and Dr• K. A. Stetson in setting

I. up and interpretingthe opticaldata is greatlyappreciated. The efforts of

Mr• J. Zucker in assemblingthe test hardwareand assistingin the experimental activitycontributedto the successof the program. Finally,thanksto

Mrs. C. K. Obee for her assistancein the preparationof the report•

The authors would also like to express their appreciation to R. Kielb,

the NASAFrogram Manager, and C• Lawrence, for their support in supplying the

results of their NASTRANanalyses which provide the basis for comparison with

experimental data•

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I. INTRODUCTION

._- Prop-fan propulsion promises large reductions in fuel burned compared to

, advanced turbofan propulsion, with corresponding reduction in direct operating

costs. Current predictions (Ref. 1) indicate that for a 120 passenger

transport aircraft in the 1990's at a cruise Hach number comparable to that

attainable from turbofans, a single rotation Prop-fan powered aircraft will

burn 20% less fuel and reault in a reduction of I0% in direct operating costs.

Potentially greater benefits are expected with counter rotating Prop-fans

which are predicted to burn 31% less fuel, yielding a 14% reduction in direct

, operating costs. Technology advances in several diverse fields are essential

if these predicted gains in performance are to be realized. Prop-fan use is

contingent upon advances in aerodynamics, acoustics, power transmission, and

structural dynamics technologies.

The present report is a summary of results of a series of experiments

carried out in the UTRC vacuum spin facility. Interest in the experimental

program was raised, when differences between frequencies calculated by

different finite eleme_t codes could not be resolved. Additionally, the

calculated frequencies did not agree wlth the corresponding frequencies

measured at zero speed. The test program was oriented towards acquisition of

both steady and vibratory data at speeds which could be readily compared with

analytical results.

Compared to conventional propellers, Prop-fan blades are thin and highly

swept back which give rise to large bending and twisting deformations and

i complex vibratory characteristics. In addition to a strong correlation

• between aerodynamic performance and centrifugal deformation, the aeroelastic stability and forced response in the transonic Mach number range at which the

blade operates is dependent upon both frequency and vibratory mode shape.

_' Io

The test results reported herein present both steady deformations and

vibratory frequencies and mode shapes of a model prop-fan in a vacuum centrifugal environment. Several unique measurement techniques were exploited

during the program including determination of steady blade deformation by

angular deflection of a laser beam reflected from mirrors bonded to the

blades, and direct tip deflection measurements with high speed strobe photography. Use of piezoelectric crystal excitation provided smooth sinusoida!

blade excitation of the assembly at arbitrary amplitude and interblade phase

angle in the vacuum. Comparison between test results and corresponding

analytical predictions is made and discussed.

Support for these tests was made through the NASA Advanced Turboprop

_ pro_ect office as part of the overall program to develop turboprop technology.

p

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_:..}
II. SUMMARY

_ An experimental program was carried out on an assembly of SR-5 advanced

turboprop blades to develop structural and dynamic data for swept props. The

t data was gathered through a series of tests conducted in vacuum at speeds up

i to 9,000 RPH. Steady state blade deformations under centrifugal loading were

measured with a system comprising an externally mounted laser and blade

I mounted mirrors as well as by direct strobe photos of the blade tips. Vibrai tory characteristics of the system have been measured and comoared with

analytlcal results. Vibration was induced through the UTRC developed system

of piezoelectric crystals attached to the blades. Data reduction procedures

also developed at UTRC were used to provide deformatlon_ mode shapej and

frequencies of the assembly ar predetermined speeds.

\
IIl. PROGRAM OBJECTIVES

This research program pertained to developing structural data aimed at

"serving the design process Of prop-fans, Steady state blade deflections as

well as vibratory characteristics of prop-fans were determined over a speed

range from tests conducted in a vacuum on a model SR-5 prop-fan rotor, The

specific objectives were to:

1. Measure the centrifugally induced steady blade twist and deflection

up to the mechanical design speed of 9,000 RIM.

2. Measure frequency of the first five normal modes of vibration as it

varies with speed.

3. Verify via measurements if the blades are mechanically coupled

throuzh the hub during vibration and determine the character and

extent of that coupling.

4. Compare the experimental results with corresponding analytic_l

predictions supplied by NASA.

The overall goals of the program were to (a) assess the extent of

correlation between finite element analysis and corresponding test results,

and (b) determine the extent of mechanical coupling among the blades through

an examination of the response of the assembly in its system modes.

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IV. TEST FACILITIES

The tests were carried out in the UTRC high speed spxn facility, a I0 ft

diameter by 3 ft high vacuum chamber (fig. I). This chamber is a fabricated

I weldment with 3/4 inch thick shell and 2 inch thick top and bottom cover

plates. A 3 inch thick ring 94 inches in diameter and 34 inches high is positioned inside the chamber to contain fragments from any unanticipated failI ures. The vacuum chamber is mounted on a platform 4 feet above the floor with

I the vertical axis drive system mounted on the bottom plate. This arrangement

"i allows unobstructed visual access to the test piece from the top.

The drive system (fig. 2) is composed of a main drive shaft supported on

two duplex ball bearings. At the top of the drive shaft in the plane of the

chamber floor, is a squeeze film damper to control rotor vibrations during

excursions through resonant speeds. At the lower end of the drive shaft is a

flexible coupling which connects to an 8 inch Barbour-Stockwell air turbine,

controlled by an"electro-pneumatlc servo throttle valve to within ±0.5% of the

specified full speed. A safety interlock system protects against any loss of

oil pressure, oil flow, or oil level in the reservoir. A remotely operated

turbine brake control will function in the event of a power failure. An overspeed trip solenoid air valve will shut off the drive air when the selected

value of maximum speed is attained. A balance air regulator allows a perce_,tage _(ten percent maximum) of the drlve air pressure to support and unload the

turbine bearings.

The vacuum pump system will evacuate a volume of 200 cubic feet to a

vacuum of 20 microns or less with specified leak rate of less than 1.2xlO4

standard cc/sec of helium. The pump system is sized to achieve this vacuum

level in appropriately 20 minutes. An automatic vacuum valve will isolate the

! spin chamber and prevent loss of its vacutnushould a power failure occur. The

bottom flange of the turbine is fitted with a magnetic pick up and 60 tooth

gear to provide the signal to the controller. Below the turbine through

another flexible coupling, the 100 channel Electrotech slip ring is mounted.

The slip ring is rated at 12,000 RPM and has specified max noise level of 6 m_

at 100 ma current at 9,000 RPM.

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V. DESCRIPTION OF ROTOR AND BLADE GEOMETRY

-I The test rotor comprises Ti 6-4 prop-fan blades mounted on a steel hub

"." which retains the blades in the centrifugal field and has provision for fixing

the pitch angl_ of the blades (fig. 3). The SR-5 rotor designed and

fabricated by Hamilton-Standard Division of United TecHnologies Corporation as

a I0 bladed rotor has undergone extensive wind tunnel testing under a variety

of conditions to measure both its aerodynamic and structural characteristics.

This report covers a five bladed version of the SR-5 rotor (fig. 4), with

blades set at the nominal cruise flight pitch angle of 58.5 degrees at a

reference radius of 3/4 Span. Table I is a su_zmaryof the significant airfoil

geometric parameters more completely given in Ref. 2. The individual blades

were moment weighed after the instrumentation and ieadwork was installed and

then mounted in the hub in a sequence to minimize initial imbalance. Table II

summarizes the results of this attempt to minimize unbalance.

The analytical results to which the test data is compared were obtained

by NASA using the NASTRAN finite element model. This analytical program

,. described in detall in Ref. 3 modeled the blade with 881TRIA 3 elements.

_, Both linear and non-llnear solution procedures were used to properly simulate

the large steady deflections and the stiffening effect of the centrifugal

field. Vibratory modes of a single blade were calculated at several speeds

with the NASTRAN. Additional details of the analytical modeling are given in

Appendix IV.

The blade/rotor axis system is shown in Figure 5; the X-axis is

coincident with the rotor axis (positive aft), Y is radial and coincident with

center of the blade pitch change axis (positive outward) and Z is perpendicular to the XY plane (positive in the direction of rotation to complete the

right hand coordinate system). Figure 6 shows the grid breakup used for the

517 node NASTRAN model. For purposes of surface identification, the pressure

or face surface is the surface facing in the positive Z direction, and the

suction or camber surface faces the negative direction.

5
VI. INSTRUMENTATION

A. Steady Centrifugal Blade Deformation

I The technique of measuring propeller deflections by means of reflection

from mirrors bonded to the blade surf=ce was first reported in this country in

NACA report No. 644 of January 18, 1938, Ref. 4. Realization of the full

'!

IF polight tentisalourcoef and this adhesi technique ves wirtequi h hlgn red dstreng evelopment th so ofthatantheintense mirrorsnarrwoowuldbeamremain

attached to the blade in the severe environment. Rpadily available and

inexpensive lasers and epoxy adhesives led to the independent development and

refinement of this technique reported in references 5 and 6. The method of

using reflection of a laser beam from mirrors bonded to the blade was thus a

logical choice to determine the complex deformation patterns of the prop-fan.

The location of the mirrors mounted on the blades is shown in Figure 7

and the schematic arrangement of the laser/mirror shown in Figure 8. One

blade (S/N I0) has the full array of II mirrors as shown in the figure; each

of the other four blades in the rotor have a single mirror at the A-2 location. Alignment and bondin_ of the mirrors were carried out with the blades

mounted in the hub at the specified pitch angle, and the hub mounted in the

spln-rig. The intense narrow beam light source is provided by a Hu_hes,

Series 4000 HeNe laser. The first step required that the laser which was

secured to an alignment frame mounted to the rim of the rig, he aligned so its

axis is radial. The optical bench (fig. 9) assures that the two beam splitting and final fully reflective mirrors are fixed so that the incident beams

are vertical along a radial llne and at the specified radii (7.0 inches (17.7R

cm), 9.5 inches (24.13 cm), and II.5 inches (29.2 cm)). The D row of mirrors

was added subsequent to fabrication of the mirror fixture, consequently, the

laser/ mirror assembly had to be moved radially inward until the innermost

beam engaged the D mirrors at 3.75 inches (9.53 cm) for measurements of these

deflections. During the process of bonding the mirrors to the blades, the

intensity of the laser was reduced by insertion of a 99Z neutral density filter into the beam to protect personnel. The radial position of the mirrors on

the blade was established by shimming the blade radially outward with Teflon

shims between full root and hub, then slowly rotating the blade through the

incident beams and tracing the path of the spot with a pencil across the top

surface. Cardboard templates were cut to match the arc in the blade surface

and chordwise distances of I0, 50 and 90% for the A row; lO, 50 and 85% for

the B row; 10, 40 and 85% for the C row; and lO and 90Z for the D row, were

marked out along this arc. The template was then used to locate the chordwise

position of the center of each mirror on the surface of the blade. A

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lcm x lcm Teflon block taped to the blade, supports the mirror epoxy mass

during the time the epoxy is hardening (fig. 10). 3mm (1/8 inch) diameter x

lr_m (0.04 inch) thick mirrors are supplied by Edmund Scientific Company.

Actual mounting of the mirror was achieved by moving the rotor until the

•.'." specified location is centered under a laser beam. A small bead of room temperature curing epoxy was placed on the bottom surface of the mirror and the

mirror was then set on to the blade. After the epoxy hardened, a smooth fairing of epoxy was built up around the mirror to provide additional strength.

This method of mounting the mirrors proved extremely effective and durable

throughout the test program and no mirrors were lost due to centrifugal or

vibratory forces.

Direct photographs of the blade tips to provide an independent displacement measurement was possible because of the availability of a hiRh intensity

short duration spark gap flash unit and the UTRC designed and fabricated digital phase shifter which operated from the I per rev and 60 per rev signals

available from the spin rig drive shaft. A simple calculation shows that at

maximum speed of 9,000 RPM, the blade tip will move only approximately 0.003

inches during the 1/4 _sec flash duration resulting in sharp, well-defined

photographs.

For the high speed tip photographs, a 12 inch (30.5cm) x 12 inch (30.5cm)

front surface mirror was placed at a 45 degree angle with its plane normal to

a radial plane centered on the blade Y-axis plane (fiRs. II and 12). A small

secondary lens assembly was located between the mirror and blades to bring the

hub pointer and reference mark to focus at the same radius as the blade tips.

The source of illumination is a I/40sec air gap spark unit, located outsid,,

the vacuum chamber triggered by-a UTRC designed digital phase controller

driven by l per rev and 60 per rev signals from the drive shaft. The phase

controller permits control of the trigRer signal to illuminate any point on

the circumference of the rotor.

The camera, a 35ram SLR, was mounted outside the vacuum chamber along side

the flash unit.

I• The blade mounted dynam B. icDynainmistcrumIennsttatruiomentn compr ationises two parts: the

[ piezoelectric crystals used to induce vibration in a desired mode, and resist tance strain gages to define blade response. Figure 13 shows the strain RaRe

and crystal locations, and Table III Rives the relationship between ".hestrain

gage locations and the corresponding NASTRAN grid number and coordinate.

Crystal location was based on bench test experiments to give good vibratory

response of the blades in their first five normal modes. Two lead zirconat_.-

_._ titanate crystals paralled electrically to increase force input were used to

i • excite each blade. The crystals, Type G1356 supplied by Piezo Electric

_-;_ Products were 1.00 x 0.5 x 0.010 inches. Development of the crystal excita-

_-! tion technique is described in reference 7. Strain RaRe locations were chosen
on the basis of analytical stress distributions derived from NASTRAH (ref. 3)

for the first five vibratory modes.

The two blades chosen to have the extensive instrumentation (blade S/N 2

with 15 strain gages, and blade S/N I0 with II mirrors) were selected on the

basis of their having average frequencies as measured on the bench.

Micro Measurements constantan loll EA-06-O62AP-120 single element strain

gages, and EA-O6-062RB-120 Rosettes were used in the program. Blade surfa.

preparation was in accordance with Micro _ieasurements recommended procedures

prior to bonding the gages with M Bond 6i0 adhesive. Because the blade itself

forms one leg of the crystal excitation circuit, a spot conductive adhesive

was used qlong with cnnucntlonal epoxy to attach the crystals.

¢ Blade Excitation, Data Acquisition Systems

A schematic of the overall blade excitation and data acquisition system,

is shown in Figure 14. The three leads from each strain gage (two si2nal and

an independent excitation lead for temperature compensation) were routed

through the center of the drive shaft and turbine to the 100 channel Electro

Tech slip ring rated at 6 m_ maximum noise at I00 ma current at 9,000 RPM.

Bridge completion was accomplished with precision resistors mounted in

terminal strips adjacent to the slip ring. Bridge excitation and signa,

conditioning made use of the front end portion of an A._nalogData R__ecording

System (ARES). This is a semi-portable sys:em for the automatic acquisition

of dynamic test data with oscillatory frequency rates from zero to 20 kHz. A

maximum of 28 analog signals can" be processed. Each channel incorporates

independent signal conditioning and amplification. The signal conditioners

are specifically designed for strain Rage type transducers and provide r,.gufated excitation up to lO volts. The amplifiers provide voltage a=plificatio.,

of I, lO, I00, or 1,000, and are each equipped with low pass signal filters

with roll off frequencies of 10Hz, 100Hz, IkHz, 10kHz, and 100kHz. Signal

monitoring can be achieved through a single channel selectable digital display

readout which includes RMS measurement capability for averaging dynamic

signals.

Data recording was by the computer controlled I_RC Aeromechanical

_ransient __LoggingSystem (ATLAS) which prepares, digitizes and records the

analog signal from the strain _ages. For the present tests, sampling rates

were chosen to record between 50 and 80 complete cycles of the mode of

interest. Reduction of the data is discussed more fully in the section on

test procedures (VII).

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Also shown in Figure 14 is a schematic of the controls for the

i.i piezoelectric crystal blade excitation system. The UTRC designed and

fabricated main control provides for independent level and phase control of

° the voltage to each of the five blades. This independent control of the phase

"" angle between blades permits the rotor to be driven in any given circumferential wave (nodal diameter) pattern, and allows arbitrary selection of the

direction of wave travel relative to the rotor. The control is driven with a

Hewlett Packard HP3311Asignal generator which allows fine frequency control

with external DCvoltage input. The five outputs are routed through the slip ring to the blade mounted crystals.

9

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VII. TEST PROCEDURE

A. Steady State Deflections

Prior to recording data from the surface mounted mirrors, the initial

positions of the spots on the marked screen were recorded by turning the rotor

by hand with the chamber evacuated and marking the reflections from each

mirror on the screen. A photograph of the marked screen was made and served

as the zero speed reference location for each mirror. The'rotor was then

accelerated, allowed to stabilize at each required speed, end a photograph of

the reflections was made. The exposure was chosen to give 10 to 20

repetitions of each reflection. Figure 15 shows a typical photograph of the

screen which also shows the scales needed for length calibration and a

repeating tachometer for measuring the speed. This procedure served well up

to a certain speed beyond which most of the reflections had passed outside the

field of the window and thus could not be recorded " Several attempts were

made to rebond the mirrors to the blades to permit greater range of travel but

the combination of blade bending, twisting angles, and the plane of the rotor

relative to the window resulted in spot deflections at 9,000 RPM which

exceeded the 12 inch diameter of the viewing window. To provide positive spot

identification and eliminate ambiguity from spot crossings on the still

photographs at increasing speeds, a real time video recording was made of a

slow acceleration, and from this a continuous tracing of each spot (fig. 16)

as a function of speed was prepared. Figure 16 shows the trajectories of the J

midchord tip mirror reflections from all five blades which represent a measure i

of how well the blades match each other in their twist. The observation that

OZ.for blade S/N I0 is larger than for the other four blades is attributed i

to the extra mass of the eleven mirrors and epoxy adhesive on that bla'de. The

data points shown in Figure 16 at even 1,000 RPM increments are for _t'

convenience in comparing deflections among the blades, the shape of each

curve, however, is determined by _ to I0 speed points. i

Data reduction was achieved by projecting the negatives on a microfiche

reader and measuring relative spot displacements, which were then simply

converted to angular displacements of the blade. Since the mirrors in general

are situated a distance away from the blade Y-axis there is coupling between

the measured Y and Z rotations. The curves for all the m:rror data are shown

in Appendix I, resolved into blade Y and Z coordinates and are thus directly

comparable to similar quantities calculated from NASTRAN.

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i To obtain photographs of the tips, the rotor was brought up to a given

speed and stroboscopically illuminated with a multiple flash strobotach

triggered by the once per rev signal from the drive shaft. A digital phase

- shifter was used to adjust the time of flash relative to the once per rev

,- pulse, thus the rotor could he "stopped" at any angular location. Each blade

" was lined up visually using the hub reference mark relative to the hub

pointer. When the correct alignment had been achieved, the strobotach was

removed from the circuit and replaced with the single pulse high intensity

Hicroflash 599-11 light source and driver. Recording was achieved by opening

the camera shutter, pulsing the flash unit and closing the shutter. In this

/./ manner, two independent photographs of each of the five blades were taken at

i/ each of six speeds.

Data reduction was accomplished by projecting the negatives onto vellum

at an overall magnification of approximately 4X. The position of the blade

leadin_ and trailing edges was marked as were the position horizontal and

vertical fixed reference lines. Blade deflections were determined by the

variations in position from thp reference marks.

It was determined that the circumferential, w, displacements are sub.iect

to significantly more scatter and error than the axialj u, displacements, and

rotations. Despite the availability of a reference at the hub, an error

in determining the hub position was magnified by the ratio of tip to hub radii

(a factor of approximately 3). Consequently the inherent scatter is

magnified. For tip twist and axial displacements, however, the tip photos

yielded satisfactory results.

!_. B. Dynamic Testing

!

T. Prior to the determination of vibratory characteristics of the assembly t

' at speed, the blades were individually characterized with the UTRC Genrad

Modal Analysis System. With the hub clamped nose down on a granite block,

[ each instrumented blade was mounted in its hub port and forced radially

outward with a bolt between base and huh to simulate centrifugal loading.

System output to force input ratio was recorded up to lkHz for each of the 27

i strain gages by means of an instrumented hammer.

i

!'' The instrumented hammer is generally used to excite a structure

! transiently for use in modal analysis systems which employ the FFT techniques

to determine modal parameters. This impulsive force technique utilizes short

transient force inputs (with corresponding broad-band spectra) to excltc all

the modes in the structure simultaneously. A force transducer is mounted on

the har_mer and the strain ga_es are located on the blades at the specified

_' locations. The structure is excited at a multiplicity of predetermined !.: locations using the hammer and the response is picked up by the strain ga_es.

The two transient time histories, i.e., force and response, are automatically
digitized and then Fourier transformed by a minicomputer to yield input and

output spectra. The resultant ratio of the output to input spectra is the

_ desired transfer function. By repeating this process at a number of points on

,': the structure, the mode shapes at individual resonant frequencies can be

; determined. The results from these tests yielded the modal amplitude,

frequency, and phase data for all the strain gages on all the blades, _ich

provide the basis for comparison with corresponding results at speed.

For tests at speed, the rotor was mounted in the vacuum spin rig, and

strain gages and crystals connected through the sllp ring to the data system

and excitation control respectively. During the initial functional check of

the system at low speed, it was determined that an excessive amount of crystal

excitation voltage was appearing on the strain gage channels, resulting in

unacceptable crosstalk. The source of this crosstalk is discussed belov.

During the process of routing the strain gage leadwires and crystal

excitation vires from the slip ring up through the turbine and prop fan

spindle, the small size of the spindle bore (3/8 inch diameter) precluded the

possibility of properly isolating or shielding the 81 strain gage wires and

the 5 crystal excitation leads. Consequently the crystal excitation wires

were embedded within the strain gage lead bundle, and are constrained to 3/8 i

inch diameter for a length of approximately 30 inches. This arrangement

resulted in unacceptably high crosstalk voltages appearing on the strain gage

signal leads. Thus, the close proximity of the excitation and strain leads

over a significant length, lack of fsolation of shielding, the relatively high I

impedance of the strain gage circuit (120 fl), and high crystal excitation I

voltages, generally between 50 and 100 volts peak to peak were identified as

the important factors contributing to this nroblem. Further, the crosswalk is +

sinusoidal at or very close to the response frequencies of the blades and thus i

is not subject to filtering. The crosstalk was evaluated by driving the _'

crystals at frequencies away from blade resonant frequencies so that physical

blade response would be low and the signals avpearing on the strain gage

channels represent actual capacitively coupled crystal excitation. The

effects of the crosstalk were by-passed by recording the decay of free vibrations and reducing data by a time domain analysis as outlined in Appendix III,

and reference 8. To obtain a data record with the rig stabilized at a

specified speed, the crystals were energized at a specified amplitude and

interblade phase angle. To find the system frequency, a responsive strain

gage channel was monitored visually on an oscilloscope as the excitation

oscillator was swept slowly around the frequency of interest. Away fron the

resonant frequency the monitor signal was a constant amplitude sinusold

representing the crosstalk amplitude, as resonance was approached the

amplitude increased to a maximum. When it was visually determined that the

blade response was at a maximum, the excitation was switched off and data

recording started simultaneously. This method proved satisfactory for data

records in modes l, 2, 4, and 5, but the 3rd mode proved to be very difficult

•" 12 i
._..,_._,__ _,___'_._ ...........................

bl

L .

to excite. Table ZV shows the array of speed, modes and interblade phase

angle for which records were made. Vibratory testing was not carried out at

speeds above 7,000 RPM because the earlier calculations had indicated a

potential I00 ksl steady stress at the airfoil trailing edge. The combination

,- of this high steady stress with vibratory stress suggested the risk of failure

to be unacceptably high. >

t"

t

L
t

........................ : ''i

!

;

VIII.

I DISCUSSION

A. SteadyStateDeflections

The influence of the centrifugal field on the steady state blade twist

for the SR-5 is summarized in _igures 17, and 18. Figure 17 shows the

spanwise distribution of airfoil twist about the Y (radial) axis obtained from

measurements at the midchord row o£ mirrors at three spanwise locations (A2,

B2, C2). It _s seen that the twist angle increases unformly with span up to

about 80Z from which point it decreases out to the tip. The interruption in

the 8.000 RPH curve is caused by the fact that the spots reflected from the B

row of mirrors were outside the range of the viewing window and consequently

could not be photographed. Also shown ie Figure 17 are the results of NASTRAN

calculations at 7,000 RPH. NASTRANresults are in agreement to within 5% of

the mirror data up to this spanwise position of maximum twist angle beyond

wthehische data. NASTRANdoes not predict the decrease in twist clearly indicated by

Figure 18 compares the difference in twist angle from leading to trailln_

edge along the span at 7,000 RPM. NASTRAN results at similar blade 1ocatlons

are also shown on the figure. It is seen that over most of the span the

trailing edge twists much more than the leading edge resulting in the

significant decrease in airfoil camber shown. Near the root and tip the sense

of the camber change is reversed leading to a small camber increase particularly at the tip. NASTRAN results show a similar uncambering characteristic

with span which agrees closely with the measured values up to about 60% span

above which NASTRAN indicates larger uncamber than was measured. For the

transonic Mach numbers at which the blade operates, it may be anticipated that

(a) similar changes in airfoil camber will have a significant effect on I_'

overall rotor performance and (b) a precise knowledge of the blade twist and !

uncamber will be required to predict the aerodynamics, i

Plots of all the individual mirror data _y and OZ' corrected to NASTRAN axis system are given in Appendix I.

An attempt was made to obtain the blade deflection u (axial) by integrating the measured _y and @Z slopes over the surface of the blade. An

expression for differential u deflection was written in terms of the O.yand

_'zslopes. The 0 X term is assumed zero because the plane of the mirrors'on

the blades are perpendicular to the X axis consequently insensitive to

rotations about this axis. It was further assumed that u is independent of

path. To facilitate integration, the data was fitted using a least squares

fit with a two-dimensional polynomial expression in Y and Z.

14
Integration of these expressions along several straight line paths gave

' rise to deflection values that were strongly path dependent and were much

larger in magnitude than would normally be acceptable. " It was concluded that

this method of calculation of displacements is not satisfactory. Among the

_" alternate methods examined, the followlnR was chosen.

It was decided to take strobe photos of the tip and measure tiV displacement more directly. Figure 19 (a superposition of two photographs of the tip'

. of blade number 5 taken at 1,600 and q,000 RPM) shows clearly_the large

centrifugal twists and displacement that can occur. In the figure, the lower

image o_ the tip (painted white to enhance visibility) was taken at 1,600 RPM

and the upper image taken at 9,000 RPM.

A careful review of the data indicated that a single photographic image

of the tip does not contain adequate information for twist angle to be

compared directly with corresponding laser/mirror twist data. The tip chord

has projections on the X, Y and Z axes, consequently, centrifugal deformation

of the blade results in projection of rotation on all the axes. The camera /

/ records only one of these projections which is related to _, and therefore

will not admit to quantitative comparison because the other components of

, rotation which couple with _y cannot be recorded on a sinRle ohotographic

_.. plane. A more complete description of this effect is given in Appendix II.

Linear displacement measurements, however, are comparable because the

: displacement is in the same plane as the photographic image, and the u (axial)

displacement characteristics for the leading and trailing edge tip section are

i shown in Figure 20 as a function of speed. The points plotted represent an

average of two ohotographs from each of four blades with the spread of data

indicated by the vertical bars. The four blades used for averaging the data

were Serial Numbers I, 2, 5 and 8. Blade number I0 was not included in the

averaging because it had a different mass distribution from the other blades t

[" caused by the full array of II mirrors bonded to its surface. Results Fro_

I NASTRAN obtained for 7,000 RPM show excellent agreement with the averaged

! measured values. Correlation of w (tangential) deflections by means of the

tip photos has met with little success. It may be recalled that the correctlon of small differences in timing the strobe flash was done by means of a

_'_ reference mark at the hub. An error in applying the timing correction

r measured at the hub to a physical blade deflected positional the tip is

•"_" magnified by the ratio of tip radius to hub radius (a factor of approximately

i. 3). This correction is of the same order as the blade w deflection,

consequently the scatter in the photographic w measurements is the same size

i as the w displacements.
B. Vibratory Tests

A summary of the individual blade frequencies measured from the bench

impact tests including the effects of instrumentation is given in Table V.

The mode.shape data, amplitude, and phase, for blade number 2 which had the

extensive array of strain gages, is shown in Figures 22 through 26. Also

shown on figures 22 through 25 are some deflection mode shape holograms

supplied by NASA from their bench tests. As discussed in Section VII, the

piezoelectric crystal excitation system was used to excite the five blades of

the SR-5 rotor system both individually and in a variety of nodal diameter

patterns for the first five blade modes. However, crosstalk between crystal

excitation voltage and strain gage signals prevented acquisition of steady

state frequency response data. Therefore, vibratory decay data was recorded

and analyzed through time domain procedures. This approach has proven to be

capable of providing required dynamic information for the assembly.

The specific rotor characteristics which were evaluated include:

I. Frequency vs. speed for the first five blade modes

2. Extent and characteristics oF mechanical coupling amon_ the blades

and the resulting coupled modes

3. Blade stress mode shape response with speed for the first five blade

modes.

Results obtained from reducing the vibratory tests are presented and I

discussed below• t

Frequency Response of the Rotor - The variation of the vibratory natural

frequencies of the assembly with speed is shown in Figure 21. AlthouRh i ,

excitation was imposed on all the blades at a variety of prescribed nodal ;_

diameter patterns in both forward and backward traveling waves, amplitude t.

decay signatures generally consist of a mixture of waves.

At several speeds and modes, pairs of frequencies very close together

were observed as shown in Figure 21. In these data, the upper frequency

represents a mode in which all the blades are exactly in phase in an

"umbrella" mode, and the lower frequency exhibits a mixed nodal diameter

pattern. While strong response was noted in modes one, two, four, and five,

the third mode proved to be difficult to excite at speeds above 4,000 RPM.

Therefore, little data could be obtained close to the third mode frequency.

This characteristic was also observed in the bench tests, in which the third

mode response was always significantly less than the response in the other

four modes. Examiua_ion of the mode shaves in the fourth and fifth modes

shows that there is an apparent crossover of modal frequencies. This will be

discussed further in Section C.

16
Figure 21 shows results from NASTRANa, blade alone frequency calculation, for the frequency of the first five modes as a function of speed.

5uperpOsed on the same figure are the test data which represent the

frequencies of system modes measured at selected speeds. It is emphasized

that the test data shown in Figure 21 represent system modes and therefore are

not directly comparable with the blade alone calculations shown. The

frequency of the system modes shown are avproximately 10_ higher than the

individual blade above frequencies for the first two modes. This is possibly

due to the predominance of inertial effects in the coupling mechanism.

All of the experimental modes shown on Figure 21 represent rotor coupled

modes; i.e., the response frequency of each blade in the rotor is the same,

and there is a fixed interblade phase angle between them. The frequency

spread among blades due to normal manufacturing tolerances is shown along the

zero speed axis as measured from bench tests. Whether one blade of the

assembly or the complete assembly was subjected to forced vibration, the

entire assembly responded indicatin_ a significant level of mechanical

coupling among the blades. Attempts to relate the nodal diameter patterns of

the response with the nodal pattern of the excitation show that they are not

simply related because the response modes contain contributions from many

harmonics. It is noteworthy, however, that the various combinations of nodal

diameters show Small differences in frequency or mode shape.

The excitation of the assembly included both single blade as well as all

blades at 0, 1, and 2 nodal diameters in forward and backward traveling waves.

Decay patterns were characterized by either strong umbrella mode response

and/or a mixture of the other patterns. Tables VI through IX compare the

relative response amplitude of the waves for different patterns of excitation

including the excitation where only a single blade was driven. As observed

earlier, examination of these tables shows no consistent relationshlp between

the pattern of excitation and correspondent patterns of response. A possible

explanation for this lack of traveling wave correlation, is that the transient r,_

force induced by switching off the excitation induces a mixture of traveling

waves. The specific mixture is related to the timing of the transient during

the cycle. The detailed characteristics shown for the first mode are typical

of the higher modes also. It is interesting to note, however, that when the

umbrella mode is the major constituent of the rotor response, the decay frequency is approximately 9_ higher than those cases where the response contains

other nodal diameter patterns.

These results are based on time domain analysis of the slgnals from three

strain gages located on each of the five blades of the rotor, all of which are

responding at a constant frequency, la order to verify the strength of the

coupling, it is instructive to examine the frequency content in the response

17
by performing time domain analyses of individual decays from the three strain

gages located on each of the •blades. Table X compares system mode frequencies

as calculated by comparing the three strain ga_es at correspondin_ locations

on each of the five blades, with the frequency calculated for each of the

blades independently using the outvur of the same three strain gages. The

results shown on Table X are for Ist, 2nd, 4th, and 5th system modes at 7,000

RPHand are typical. Table X also shows underneath the frequency of the blade

for that mode as measured on the bench. It can be seen that the coupled mode

frequency spread among the blades is much less than would be seen if the

blades were not coupled through the hub.

C. Blade Strain _ode Shape

The variation in blade strain distribution for each mode and speed was

also evaluated_ In order to clarify the individual blade strain mode shapes,

the information from the twelve active strain gages on blade number 2 is displayed as shown on Figure 22. In this figure, an outline cf the pressure and

suction surface of the blade is shown along with the location and orientation I

of each of the strain gages. Strain gage numbers l and 5 were not included in

the da_a recording because their output during the bench test characterization

was less than 5Z of the maximum reading strain gage for all five modes of

vibration, so it was felt that they would contribute little to mode

identification. Below the blade outline is a bar chart where each bar

represents the output from the corresponding numbered gage on the blade. The

_eight of the bar represents strain amplitude normalized to the maximum (which i

varies fordifferent modes) and the position above or below the axis shows I

whether the phase angle relative to gage number 2 is 0 or 180 degrees.

I

I

I

Figures 22 through 26 are the results of the modal analysis evaluation of _ .

the zero RPM bench impact tests. For the first four bench vibration modes,

NASA acquired physical displacement mode shape data by means of holograms i

which are included as insets on Figures 22 through 25. This data allows !

qualitative comparison of physical deflection with local strain.

Results from time domain analyses of blade strain mode shape at s_eeds of

4,000, 5,000, 6,000 and 7,000 RPM, are shown on Figures 27 through 31, where

rotational symbols have been superimposed on the bench test results to

facilitate comparison.

Two groups of four symbols have been superimposed on each "bar" to show

blade mode response for the two characteristic system modes with zero interblade phase angle (umbrella mode) having solid symbols, and the nonzero interblade phase (mixed nodal diameters) angle having open symbols. The speed at

- _nich the data were recorded is shown by the shape of the symbols. The

displays are complete for the first and second modes, but only partial for the

higher modes because there were fewer of these data with sufficiently high

confidence factors. The third mode is particularly sparse, because'of the

_ difficulty in exciting it at speeds over 4,000 RPM.

18
Examination of the change of the mode shapes with respect to speed leads

to the following observations.

a) The system mode with predominantly zero interhlade phase angle

(umbrella mode) and modes with nonzero interblade phase angle (mixed

nodal diameters) show virtually no difference in blade strain mode

shape despite the frequency difference on the order of 9%.

b) The modal distribution of strain from the zero RPH measurements is

only an in_;ial screen for modal identification because the data at

speed may show a substantial difference and may reflect changes in

blade root constraint.

c) The highest frequency mode at speeds above 4,000 RPH has a strain

distribution resembling that of the fourth mode at zero RPR (fig.

30).

d) The fourth _ode at speeds above 4,000 RPM has a strain distribution

resemblinthat g of 5thmodeat zeroRPM (fig.31).

e) The third mode was difficult to excite at speeds above 4,000 RPM,

consequently changes in strain distribution with speed could not be

recorded.

The vibratory stresses at the strain gage positions calculated from

NASTRAN, are also used for comparison with the corresponding experimental

blade measurements. With the computed values of _x" oy, Txy for each finite

element, the stress component oriented in the strain gage d_rection can be

calculated, i.e.,

_ = -- + -- cos 2_ + sin 28 2 2 _xy

These values were averaged arithmetically for the elements immediately

adjacent to the nodal point identified with a particular strain _age. These

results are shown superimposed on the bench test results in Figures 32 through

36.
The first two modes showed satisfactory correspondence between experimental bench test mode shapes and the NASTRAR predictions at both zero and

7,000 RPH. The third NASTRANmode, in contrast, showed no relationship to any

of the three higher bench modes. The fourth bench test mode showed significant similarity to the fifth mode of the RASTRANpredictions. The fifth

bench test mode and the fourth NASTRANmodes showed a limited similarity to

each other.

The NASTRANmodel used a mesh size which _ave undesirably large variations in o8 among the elements surrounding a nodal point, _n the higher

modes. For modes above the lowest two, a locally refined _rld might be used

to advantage.
i.:!

I IX. MAJOR CONCLUSIONSAND RECO_,_MENDATIONS

,,

Based on (a) the test data obtained by testing the five blade configuration of the SR-5 assembly, and (b) the NASTRAN analytical results that were

made available by NASA/LeRC, the following major conclusions can be drawn.

1. Centrifugal loads acting on the assembly cause large reductions in

airfoil camber over most of the blade surface.

2. Maximumtwist due to centrifugal loads occurs inboard of the tip at

approximately 80% span. (

3. For the first five modes of vibration,the rotor respondsas a system

with all blades vibrating at the same frequency.

4. Blade strain mode shapes exhibit small changes between &,000 and

7,000 RPM for the first five modes of vibration.

_-., 5. NASTRAN blade alone frequencies generally agree to within I0% of the

"_ measured system mode frequencies..

6. NASTRAN calculation of blade tip axial deflection in the centrlfugal

field agrees with the measured values.

7. Significant differences exist between resu!ts calculated from NASTRAN

and corresponding measurements for twist and uncamber distribution.

8. Significan_ differences exist between results calculated from NASTRAN

and corresponding measurements of vibratory stress distributions at

both zero and 7,000 RPM. The biggest discrepancy occurs for the 3rd,

4th, and 5th modes of vibration.

9. Mechanical coupling among the blades can arise due to either the

inertia of the hub and/or the elasticity of the hub and pitch change

mechanism. The relative strengths of these contributions need to be

assessed.

Ii " I0. The major conclusions in regard to the modal characteristics of the

SR-5 assembly were drawn from analysis of vibration decay data.

" Further confirmation of these conclusions may be needed through data

obtained from measurements of frequency response characteristics.

I1. The added mass of the blade mounted mizrors is apparent in the

_ centrifugal deflection measurements.

.3

1

_" 21
X. REFERENCES

0

. _ I. Dugan, J. F._ Hiller, B. A., Grabear, J. J., Sagerser, D. A.: The NASA

.

,_ High Speed Turboprop Program. National Aeronautics and Space Administration, NASA T_ 81561, October 1980.

2. Hehmed, O., Kaza, K. R. V., Lubomski, J. F., Kielb, R. E.: Bending

' Torsion Flutter of a Highly Swept Advanced Turboprop. NASA TH 82975, October 1982.

3. La_rence, C._ Kielb, R.: Finite Element Analysis o_ an Adwnced TurboProp Blade. NASA T8 (To be published).

i 4. Hartman, E. P., D. Biermann: Torsional and Bending Deflection of Full

. Scale Aluminum Alloy Propeller Blades Under Normal Operating Conditions,

NACA Report 644, Langley HemoriaI Aeronautical Laboratory, January 1938.

,i_ 5. Stargardter, H.: Optical Determination of Rotating Fan Blade Deflectlons. Journal of Engineering for Power, Aprll 1977, pp. 204-209.

_ 6. Stargardter, H.: U. S. Patent 4,080,823: Vibration Measurement.

:, 7. Srinivasan, A. V., Cuffs, D. G.: Basic Study of Bladed Disk Structural

;, Response. United Technologles Research Center, AFWAL TR-83-2075

November 1983. '

_! 8. Ibraham, S R. Mikulcik, E C.: A Method for the Direct Identification

: of Vibration Parameters from the Free Response, Shock and Vibration

:# Bulletin, Vol. 47, Part 4, pp. 183-198, September 1977

9. Brand L.: Vector and Tensor Analysis. Niley, New York 1947.

22
TABLE I

p_

Number of Blades in Rotor: 5 (10 in prototype)

p_Fip 12.1 in (31 cm)

RHub 2.83 in (7.19 cm)

t/bRoot .I05

t/bTip .018

Mechanical Design RPH 9000

Tip Speed at Design 950 ft/sec (290 m/sec)

/ i

_. Material Ti 6-4

7.

Reference angle at 3/4 radit,s 58.5 deg relative to tangential plane

!. Max sweep back angle at tip 63 degrees

F_

LE Radius Tip (nominal) .003 in (.0076 cm)

LE Radius Root (nominal) .0614 in (.156 cm)

> k

23

#

..... f
/t

L__,._L%?_.. "!-,_.._,... t:_'_:.'--'l. ,. ; _,. ":." ........ .. , _'.. _ r ..................

._o

, o , |

1

!

!

I

Table11"MomentWeightResults.

I

i

BLADE BLADE MOMENT

NUMBER WEIGHT WEIGHT

gms gmcm

5 387.6 5009.6

1 3889 5051.8 '

2 392,5 5062.6

8 3960 5153,3

10 399,2 5245.7

INCLUDING INSTRUMENTATION

BLADE I

J

BLADE 10

8LADE

BLADE 5 BLADE 8

ORDER OF BLADESIN ROTOR

VIEW LOOKING DOWN STREAM

84-4--7-8

24 /.7,
" ,°,

t

, !

• k..! PROP-FAN STRAIN GAGELOCATION

t

.. Orien.

Gage No. Surface Gage Type Grid No. X Y Z of Grid

8,9,10 Pressure Rosette 317 0.2403 6.9958 -0.0128 0-90-45°

11 Pressure Uniaxial 155 -1.0952 9.4786 0.5885 Parallel

to LE

12 Pressure Uniaxial 206 0.5046 11.0547 -0.8096 Parallel

Between to LE

67 & 78

• 13 Pressure Uniaxial 202 1.2244 11.6501 -1.5318 - LE

'' Between i

_ 23-_

i 14 Pressure Uniaxial 176 1.8833 9.2321 -1.1797 Parallel I.

to TE

, 7 Suction Uniaxlal 105 1.1116 10.5534 -I.1412 40* to

i'

r YZ Plane

; 4,5,6 Suction Rosette 150 0.8160 9.7245 -0.7130 0-90-45"

:" 1,2,3 Suction Rosette 316 -0.1186 6.9958 0.1698 0-90-45°

15 In Fillet Uniaxial 435 0.5397 3.1003 -0.1820
TABLEIV

Blade Interblade Blade Interblade

Speed Mode Excited Phase Angle Speed Mode Excited Phase Angle

4000 #2 6000 1 #2

All 0 All 0

l +72 l +72

+144 +144

-144 -144

-72 -72

2 All 0 2 #2

3 #2 All 0

All 0 | +72

l +72 J+144

+144 -144

-144 -72

-72 3 #2

4 #2 All 0

5 #2 | +72

All 0 1 +144

l +72 -144

+144 -72

-144 4 #2

-72 All 0

5000 #2 5 #2

All 0 All 0

l +72 +72

_ +144 +144 I

_'i. -144 -144 i

-72 -72

2 #2 7000 #2 i

All 0 All 0

All 0 +144 '

[. | +72 -144

; 1 +144 -72 _, -144 2 #2

-72 All 0

4 #2 +72

' 5 #2 +144

All 0 -144

+72 -72

+144 3 #2

-144 All 0

-72 l +72

r +144

-144

-72

4 #2

5 #2

All 0

J +72

+144

-144

-72

26 I

,:f
6

TABLE V

BENCHTEST RESULTS

Summary of Individual Blade Frequency

Including Instrumentation

BLADE SERIAL NUMBER

MODE 1 2* 8 5 lO**

_ w._-,=...=-

i

.

":i _l II0 Mz 112 Hz 109 Hz 113 Hz 112 Hz

_ .==._.-=-==.---

[ 2 274 Hz 281Hz 277 Hz 283 Hz 277 Hz

_:'! 495 Mz 492 Hz 462 _z

3 472 Hz 476 Hz _ ___ ._

I:I ---- 594 Hz

_. 4 596 Hz 604 Hz 607 Nz 617 Hz

_i. 64i Hz 649 Mz 646 Hz

5 633 Hz 638 Hz

!.

f

;. * 15 Strain Gages on Blade

I _ II Mirrors on Blade

L

t

t

[.f
TABLE Vl

NODAL DIAMETER RESPONSE PATTERN DURING

DECAYVS. TYPEOF EXCITATION

4,000 RPH

First Mode

Strain Cage No. 12 on All Blades

EXCITATION PATTERN

Strength of Single _ __

Harmonic Present Blade 0 Nodal Dia. 1 Nodal D[a. 2 Nodal Dia. 2 Nodal D_a. I Nodal D_a.

During Decay Excitation (umbrella) Forward Forward Backward Backward

0 Nodal Dis. 1.00 1.00 15 .15

(umbrelLa) " .10 .10

For 1 Nward odal Dia. .25 .25 .65 "65 •I0 .65

2 Nodal D_a. .20 .20 .60 .75 1.00 Forward .70

2Backw Nodaalrd Dia. .20 .20 1.00 1.00 .45 1.00

I Nodal Dia. .30 .30 .35 .75 .60 Backward .40

System

Frequency 148.23 Hz 148.39 Hz 135.01Hz 135.10 Rz 134.56 Hz 134.86 Nz
TABLE VII

NODAL DIAMETERRESPONSEPATTERNDURING

DECAYVS. TYPE OF EXCITATION

5,000 RPH J

< First Mode

Strain Gage No. 12 on All Blades

EXCITATION PATTERN

Strength of Single

Harmonic Present Blade 0 Nodal Dia. I Nodal Dia. 2 Nodal Dia. 2 Nodal Dia. I Nodal Dia.

During Decay Excitation (umbrella) Forward Forward Backward Backward

0 Nodal Dia. .35 .35 .30 .35 .35 .40

(umbrella) ]

I Nodal Dia. .70 .75 .65 .75 .70 .60

Forward

2 Nodal Dia. .85 .30 .65 .85 .95 .95

Forward

2 Nodal Dia. 1.00 .40 l.O0 1.00 1.00 1.00

Backward

I Nodal Dia. .85 1.00 .60 .95 .80 .60 ,

Backward

System

Frequency 145.82 Hz 145.97 Hz 145.72 llz 145.76 Hz 144.81Hz 145.73 Hz
TABLEVIII

NODALDIAMETERRESPONSE PATTERNDURING

DECAYVS. TYPE OF EXCITATION

61000 RPM

First Mode

Strain Cage No. 12 on All Blades

EXCITATION PATTERN

Strength of Single

Harmonic Present Blade 0 Nodal Dia. I Nodal Dia. 2 Nodal Dia. 2 Nodal Dia. 1 Nodal Dia.

During Decay Excitation (umbrella) Forward Forward Backward Backward

0 Nodal Dia. 1.00 1.00 .40 .15 No Data .

(umbrella) .15

0

1 Nodal D_a. 0 0 .65 .30 Forward .40

2 Nodal Dia. .I0 .I0 ,25 .90

Forward 1.00

2 Nodal Dia. .05 .05 .30 1.00 '

Backward .95 ;

l

I Nodal Ola. .05 .05 1.00 .45

Backward _ .35 !

System Response

Frequency 173.99 Hz 174.43 Hz 158.8 Hz 157.18 Hz 157.71Hz
s

/

s'

/

TABLE IX

NODAL DIAMETER RESPONSE PATTERN DURING

DECAY VS. TYPE OF EXCITATION

7,000 RPH

First Strain ModGaege No. 12 on All Blades r_!

EXCITATI PATTE.N ON i' ' i/!

I/. t

Strength of Single _.i

Harmonic Present Blade 0 Nodal Dia. I Nodal Dia. 2 Nodal Dia. 2 Nodal Dia. I Nodal Dia. !

During Decay Excitation (umbrella) Forward Forward Backward Backward i

I"

0 Nodal Dia. 0 1.00 .05 .15 .I0 0 :

(umbrella)

I Nodal Dia. 1.00 0 1.00 .25 .I0 .60

Forward

=,

2 Nodal Dia. .20 .05 .15 .85 1.00 .40 I

Forward i "

i

2 Nodal Dia. .20 .05 .20 1.00 .45 .I0 II

Backward !.

I Nodal Dia. .45 .05 .45 .35 .30 1.00

Backward

System Freq.

of Delay 172.33 Hz 188.31Hz 173.39 Hz 170.70 Hz 170.42 Hz 172.03 Nz

\
I , I

TABLE X

COMPARISON OF SYSTEM FREQUENCY NITH BLADE FREQUENCY _

AT THE SAME TEST POINT

System Mode Blade 1 Blade 2 Freq. Blade 8 Made 5 Blade 10

Frequency Freq. All Gages/2 Gages Freq. Freq. Freq.

First Mode 7,000 RPM

Excite Single Blade 172.4 Hz 172.3 Hz 172.5/172.5 Hz 172.1 Hz 172.4 Hz 172.3 Hz ,-

First Mode 0 RPM J

Bench Test 110 Hz ll2 Hz 109 Hz 113 Hz I12 IIz

Second Mode 7,000 RPM

Excite Single Blade 291.8 Hz 292.1Hz 292 Hz 291.5 Hz 305 Hz* 291.7 Hz I

Second Mode 0 RIM I

• Bench Test 274 Hz 281Hz 277 Hz 283 Hz 277 Hz ]

;

Excite All Blades _ = 144' 620.5 Hz 620.4 Hz 621.0/620.8 Hz 62i.2 Hz 623.3 H= 619.9 Hz t

Fourth Mode 0 RPM

Bench Test 596 IIz 604 Hz 607 Hz I 617 Hz 594 Hz

Fifth Mode 7,000 RPM

Excite All Blades q):72" 711.2 Hz 711.7 Hz 710.7/712.0 Hz 712.9 Hz 704 Hz* 712.7 Hz

Fifth Mode 0 RIM

Bench Test 633 Hz 638 Hz 641Hz 649 Hz 646 Hz

* Analysis showed low confidence factor
ORIGINAL.PAGEi._;

.I; OFPOORQUALITY J

r° • •

' Fig. 1 UTRC Centrifugal Testing Facility

r

!.

t. "

,.'_i

_..!

_;2 82-12--73--27

_ 33
I.. i PROPFAN !

AND HUB

ADAPTOR

CHAMBER

MAIN SHAFT BEARINGS

SQUEEZE FILM

DAMPER

DRIVE SHAFT

b r-- l_.j _ FLEXIBLECOUPLING J

!_:.i. AIR TURBINE

'- ! LE COUPLING

r

SLIP RING i

t,,

lr-

_". _ Fig.2 UTRCSpinRigDriveSystem

- _

/"

84--4--7--9

34
PITCH ANGL

E LOCKING PIN

TA GEAR

II

GEARRING

GEAR

_J_SECTOR

ON BLADE SHANK

• SECTION AA

CENTRIFUGAL

I RETENTION

I

A

Fig.3BladeRastralnt.: II
. -.--.----- - '---·-·_i._-:~.~...-__ r.-_ _~ ... • " _

... ~. n,:,'r"'~'·.i'~·"'··~~P'· ...... - .

Fig. 4 Photograph of Instrumented SR5 Assembly in UTRC Spin Rig

'"l>

I

..

I

"I

'"

0

::c w

c,

."

Gl

fT'i

:1".

. .
............. o.........

THRUST

TE

- : i- /

'\ o '_ESURFACE

. , FLOW / (FACE)

' _ / =€,z

SUCTION SURFACE _

TIP-TO-HUBVIEW
\

O0

.0

2

- -,- SUCTION SURFACE

.,.;,_ Fig. 6 NASTRAN Grid;Breakup of SR5 Blade

;. e_.

_I_!_. 38
I

t~C3 I

,.

t-

.' . .

f

•

rI

TIP STN 121 In

115 in. RAD

90% 500~

A3

STN 0

•

B2

50%

... ......-, -- _ ......

BLADE SIN 10: ALL LOCATIONS

OTHERS: LOCATION A2 ONLY

10%

BLADE CAMBER SIDE

I

9.5 in. RAD

....- :

Fig. 7 SR·5 Modol Prop-Fan Blade Mirror Locations

84-4-7-12

39
CAMERA

, , TRANSLUCENTSCREEN

;PLIT'rlNG

MIRRI :iS

FULL 50% 30% REFLECTIVITY. 2 MW LASER

°

WIN )W"___._ ": I _'--_ I I !

r I I \

I

• I 11 II CHVACUUM AMBER

b

I

, r "_ K" ( I

11

I

M i

L Fig.8 Schematicof LaserMirrorSet.UpforBladeDeflectionMoasuromont o

. 4

N _ .
ORIGIHAI.PAQE IS

Fig. 9 A Close.Up Photograph of Optical Bench

84--4--7 --5

I _
e

DIRECTION OF ROTATION

3ram DIA FRONT

SURFACE MIRROR

TEFLONBLOCK

TAPEDTOBLADE

EPOXY ADHESIVE i

i

!

BLADESECTION

Fig. 10 Scheme for BondingMirrorsto Blade

:lb

84--4--7-32

.i 42

_ r
- t Ii

F

?

F HIGH INTENSITY

STROBE LIGHT _,,

P

SPIN RIG VACUUM CHAMBER i

45 ° FRONT SU

PLANE MIRROR PROP FAN ROTOR HUB

:: \

\

.o_ o , \

t , .

I i • '

SECON'OEARNSY q" L

ASSY FIxEmo_NTER oF .. ROTATION

Fig. 11 Schematic of Tip Photograph Sot Up

OI

I

I

..J

_1
\

\

\

r1Il

I

I

"I

(j

Fig. 12 Photograph of 45° Mirror-Tip Photo setup

,.'.,.

I

"

. ,-, !. • I

.. '" ., \...
l_" "_.'_'I_"r'_ _'i"rr_'_"_" _" "_ I ..... " .....

i

PRESSURESURFACE SUCTION SURFACE

O3

f o2 ol

10 NOTE: BLADE S/N2 GAGE SHOWN

, •L1._n . V09 OGATHER GES F3.O1UR2. 14BLADONLYES HAVE

!

CRYSTALLOCATION

(ALL FIVE BLADES)

d

" !

b,

| . I

,., _.- [ - ------

Fig.13 SR5 PropFan StrainGageSchematic o
HI-SPEEDRIG

CRYSTAL 1 i

10 "'ATLAS"

DATA SYSTEM CH #I TRIGGER

STRAIN GAGE _ _

° I i!! ,

8 "ARES" I

| ,

TRIGGER i

@ CHANNEL O

"_ _ SELECT BOX

COUPLED

OUTPUT

SHAFT 2G CHANNELS I SCOPE

ASSY.

% 'l AC DIG.

VOLTMETER

SG CABLES

2S6 x FREQ J

I INPUT

CRYSTAL

S-CABLES CONTROL HP 331 IA

SYSTEM GENERATOR

"= O5--CHANN 100VELAMSS t

0SYNC -- 360_" _ DC-EXT FINEADJ. .FREQ.

J HPSS32A J OUT =. COUNTER I

I

I

- Fig. 14 Diagram of Excitation System, Data Acquisition and Recording System
,

i

l' ·1

[,' I

~'" I tc I

t

... ,

t

j"

t

I·

!

i,

I.

;

i

I

I

i

,

I

, _I

~.- ,.' f-",

t _ I

~>~: b" t:' ••,

ORIG'NAl PAGE IS

OF POOR QUALITY

.Fig. 15 Photograph of Spots Reflected from Blade Mounted Mirrors

84-4-7-4
R _ "_'.,_ ,_1_ _ I"'_'_._ z_ "

Oy(TWIST)RAD iI_

0.01 0.02 0.03 0.0'4 0.05 0.06 0.07 0.08 0.09 0.1( _'_o

I I I I I I I I I

V BLADE1 I

-O.Ol- n BLADE2

_=,BL,'_DE8

0 BLADE5

O BLADEI0

-0.02 -

a

,<

rr

t

-0.03-

z

LU

N

"0.04--

I

-0.05 -

-0.06 5000 RPM 7000 RPM 8000 RPM

L

,.I , Fig. 16 SR5 Steady State Bending (0Z)and Twist (0y) at Midchord Tip

o_
•1_._..... ",1=_ _._ ...... ..... ..

, ,:;

, I

o.

A

" 0.12

C2 B2 A2

I I I I

0.1 0 -- 7000 RPM

NASTRAN --_ _"'"-" _'

. /L BOO0 RPM

"_:" 0.08-

:. //

', _ // z

PM

tr O.Oeb I

>.

I 0.04-

_:.

_" O TIP PHOTO DATA 5000 RPM

I 0.02-- CORRECTEDFOR

• PROJECTIONGEOMETRY O-"

€

--_ _ NASTRAN 7000 RPM

3000 RPM

' ! I I I I I I

• 0 30 40 50 60 70 80 90 _00

, PERCENT RADIUS

l I I I

• 3.75 7.0 9.5 11.5

RADIUS -- in.

r Fig.17 BladeTwistOyvs % Radius

; ,ob=

._...

i"%,"

_; -__ . " B4--4--7--14
Fig.18 Blade UncambervsSpanat 7000RPM

- t

t

I

. t

!.-_!

: u,l_

_ _ 84--4-7--13

,.. 50
i1

.

i

, ... ..

aoe ••44 ..fIIZ1JF;I'JI

:.. :~~. ',~ ..!.....1 -' .. ,- .. ;' ./.. --.---- ---... ....~.~-~--......... ;XU oJ ..... _. We.!!.......

IIIlI

F· ,'2.-•h :q::::;p;r ..

Fig. 19 Tip Photos- Superposition of 9000 RPM (Upper) on 1680 RPM (Lower)

IfI•I

..... I

'"

;jIiIIII11!

VI

,

00

,,:tj

A

~C)

i O~ 1

~rI

0."

!

c>f

>C)

,

r- tr1

I ~(i; I

..
IL'.

t,

AVERAGEOF BLADESt, 2, 8, 5

0.06

.°-,_ ," , 0.04

t. • '

, 0.02 #

1

: 0

.0.02

-0.04 L.E.

.0.06

-0.08 -

I:::

'. = -0.10 -

p.-

Z

i' Lu

:_ -0.12 -

l Ill

<_ .0.14 -- a..

.J ,0.16 -

_<

•0.18 --

•0.20 - r.E. ,

t

-0.22 -

.0.24--

O LEADING EDGE DISPLACEMENT

A TRAILING EDGE DISPLACEMENT

-0.26- O NASTRAN

t

.0.28 --

; .0.3o I I I ! I

4 1600 3200 5000 7000 8000

SPEED-- RPM2

•J.t. 9000

{

"_.

," Fig.20 SR5PropFanTip PhotoResults-- BasedonAveraging Axial Displacement

84--4--7--19

52
SECOND MODE _,

, 4

NASTRAN TESTDATA THIRDMODE "

RELATIVETO ZERO SPEED BENCH TEST F()URTH MODE .

FIFTH MODE " f

800

€

7oo.- _1 ,-

(3 i., (3 !

600 _-- 0 t"

- I

"_ 500 r- _1 -I- 13

_tJJ IIz| .400 _

7-)

!

o

UJ

200 -- I

8 t

100 L.

o I I I I I I I

0 1000 2000 3000 4000 5000 6000 7000 8000

SPEED(RPM)

=_ Fig.21 SR5FrequencyvsSpeed ;

L

i l

!

t
I

0

II

w

...J

CJ

Z

«

w

(J)

«

I

a..

12 13

,

I

0

0

ex>

II

w

...J

CJ

z

«

w

(J)

«

I

a..

9 10 11

NORMALIZED STRAIN

2 8

7 6

V1

,.

....." 1,311...., ."'h,.r'\'r.~"'~;~-·" "":-." ·,.h.......,.....,.~._ ~' ••_.--' ..... ~-~...- --. ~....-.-- .... •• .. _""~=.-,i

Ii

"I

";

"

II>

..

I

..

I

....

I

Ul

o

Fig. 22 3R5 Blade Vibratory Strain Distribution Bench Test Results - Mode 1

,~

.. '
_ t.

\

\

"

.....

"--1 . ...-~

.' '" -" .. ~'. .

b-~

r··:.

~~~ ~'i

:J~ ....' , ;,' ~~

..,....

';11

,'/

" .' .._- - -...., .- . ,.., .. ..

0

'QI 0

~~ II

w

en

<{

:I:

'.. 7 3 a.. ;>

.. 4 9 10 11 12 13 I :1'11

;;(1) .-

NORMALIZED STRAIN . ,

0

0

co

II

w

en

<{

:I:

a..

\J1

\J1

CD

..

I

..

I

...,

I

..

"'

Fig. 23 SR5 Blade Vibratory Strain Distribution Bench Test Results - Mode 2
_._.. _•..•...:.'-_';:..<·;....:"_·'_.7_·._~_. -.. ~_•..::, ...":"~·-:""l,~._~_'''-''~~' =_-..,;.,. ........;.·;;;,,;;;.;;;;*1·[;!l4!m

NORMALIZED STRAIN

7 6 4 3 2

15

476 Hz

8

12 13

I

o

o

/I

wC/)

«

I

0..'

o

co

<Xl

..

I

...

I

....

I

POl

Fig. 24 SR5 Blade Vibratory Strain Distribution Bench Test Results - Mode 3

/I

wC/)

«

I

a..
, .. -..

f .... - .:...... ~:.

Fig. 25 SR5 Blade Vibratory Strain Distribution Bench Test Results - Mode 4

V1

-~

I

,.

I

...

I

,.

....

7 6

SUCTION SURFACE

/'

,.

3

599 Hz

2 15 8

NORMALIZED STRAIN

9

10 11

00

"'II:D

~~~~

.0'" ella

~c;)

r-I'II

~u;

1

0

0

II

w

-' C)

z

«

w

::I:

12 . 13 Cl.

j

II

w

-' C)

z

«

w

::I:

Cl.
-- 280 Hz

lo

PRESSURESURFACE

,I NORMALIZEDSTRAIN

1

I

U1

OO

Q

O

• II

• 6 _ ------= 9 10 11 3C

3 2 a.

12 13

,

II ILl

L "

I

,,,,j i i

Fig. 26 SRS Blade Vibratory Strain Distribution Bench Test Results _ Mode 5 ;
.I-J _._ -. :;- .... .-_-, .-:

.... ~-',,-- .-? '":i:;

1ST MODE AT 4000. 5000. 6000. 7000 RPM

• i

15

.i

PRESSURESURFACE t

NORMALIZED STRAIN

8_i8 b < '

@<BI_ , , , FT1

I

, 7 6 4 3 ,_ I'--'q l

r

• },_",_q 8 9 10 11 12 13

,<

• ,4

),d

oo PHASE ,_ _ 0 PHASE ,_ = 0

I

I 0 4000 RPM O

<] O 5600g 000RPMPM ,_I_1 Fig.27 Blade2 StrainModeShapeVariationwith Speed--.First

I> toooRPM I_ BenchModevs FirstMode at Speed

I
2ND MODE AT 4000. 5000. 6000. 7000 RPM

15

k--,

PRESSURESURFACE

V NORMALIZEDSTRAIN

o 4 0

,°, ___,r--] ,o ,,_

i

0

-_Bb 0 mASE<,,o PHASE_=0

== _--_ O O 4000RPMO

L <_ 5000RPM4

.O O Fig. 28 Blade 2 Strain Mode Shape Variation with Speed m Second Q ¢,ooohEM D :

I _ 7000 RP_! _, L: Bench Mode vs Second Mode at Speed •
* : ! j

w--

............... - o.. ° t_ ,

i

3RDMODEATZERORPM i

t

_,, SUCTION SURFACE . PRESSURESURFACE "_ }_It \ NORMALIZED STRAIN J

p

8,-, _

_-_ _ 15 10 11 12 13

7 6 4 3 2 8 9

0

• 0

0

PHASE ,_ _0 PHASE _ =0 0

, 9

=. O 4000nPM O 0

_' ' 13 ¢.,ooor_PM Fig. 29 Blade 2 Strain Mode ShapeVariation with Speed ThirdBench

=_ Mode vs Third Mode at Speed
4TH MODE AT ZERO RPH ___+_

ri

SUCTION SURFACE PRESSURESUR

NORMALIZEDSTRAIN

I

Ob

P 4.. o •

• )

o Q

10 11 12 13

7 6" 4 3 2 15 8 9 i.

t

O

PHASE ,_=0 PHASE ,_=0

w

b

! O 4000 FIPM O

• <I _oo()RPM< • Fig.30 Blado2 StrainModeShapeVariationwith Speed-- Fourth Era-

' E]_6000 RPM; flPU ,{_°(Ip, BenchModevs Fifth Mode at Speed °<oh
-= L ..... " . .

5IH MODE AT ZERO RPM

° 1

0< 1 0

o b 0 <I ,

7 4 i 15 O<:la 0 :I_ I 9 10 11 I

6 3 2 _ 8 12 13

t 04al > <1

I J

• j J " PHASE,4 #0 PHASE_ =0 <r-, o n

_ O I> Fig. 31 Blade 2 Strain Mode Shape Variation wlth Speed -- Fifth o ,mooRPM O

, I_ <I _ RPu <

Benlh Mode vs FourthMode at Speed D _nPu =1
E

10

['::

V NORMALIZED STRAIN 0 PRESSURESUR,._FACE _ €t 0

° I

I!

_ 0 "' ..a

._ X <) X 0

- €._

7 _,6 4 3 V--1 O15 I

,,. t'1 I I 2 l,,,...._-.-J B 9 10 11 12 13 l

x _ ;

, |l

X 0 X ..j"' (3

Z

BENCH TEST 113 HZ IJJ

X I 0 NASTRAN0 RPM 10,4Hz

" I X NASTRAN 7000 RPM I(;5 HZ "i0 _' "

I

,,

'

4 0

I

"- Fig. 32 SR5 Blade Vibratory Strain Distribution Comparison -- Mode 1
./

i *

;

i

.!

NORMALIZED STRAIN

--I

o_,n., 0 X lOx

II

iii I

x _T

n

0 x

7 6 4 15 O X

• U _>3X 0 2 X 8 9 10 11 " 12 13 o....ll

I.U X

O

A Z

v BENCH TEST 280 Hz "<:

uJ 0 NASTRAN 0 RPM 272 Hz (.f)

X NASTRAN 7000 FIPM 288 HZ

,..,.,,.,.. "T"

X 0 X "

'0

t.

, Fig.33 SR5 BladeVibratoryStrain DistributionComparison-- Mode 2 &

k)

i
i

°

o

I lo 11x O12x O x ,,)"'

76432<

X

XXI O. i' l

0

BENCH TEST 476 Hz_:)

G:)

O NASTRAN0 RPM 513 Hz""

II

XNASTFIAN7000 RPM 594 Hz ILl o x _"1"

1..

!,I ' _ Fig. 34 SR5 Blade Vibratory Strain Distribution Comparison

_ Mode3
j _

•,4 X '

, II UJ

' 0 10 11 12 13 cn i '<

' °'° L_JL:J i 7 6 3"" 02 15 8 9 "

": !

I L

_4THBENCH MODE 599 Hz _ cz)

0 NASTRAN5TH MODE 0 RPM 703 Hz II

X NARTf!lAN5TI! MODE IL)OOlif'M 1:_2Hz , UJ

: U3

! <

"!"

n

I

, == X

I

T' Fig. 35 SR5 BladeVibratoryStrain DistributionComparison-- Mode4
• 15

/

PRESSURESURFACE

NORMALIZED STRAIN

o _ _

o, _ 0 0

xx10 11 X

6 3 2

5TH BENCH MODE 641 HZ

0 NASTRAN 4TH MODE 0 RPM 631 I'lz

X NASTRAN 4TH MODE 7000 RPM 612 HZ 0 CO

• II

ILl

0 "'- 0 x o _o.. 0

" ; T

I

L Fig. 36 SR5 Blado Vibratory Strain Distribution Comparison _ Mode 5
APPENDIX I

MIRROR/LASER DATA

Oy vs. Speed

• 0Z vs. Speed

#
BLADENASTRAN COORDINATE SYSTEM

_, A1.A2.A3(BLADETIP) I

_:!' ORIGINALPAGEIS BLADE TWIST

- [ . "OF POORqUALri3f

(LOWER .yPOSITANGLE IVENOS OFATTACK DOW.N E )

[ LEADINGEDGE At

. _ MID-CHORD A2

i TRAILINGEDGEA3 _

0.1

0.04

0.02

0

0 30002

,.. 50002 70002 • , 8C002

ROTATIONAL SPEED2 -- RPM 2

Fig. 1.1 8y vs Rotational Speed2

s

84--4--7--_4

AI-2
ORIGINAPAGE L IS

I

I OF POORQUALITY

i BLADENASTRANCOORDINATESYSTEM

B1. B2.B3

,,

., MID-SPANe_yPOSITIVENOSEDOWN

LEADINGEDGE BI , ,

MID-CHORD B2....

. TRAILINGEDGE B3

t

0.16

0.14

0.04

0.02

0

" 0 30002 50002 70(302 80002

.I

; ......... ROTATIONAL SFEED 2 N RPM 2 _'..'o' " "_: "_

! Fig. 1.20y vs Rotational Speed2

( .1. m

B4--4--7--25

I

I AI-3

r
:,.',

I BLADENASTRANCOORDINATESYSTEM

• INBOARDC1.C2. C3

#y POSITIVENOSEDOWN

", LEADINGEDGEC1

MID-CHORD C2....

i" TRAILINGEDGEC3

_._

" _ 0.16

0.14

0.12

0.10

<:

rr"

I

t

>- 0.08

0.06

0.04

0.02

i

!

0

0 30002 50002 70002 80002

b.

l ROTATIONAL SPEED 2 -- RPM 2

.... _J . ...... .,_ ..... . -..... .

r_

ii Fig. 1.3 Oyvs Rotational Speed2

ir ' :

• 84,-4--7--26

-'_ AI-._
ontGtN_pAG t- _IS

i i • OFpOORquALrrY BLADENASTRANCOORDINATESYSTEM

Dr, D2

,,,; (ROOT)#y F_3fflVENOSEDOWN

"- IP" ,

:" LEADINGEDGE D!

TRAILINGEDGED2

0.08

0.07

0.03

0.02

0.01

0

0 30002 50002 70002 80002

. . _ - ROTATIONALSPEED2 -- RPM2......

..F

• , Fig. 1.4 Oyvs Rotational Speed 2

_;,,:'-"_ :' 84--4--7--27
BLADENASTRANCOORDINATESYSTEM

At. A2. A3

#y POSITIVETIP FORWARD

_" LEADING EDGE AI

MID-CHORD A2

TRAILING EDGE A3

-0.01

-0.08

f.

t.

: -0.09

[ 0 30002 50002 70002 80002

_ ROTATIONALSPEED2 -- RPM2

" ." " -_ ;' :" ...... ...... : i'. " •

Fig.1.5 0z vs RotationalSpeed2

,, A1-6

E
LEADING EDGE 81 ---

MIDoCHORD 82 - - --

TRAILING EDGE OJ - -

8LADE NASTRAN COORDINATE SYSTEM

MIDSPAN 81, 82, 8J /l y POSITIVE TIP FORWARO

~"".__•• r-.... _"'... ....,cC"..,.,.~. ""'--a~~.....' _......_-'-._~~

1:1 • r

" I

I ! I

- I • -I F;

l,'

,

.. '

.

f~

; ..

B

en

z

<

o

I

0.01

-o.oa

-0.10

-0.12

-0.14

o 50002 70002

ROTATIONAL SPEE02 - RPM2

Fig. 1.6 (}-: vs Rotational Speed 2

AI-7

80002

84-4-7_29
__"_ p t '''_ .....

..... _.f ._.--' ............................... . .... ;

!i_! " "I

INBOARD C1, C2, C3

zPOSITIVE TIPFORWARD

MID.CHORD C2 ....

TRAILINGEDGEC3--------

t -0.24

" i 0 30002 50002 70002 80002

,! :" "- ........ • ' ROTATIONALSPEED 2 _ RPM2 :.... "

"I ,.

.. "%

t

}:l Fig.1.7 0z vs RotationalSpeed2

_=_ 8,4--4--7--30

_ AI-8
1

BLADE NASTRANCOORDINATESYSTEM I_ R:_ DUALITY

"zPOST,P ,. _O. vE WA.D

t.

; LEADINGEDGE DI

I

TRAILINGEDGED2

-0.03

-0.04

-0.05

..... 3000........ 2 sooo2 ....70002 _oo02

:._ ROTATiONALSPEED2 -- RPM2 '

I .

2

_..- Fig. 1.8 0z vs Rotational Speed

F"le

_" F.4--4--7--31

_-, .A.I_9
ANALYSIS OF PHOTOGRAPHS GF BLADE TIP VECTORS

o

"'" The blade tip may be defined by a vector, V, from its leading corner to

its trailinp, corn,.r in an x,y,z coordinate _ystem of the rotor. #is _bown in

Figure 2.1, this coordinate system rotates by an angle 6, relative to the

x',v',z" coordinate systo.m of the spin rig. The camera was placed with its

lens axis along y" and used to record ph'otographs of the blade tip. In the

photographs, the three-dlmensional blade tip vector is recorded as a two-

. dimensional image on the surface of the film. The orientation of the image is

the same as that of a shadow cast by the tip, through cr.nter of the camera

lens. onto the film plan,,. This is a proiection along the unit vector _" in

Figure 2.1, which is eblique €o the film plane except when the blade tip is at

the c,ntor of the imam.,,fzeld. With the lens axis of the cam,,ra in the plane

of rotation of the blade tip, the obliq,Jity of _ is completely defined by Y,

the angle between _' and _'" in the y'.z" plane.

The blade tip vector on the photographs may be related to the actual

blade tip by three transformations. First the tip rotates due to blade

deformation. Next, the entire rotor rotates to some position at which the

photograph is exposed. Third, during the exposure of the photograph, the

vector that results from the previous operations is projected onto the film

plane through the center of the lens. Each of these transformations may be

described as a matrix that operates on the original blade tip vector, and tbu

total result is the nroduct of the three matrices in the proper seq,once.

Let the original blade tip v'ector be

V = x + y + kVz , (I)

where the subscrlp:s x, y, and z denote the respective components of V.

Deformation of the blade will rotate a surface element at the tip through an

angle O. If Ois small, the trailing corner will be displaced from its

original position relative to the leadlnz corner bv a vector ^ wh,_ro

A= 8xV . (2)

• ",." " ._7.', ............. ... -', ........ :.""'i '; ' "......... . ....

.e

..i

. t

!

-_ AII-I
s• .11

6

,_ & will lie at right angles to V and the new tip vector, VI, will be

Vd" V+ &- V + 8 xV (3)

The vector product in Eq. (3) can be written as a matrix operation, and this

allows reformulation of the entire equation as follows.

vd- v [i-ol, (4)

where

[t-eJ. -ez 1 ex • (s)

ey - 8x I

: Note that if the surface element rotates about an axis parallel to the blade

: tip, the orientation of the tip vector is unchanged.

The rotation of the rotor retatlve to the laboratory can be described by

a coordinate transformation matrix iT].

I ° el

[TJ = 0 cos_ sin_ . (6)

0 -sin_ cos_J

The deformed and rotated tip vector, Vdr , is

Vdr- v [z-el[TJ . (7)

The projection Vdr through the center of the lens onto the film plane is

described by the oblique projection matrix, [ejsJ.

[Pjs J == [I J- ]'_ ;i_'.; , (8>

,

:_ where _ indicates a matric product (dyadic, Ref. 9, p. 170) of the two vectors

"" and • indicates a scalar product. This matrix may be evaluated to be

o l

i

.. _ s.

.... _.-_

-. "i AII-2
'i

_t

-t [PjsJ "f0 ooj 0 tany . 49)

;"'; 0 O 1

The parameter tanY accounts for the spherical perspective of the camera. The

• angle Y is related to the angle _ as shown in Figure 2.2. If L and R are the

distance respectively from camera lens and the blade tip to the center o£ the

rotor, then

siny s in(_-_o)/[I+(L/R)2 (2L/R)cos(___o)}I/2. " - (to)

€o is the angle at which the blade tip is located in the rotor coordinate

system,

The final equation for the image of the blade tip vector may be written

as

vc = v[x-ej[tJ[Pjsj • 411)

The matrix products may be evaluated as follows:-

[tl[P"js[J 0 0o.i._cos,ta ],._ 4_2)

0 cos_-sin_tany

and

l o eZ(ai.*+¢os*tan'-OOz(_os,-sin,tan-Ol

[c-0J[t][Pj=s]-oz 0 (sin_+cos_tany) + Ox4cOs_-sin_tany) . 413)

.... 0y 0 -Ox(Slnd_+cos_tany)+ (cos_b-sln_tany)

Equation (13) may be simplified by the following substitutions.

C = sin_b+ cosCtany, and

,.A

._ D = cos_- sin_tany

io

" ' AII-3

..
f

Substituting these into Eq. (13) and the result into Eq. (II) gives t

i

Vc: {Vx'Veyz.vzeY.} '{ccVxez*Vy'V) ze- Dx Vxey-VyeX-V. z)J 14)

! With the additional substitutions,

A = Vz/Vx, and

B = Vy/V x ,

it is possible to describe the angle of the image of the blade tip in the photograph as,

cots = [A(D-C_X) . B(C+Dex) + COz_Vey}/(l.Bez+Aey} . (15)

"- , Nhen the blade def0rmarion is zero, this reduces to

cot% = AD + BC . (16)

Photographs were taken of the blade tip at zero speed for various values

of rotor angle, €. For each of these, the corresponding value of a was

neasured on the photograph, and the corresponding parameters C and D could be

computed. These sets of values were applied to Eq. (16) and used to generate €

values of A and B that be'stflt the data. The components of V were measured "

on blade lO in the spin rig and the values of A and B were computed to be

-.9118 and -.1471 respectively. The corresponding numbers from th_ data fit

_ere -.9150 and -.1590 respectively, which show good agreement. Without the

perspective correction, the values obtained were approximately -.88 and -.33,

which confirms that perspective may not be neglected.

Equation (15) in this analysis shows that the angle a may not be used to

measure the component of blade rotation By unless both parameters B and C

are negligible. This is not generally the case, a_d it is practical only to

use Eq. (15) together wlth other knowledge of 0y and ez to solve for eX. This

results in a complete determination of the deforn_atlonthat may be compared with numerical analysis.

AII-4

m .......
_-v,'. ̧i

- ; ..

L_

_. :",i.;

From Eqs. (15) and (16), and since

'.,i _ cota =-csc2a, cOtao-COta×(a-ao)/Sin2 a

,,, dot

8 then

{Acota+DJOy = (RD-AC)Ox+(C+Bcota)Gz+(a=ao)/ain2a (17)

• Applying Eq. (17) to 7,000 RPHconditions as follows:

_X " -0.108 tad (NASTRANCalculation)

0¥ = 0.0661 rad ( Measured from Laser/Hirror data

OZ = -0.046 tad _ extrapolated to tip

= -0.047 rad (Avg blades 1,2,8,5)

yields a value for a-ao of 0.0593 rad as shown in Figure 17.

..t

o

_'°iI. .....

i¢

T

--, AII-5

.!
i

f

€

J

I

f

!-

Fig. 2.1 Axis Systemfor Analysis of Tip Photographs

., • . . .

84...-4--7-51

AII-6
:i;.. '

i,i

•_! 4 ,

BLADETIP

a

CAMERA - PIUB

Fig. 2.2 Spherical Perspective Geometry

,...o

• .°,

". i

. '-!

- I =.L-4-7-_

"- AII-7
,.','I

,i

APPENDIX Ill

DYNAMIC DATA REDUCTION

As was explained in Section VIII, rotor system dynamic characteristics

were recorded during free decay of vibration from an imposed excitation. The

identification of modal elgenvalues and eigenfunctlons from a digitized time

series of strain gage readings was accomplished by an adaptation of the rime

; domain procedure of reference 8. Ti=e Domain Analysis is based on the assump-

• tion of a linear system, the free response of which is approximated by the

number of modes equal to the number of time steps used in the series. For

example, the blade modes of the SR-$ rotor were extracted by selection of da:a

from 12 strain gage outputs. Only $0 of the 1024 time steps were used in a

given analysis, consequently, system dynamic properties could be evaluated a_

several points in the decay.

In the present application, three matrices each 25 x 50 were formed st

times, t, t+A, and t+2At. For the SR-5 rotor, the 50 time increments covere_

• _ approximately three cycles of the lowest frequency of interest and approxi-

! mately twenty cycles of the highest frequency. The delay time, _t is fifteem

: time increments. A second delay time 2_t is used to enlarge each 12 x 50

array into the 25 x 50 array required, as sho_n in Figure 3-I.

The time domain forms two 50 x 50 matrices

!

i and solves the resulting eigenvalue problem

i

I

t xi *i

I

oW

1 AIII-1
f

[ for the complex elgenvalues Xi and elgenvectors _i. This problem is

closely related to the dynamic elgenvalue problem of the linear system which

was assumed as a model, the vectors being identical and the elgenvalues being

simply related.

In addition to the modal frequencies, damping factors and normalized

complex mode shapes, a modal confidence factor is obtained. This is a measure

• of the predictability of the actual data from synthesis of the modal structure

data fit described above. The modal confidence factor is the ratio of the

predicted modal value at a time 2At later to the actual modal data. This

complex ratio is expressed as a percent in _nplitude and degrees in phase.

.!

I

-!

AIII-2
, #'# ' , m • .. ,,.

,_ 1 1 l I

I x r : xt+1 xt+2 . . , xt+49

ii. .......

' 12 12 12 12

-_ t Xt+l xt+2 " * " xt+49

m

" 1 1 1 1

X _ xt+ 2 xt+ 3 xt+4 . . , xt+51

12 12 12 12

xt+2 xt+ 3 xt+4 • . ; xt+51

1 1 1 1

xt+4 xt+5 xt+6 " " " xt+53

m

1 1 I 1 --

xt+15 xt+16 xt+17 • • . xt+64

• • e • • • •

:' 12 12 12 12

xt+15 xt+16 xt+17 • . . xt+64

1 i I 1

Y _ xt+17 xt+18 xt+19 • . . xt+66

• • • eee •

12 12 12 12

xt+17 xt+18 Xt+l 9 • . . xt+66

i 1 1 1

xt+19 xt+20 xt+21 • . . xt+68

1 1 1 1 -

xt+30 xt+31 xt+32 • . . xt+79

12 12 12 12

'xt+3- xt+31 xr+32 • . . xt+79

i i i I

Z E xt+32 xt+33 xt+34 • • * xt+81

• • • ooo •

12 12 12 12

xt+32 xt+33 xt+34 • . . xt+81

"

e_

"

"

-- xt+31 4 _ +35 xt1+36 •

eo xt+83 1

_- ig. 3.1 DataArraysfor BladeMc<les

,. me.

k2 " _--4--7--_

W_.
APPENDIXIV

NASTRANRESULTS

CharlesLawrence

NASA

.°

.i

2

t

AIV-I

[.
NASALewisResearchCenterpersonnelprovidedanalyticalresultsfor SRS

usingthe finiteelementprogram,NASTRAN.Theseresultswereobtainedto

" determinethe extentof correlatioben tweenfiniteelementanalysisand

i

experimentatel sts. The levelof correlatiobetwee n nthetwoapproachesis

i

discussedthroughouthisreport. A summaryof theNASTRANsteadystate

dlsplacements,frequenciesan, dmodeshapearepresentedin thisappendix.

i Thefiniteelementmodelusedfor theNASTRANanalysisis shownin Figure

6. Thismodelconsistsof 882 triangulaprlateelements(CTRIA3)and517 node

il points. The plateelementformulationIsncludebothmembraneand bending

action.The baseof thebladerootismodeledas fullyconstrained.This

constraintdoesnot allowfor anycoupllngthatmayexistbetweenblades.

j NASTRANSolutionsequence64 was usedto computetheblade'ssteadystate

displacementsproducedby thecentrifugalol ading.Sincetheturbopropblade

is relatlvelyflexible,it respondsto loadingwithrelativelylarge

deflections.Thecomputationof thesedeflectionres quiresa geometrically

nonlinearanalysiswhichSolution64 is capableof performing.

Solution64 utilizesa modifiedNewton-RaDhsonalgorithmto solvethe

geometricallynonlinearproblem.The Newton-Raphsaolngorithm,whichis an

iterativeprocedure,requirednineiterationtos adequatelyconverge.After

convergence,the steadystatedisplacementares printedout andthecomputed

structuralmassand stiffnessmatricesarestoredfor the subsequenfrequen t cy

analysis.The NASTRANprogramis alteredso thatthecentrifugalsoftening

t

terms,whichare normallyneglected,areincorporateinto d thefinalstiffness

matrix.

AIV-2
. o

I

o

• p

i

i

2

•_t q

:i Figures4.1 thru4.6 showthecomputedbladerotationsat thevarious

. mirrorlocations.Theserotationscanbe comparedto theexperlmentally

obtainedrotationsin Figures1.1thru1.7. NASTRANcomputedblade

. displacementsin theX andZ directionare shownin Figures4.7 and 4.8

respectlvely.The X directiondisplacementcsanbe comparedto the tipphoto

resultsin Figure20.

NASTRANSolution63 was usedto extracttheresonantfrequencieand s mode

shapesfromthe massand stiffnessmatricesgeneratedby the geometrically

_ nonllnearanalysisperformedin Solutlon64. Solution63 was usedforthe

i

frequencyanalyslsbecauseit is directlycompatiblefortransferringmatrices

fromSolution64. Thecomputedfrequencieand s mo:Jeshapesare shownas a

functionof rotationalspeedin Figure4.9.

AIV-3
........ ................ f

i NASTRAN

At. A2. A3 iBLADE TIPI

BLADE TWIST

f #y POSITIVENOSE DOWN

w'_ (LOWERANGLE OF ATTACK_

:.l

LEADING EDGE At ,

MID.CHORD A2

TRAILINGEDGE A3 _m

0.16

0.14

At

A2

A3

' 0.12

.i

' 0.10

0.04

1

0.02

!

' 0

•i 0 30002 50002 70002 80002

:".'-" ROTATIONALSPEED2 -- RPM2

.f

..' .._• " .

Fig. 4.1 Oyvs Rotational Speed2

84--6--42--1

" '

-,

• AIV-4

• o

•-. . _ .. •.-

• . . ..

" - . :" ,, L" -'. ..-_.'" : . '

.... _ "" , "__ ,_ ","" - " - "-..... :i' ...... 

,.,.;:- - , .....
ORIGINALPAGEL3

NASTRAhl OF POORQUALITY

B1, 02, B3

MID-SPAI'I ey POSITIVENOSE DOWN

LEADIFIGEDGE BI

MID-CHORD B2

TRAILI/'JGEDGE B3 _ ,,,-,

0.16

0.14 i[31

0.12

2

0.04

0.02

0

0 30002 50bO2 70002 80002

I ROTATIONALSPEED2 -- RPM2 "

.:

; Fig. 4.2 0y vs Rotational Speed2

1

I

i 84-6-42-2

AIY-5
, NASTRAN

'; INBOARD Ct. C2. C3

., ey POSITION NOSE DOWN

=B

" I

LEADING EDGE Cl

i MID-CHORD C2

; TRA_LIhIGEDGE C3

0.16

0.14

: 0.02

f. 0

!: 0 30002 50002 70002 80002

"-" ;. ROTATIONSPEED 2 -- RPM2

.B t

.°;. if

: l Fig. 4.3 0y vs Rotational Speed 2

_1 -- 84--6--42--3

" AIV-6
!

d e • _°_ I

I

; NASTRAN

'" \ At. A2. A3

." _tz POSITIVETIP FORWARD

.**..

f..

LEADING EDGE AI •

MID-CHORD A2

- TRAILING EDGEA3 ----==-.-.

-0.01

A3

-0.07

"_A2

-0.08

"0.09

0 30002 50002 70002 80002

"" " ROTATIONALSPEED2 b RPM2

!-_: Fig. 4.4 ez vs RotationalSpeed2

let

i,. :" ; 84--6--42--4 i(--_..i

_- AIV-7

- ° . t
t

NASTRAN

MIDSPAN B1. B2. B3

0Z POSITIVETIP FORWARD

f_ i LE.ADtNGEDGE BI-

| MID-CHORD B2

- i TRAILINGEDGEB3.----.-_

I,

i 0.02

i

i

o ,

i

_ 0

, -0.02

', -0.04

|

O'3

Z

_<

Q

'<tr. -0.06

I

-0.08

I

; -0.10 t

1

!

.1

t -0.12 a2

!!

i

i -0.14

! 0 30002 50002

i 70002 80002

,i ROTATIONALSPEED2 _ RPM2

'I

t

1

j Fig.4.5 0Z vs RotationalSpeed2 ,

k ,' 84-6---42--5 i

AZV-8 l
O_IGINALPAGEIS

O$ POORQUALIFY _ASTRAN INBOARD C1,C2. C3

#Z POSITIVETIP FORWARD

LEADINGEDGE C1

MID.CHORD C2

TRAILINGEDGE C3

0.08

€

0.04

0

-0.24

0 30002 50002 70002 80002

ROTATIONALSPEED2 -- RPM2

Fig. 4.6 ez vs RotationalSpeed2

84--6-42-6

AIV-9
3000 RPM 5000 RPM 7000 RPM 8000 RPM !J

0.021 in. :f

1.171m ;_.

1 in

0 143 in.

O 09 m. 3 114 in.

0.014in. 0.06iny/ I _/-0 06 in. 0.086in. -0086 m.

_}.007in. _ I/ I/+°_"" oo_,o oostin.

0.007 in. o 029 in.

o 0.029 in

,in. 0 m.

t

Y Y Y y z

Lx L, Lx - Lx "

RO,4.7 NastranDisplacementConioursX Direction

!
3000 RPM 5000 RPM 7000 RPM 8000 RPM ,.;./,!

=ll;_•

0.12 in. 0 m. :_

006in "1'

0 04 ,n ; m. _,.;

...f.

) =n 3 08 =n C)12 in.

Ot6m _. z

0.04 in. 0 in. -0 04 =n -O 12 m .(318 m /"

0 181n

0 08 m. 0 12 m -0 02 m.

0.02 in. 008 m 0 t2 m

0 04 tn

I'_ 0 0.1 in. 0 06 tn

I"-= t

y Y Y y

Lx Lx Lx ,...

Fig. 4.8 Naslmn DisplacementContoursZ Dimclion

I

I

I

W
$

! %

800

700 _ J

J

600_

500

t N

o

z 400

O

300

200

100_

0

0 2000 4000 6000 8000

BLADEROTATIONALSPEED (rpm)

Fig.4.9 NestranFrequenciesandPositionof NodeLines

.... I

.=._

°

• ale,:

__.._. 114--6--42--9

•;. AIV-12
ID
IIliiiiiiiiiliiiiiiiiii III

3 1176 01344 0764

°

_J

I