NASA Technical Memorandum 4760

ARL Technical Report 1389

Rotating Shake Test and Modal Analysis of a

Model Helicopter Rotor Blade

W. Keats Wilkie, Paul H. Mirick, and Chester W. Langston

Vehicle Technology Center

U.S. Army Research Laboratory

Langley Research Center • Hampton, Virginia

National Aeronautics and Space Administration

Langley Research Center • Hampton, Virginia 23681-0001

June 1997
Available electronically at the following URL address: http://techreports.larc.nasa.gov/llrs/ltrs.html

Printed copies available from the following:

NASA Center for AeroSpace Information

800 Elkridge Landing Road

Linthicum Heights, MD 21090-2934

(301) 621-0390

National Technical Information Service (NTIS)

5285 Port Royal Road

Springfield, VA 22161-2171

(703) 487-4650
Summary

Rotating blade frequencies for a model generic helicopter rotor blade mounted on an articulated hub were

experimentally determined. Tests were conducted using

the Aeroelastic Rotor Experimental System (ARES) testbed in the Helicopter Hover Facility (HHF) at langley

Research Center. The measured data were compared

with pretest analytical predictions of the rotating blade

frequencies made using the MSC/NASTRAN finiteelement computer code. The MSC/NASTRAN solution

sequences used to analyze the model were modified to

account for differential stiffening effects caused by

the centrifugal force acting on the blade and rotating

system dynamic effects. The correlation of the MSC/

NASTRAN-derived frequencies with the experimental

data is, in general, very good although discrepancies in

the blade torsional frequency trends and magnitudes

were observed. The procedures necessary to perform a

rotating system modal analysis of a helicopter rotor blade

with MSC/NASTRAN are outlined, and complete sample data deck listings are provided.

Introduction

Calculation of the rotating system modal properties

of rotor blade and hub assemblies, particularly in the case

I

of bearingless hub designs, often requires the use of

modern finite-element computer codes. One widely used

finite-element code is the commercially available MSC/

NASTRAN program (refs. 1-4). Although a rotating system modal analysis can be performed using the standard

release versions of MSC/NASTRAN, some potentially

significant dynamic effects caused by rotation will not be

accounted for properly. By modifying the standard MSC/

NASTRAN solution sequence to include the additional

rotational effects, a more accurate modal analysis of a

rotating structure may be performed. This report documents an experimental evaluation of the ability of this

modified MSC/NASTRAN procedure to accurately predict the rotating blade frequencies of a model articulated

helicopter rotor blade.

Experimental Apparatus and Procedures

Test Facility

Tests were conducted in the Langley Helicopter

Hover Facility (HHF) shown in figure 1. The HHF, a

high-bay facility enclosed by a 30-ft by 30-ft by 20-ft

coarse-mesh screen, is used for hover testing and rotorcraft model buildup and checkout prior to testing in the

Langley Transonic Dynamics Tunnel (TDT). Models are

mounted on the test stand such that the rotor plane of

Figure 1. Helicopter Hover Facility (HHF).

L-78-5962
Table 1. Properties of Model Rotor Blade

(a) Structural properties

Inboard

section radius,

in.

3.00

6.87

8.87

10.625

12.50

13.00

15.375

17.85

23.75

28.25

51.00

52.75

53.00

54.00

54.25

Section spar

area, in 2

5.50

0.371

0.371

0.371

0.377

0.386

0.339

0.278

0.249

0.224

0.247

0.279

0.305

0.099

0.05

Chordwise area

moment of

inertia, in 4

0.5000

0.1500

0.0250

0.0250

0.0355

0.0252

0.0252

0.03040

0.02636

0.02447

0.02447

0.02448

0.0500

0.0400

0.0050

Flapwise area

moment of

inertia, in 4

0.5000

0.0500

0.0040

0.0040

0.00394

0.00249

0.00249

0.00231

0.00181

0.00151

0.00151

0.00160

0.00500

0.00400

0.00050

Torsional area

moment of

inertia, in 4

0.2632

0.1316

0.0105

0.0105

0.0394

0.00976

0.00976

0.00674

0.00565

0.00485

0.(X)485

0.00502

0.01435

0.01148

0.01435

Section mass,

lb/in.

0.4251

0.1938

0.04086

0.15113

0.14048

0.03134

0.04376

0.04123

0.0400

0.03903

0.03903

0.04125

0.07867

0.0607

0.01101

Section mass

moment

of inertia,

in-lb2/in.

0.2200

0.04826

0.02505

0.05671

0.05559

0.02779

0.02961

0.02888

0.02810

0.02756

0.02756

0.02826

0.03984

0.03563

0.004401

Center of mass

offset forward

of elastic axis,

in.

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

-0.106

-0.170

-0.940

(b) Assumed material properties

Modulus of elasticity, lb/in 2 Poisson's ratio

1.0 x 107 0.3

rotation is effectively out of ground effect (15 ft, or

approximately 1.6 times the rotor diameter). All hover

testing in the HHF is conducted at sea level atmospheric

conditions.

Model Description

A four-bladed articulated rotor hub, with coincident

lead-lag and flapping hinges, was used in this experiment. The structural and inertial properties of the model

blades are listed in table 1. The blades were rectangular

in planform and possessed no built-in twist. A standard

NACA 0012 airfoil contour was used over the aerodynamic portions of the blade. One blade was instrumented

with flapwise, chordwise, and torsional-direction strain

gauges mounted at three radial locations. The blade planform geometry, with strain-gauge locations indicated, is

illustrated in figure 2.

The testbed for this experiment was the NASA/U.S.

Army Aeroelastic Rotor Experimental System (ARES)

model shown in figure 3. The ARES model has a streamlined fuselage shell that encloses the rotor controls and

drive system. The fuselage shell, which is not usually

installed when testing the ARES model in the HI-IF, was

omitted during this test. The model rotor is powered by a

variable-frequency, synchronous electric motor (rated at

I- Flapping and lead-lag

hinge location Pitch axis (e/4)7

[ Strain gauges /

3 0 I_ (0.179, 0.539, 0.749) /

Center-- +_-- ]. _ ......L.... [ /--x

of ;

r°tati°n-_l LI [4.24

6.a7-- I I

._-12.5---I 55 0

Figure 2. Rotor blade geometry. R is blade radius, and c is chord;

all dimensions in inches.

47-hp output at 12000 rpm) that is connected to the rotor

shaft through a belt-driven, two-stage, speed-reduction

system. Collective pitch and cyclic pitch inputs are provided through a conventional swashplate arrangement.

The swashplate is positioned by three electrically

controlled hydraulic actuators, which are controlled

remotely from the HHF control room. Signals from the

blade strain gauge, as well as the signal from a straingauge-instrumented pitch link signal, are transferred

from the rotating system to the fixed system through a

30-channel slip-ring assembly.
Figure 3. ARES model mounted in HHF.

L-86-11,726

Test Procedure

The experimental portion of this test was designed to

provide accurate measurements of elastic blade mode

frequencies over a range of rotor operating speeds. The

experimental procedures described below are not necessarily the ideal techniques for experimentally measuring

rotating blade frequencies, but are the best use of the

existing ARES hardware and instrumentation for this

purpose. For this experiment, only elastic blade modes

with frequencies up to and including the first torsion

mode were measured. Because of the limited blade

instrumentation, no attempt was made to measure blade

mode shapes during this test.

Rotating-frequency measurements for each mode

were made at rotor speeds that ranged from 150 rpm to

660 rpm at approximately 100-rpm intervals. The

nonoscillatory collective pitch of the blades was fixed at

0 °. At each rpm increment, the blades were excited by

sinusoidally oscillating the collective pitch of the rotor

with the ARES hydraulic control system. This collective

pitch oscillation frequency was varied over a 10- to

20-Hz frequency band in the vicinity of each modal frequency. The amplitude of vibratory loads caused by the

movement of the swashplate together with the small

amount of aerodynamic excitation present from the collective pitch oscillation was sufficient to excite all of the

blade modes of interest.

Blade mode frequencies were determined by processing blade and pitch-link strain-gauge signals with an

electronic signal analyzer. Output signals from the blademounted strain gauges were used as a measure of the

blade modal deflection, while the pitch-link-mounted

strain-gauge signal was used as a measure of the force

input to the blade structure. From these two measurements, a frequency-response function could be generated

using the signal analyzer. The frequency of the excited

blade mode was then identified by looking for an amplitude peak in the frequency-response function.

Nonrotating modal frequencies were determined

with a different procedure. For these measurements, the

hub assembly, with a single attached blade, was removed

from the ARES model and suspended so that the blade

hung vertically. This method permitted measurements to

be made without the blade resting on the hub flapping

stops. A conventional impact-response test using a blademounted accelerometer, a signal analyzer, and an impact

hammer was then performed. Nonrotating blade mode

frequencies in this case were identified by looking for the

amplitude peaks in the spectral-response function generated with the accelerometer signal.

NASTRAN Analysis

Blade Analytical Model

Analysis of the articulated rotor blade was performed using several versions of the MSC/NASTRAN

finite-element-analysis computer code. The original,
pretestrunswereperformedusingMSC/NASTRAN

version 66b. Subsequent runs using version 67 and, more

recently, version 68 were made to verify that procedures

used with previous versions were still applicable and that

the results had not changed.

The blade analytical model was constructed using

standard finite-element-modeling techniques. A list of

the complete input data deck is provided in appendix A.

All material and structural property values for the blade

model were taken from values shown in table 1. The

blade structure was modeled entirely with CBEAM

one-dimensional beam elements, with sectional masses

and mass moments of inertia for all elements modeled as

nonstructural mass.

The blade-root boundary conditions were approximated by allowing rotations only about the Y- and Z-axes

of the global coordinate system, which represented

motion about the flapping and lead-lag hinges. The

blade-root lead-lag damper was modeled using a

CELAS2 scalar spring dement with an appropriate

damping value and a small linear spring rate. Rotation

about the X-axis (blade pitching degree of freedom) was

constrained to be zero, representing in essence an infinitely stiff control system.

Rotating System Analysis Procedure

MSC/NASTRAN and COSMIC/NASTRAN have

both been used to analyze the rotating modal behavior of

compressor and turboprop blades (refs. 5 and 6). In these

studies, plate, shell, and solid elements were used to

model the blades. The computational procedure used in

these studies required that two MSC/NASTRAN runs be

made for each condition. First, a large-displacement

analysis was made using MSC/NASTRAN solution 64.

This solution sequence performs a large-displacement

analysis on the rotating blade, computes steady-state

displacements and stresses, and then stores the blade

final stiffness and mass matrices of the blade model in a

database. The frequencies and mode shapes were then

computed with solution 63, using the saved matrices

from the solution 64 run.

The current study also used a two-step process to

obtain the blade frequencies and mode shapes although,

as mentioned previously, beam elements are used here

to model the rotor blade. At each desired rotor speed condition, the blade model was first analyzed using the

nonlinear statics (database) MSC/NASTRAN solution

sequence 66, which is the updated version of solution 64.

This run calculated the deflections of the blade structure

caused by a radial force field defined with the RFORCE

card in the bulk data deck. Gravity forces and aerodynamic forces were neglected throughout this analysis,

4

and only forces acting on the blade as a result of rotation

were considered. The MSC/NASTRAN executive control cards, case control cards, and bulk data used for a

sample solution 66 run are included in the listing in

appendix A.

Once the smile analysis of the blade had been completed, a modified normal modes analysis (solution 63)

was performed as a "restart" job using the MSC/

NASTRAN database files generated and saved from the

solution 66 run. Two modifications were made in the

solution 63 DMAP code to obtain the correct rotatingblade mode shapes and frequencies of the structure.

The first modification was the inclusion of a standard

MSC/NASTRAN rigid format DMAP alter (RF63D89)

into the solution 63 source code. This DMAP alter

allowed the stiffness matrix generated and saved from

the solution 66 run, which included the differential stiffening effects of the radial forces acting on the rotor

blade, to be used instead of the stiffness matrix normally

generated in the solution 63 run. A second DMAP modification (NLGYRO.ALT) was made to include additional centrifugal softening terms in the stiffness matrix.

NLGYRO.ALT also adds Coriolis terms to the damping

matrix; however, for the normal modes analysis

described here, damping and Coriolis terms can be

ignored. This modified solution 63 DMAP source code,

with the RF63D89 and NLGYRO.ALT DMAP alters

included, was then recompiled and executed as a restart

job using the previously generated solution 66 database

files.

The nonrotating (0-rpm) case required no initial nonlinear statics run and was performed using the unmodified solution 63 normal-modes solution sequence.

The executive control cards and case control cards

necessary to execute the solution 63 runs are shown

in appendix B. Changes required between MSC/

NASTRAN version 68 and earlier versions (66 and 67)

are noted. The RF63D89 alter code, provided in the general distribution of MSC/NASTRAN, has not been

shown here. The NLGYRO.ALT alter code, which was

written originally for use with version 66b and is not usually provided in the general distribution, was obtained

independently from MSC. Several modifications to this

DMAP alter are necessary for it to be used with MSC/

NASTRAN version 68. These modifications are noted in

appendix C.

Presentation of Results

A comparison of the experimental and analytical frequency results is shown graphically in figure 4. This plot

shows blade mode frequencies (Hz) versus rotor speed

(rpm) for the first five elastic blade modes. The solid
Experiment

o First flap

r_ Second flap

First chord

o Third flap

• First torsion

125

100

N

-1-

>_ 75

o

50

25

-- Analysis

LL

J

Jo

Jo

J o

o

o o

[] jl

J

Z

I I I I I

0 150 300 450 600 750

Rotor speed, rpm

Figure 4. Comparison of experimental and analytical frequencies

vs rotor speed. Rigid body flap and lead-lag modes not shown.

lines represent the analytical predictions of the blade

mode frequencies made by MSC/NASTRAN. The

symbols denote experimental frequency values measured

in the HHF. A comparison of these experimental and

analytical frequency values is also provided in table 2.

Analytical calculations of the flapping and lead-lag rigidbody mode frequencies have been omitted. Repeatability

in the frequency measurements was within +l Hz for the

three flapping modes measured, and _+2 Hz for the chordwise and torsion modes. Variations in the rotor rpm

settings were very small, typically less than :t2 rpm.

Discussion of Results

The correlation of the MSC/NASTRAN-computed,

rotating-blade frequencies with the experimentally measured frequencies was, overall, very good, with the best

results being obtained for the lower flapping and chordwise modal frequencies. With the exception of blade

torsion, trends in mode frequency with rotor speed were

adequately predicted by the analysis. The largest discrepancies between the analytical and experimental results

occurred with the third elastic flap mode results and the

first torsion mode results.

The discrepancies with the third flapping mode were

thought to be due to inaccurate flapping stiffness data

used in defining the analytical model. MSC/NASTRAN,

when given accurate structural modeling information,

generally does an excellent job of predicting the nonrotating modes and frequencies of a structure. As the

nonrotating-frequency calculation for this mode was still

significantly in error with the experimental value, the

difference is thought to be due to the structural modeling

of the blade and not a fundamental error with the MSC/

NASTRAN procedures used in this study.

The discrepancies in the torsional frequency magnitude are thought to be due primarily to the "infinitely

stiff" control system approximation used for the blade

root boundary conditions. A finite stiffness associated

with the pitching degree of freedom at the root would

move the frequency magnitudes upward toward the

experimentally measured values. The slight upward trend

of the measured frequency with rotor speed was also not

predicted in the analytical results. This trend is thought to

be caused by the absence of a propeller-moment-type

term in the NLGYRO.ALT alter code.

Table 2. Comparison of Experimental and Analytical Blade Frequencies

Frequency, Hz at rotor speed of---

0 rpm 150 rpm 250 rpm 350 rpm 450 rpm 550 rpm 660 rpm

Exper- Exper- Exper- Exper- Exper- Exper- ExperMode iment Analysis iment Analysis iment Analysis iment Analysis iment Analysis iment Analysis iment Analysis

1st flap 10.7 11.53 12.2 13.10 14.7 15.51 17.6 18.52 21.2 21.91 24.9 25.51 28.8 29.62

2nd flap 32.6 36.38 33.1 37.64 35.8 39.78 39.0 42.77 42.7 46.44 46.7 50.63 51.75 55.69

1st chord 41.0 42.44 41.1 42.82 42.8 43.49 44.4 44.48 43.0 45.75 45.2 47.30 49.1 49.29

3rd flap 67.8 76.80 70.0 77.97 72.5 80.01 75.3 82.95 80.4 86.70 85.3 91.11 91.5 96.52

1st torsion 110.3 102.05 1i 1.0 102.06 110.0 102.09 112.0 102.12 113.0 102.18 114.5 102.28 115.0 102.53

5
Concluding Remarks

The rotating frequencies of a model articulated helicopter rotor blade were measured and compared to

analytical frequency calculations performed using the

MSC/NASTRAN finite-element structural analysis computer code. These results show that MSC/NASTRAN

can, with slight modifications, adequately predict flapping and chordwise rotating modal characteristics of an

articulated helicopter rotor blade structure. Accurate

prediction of torsional frequencies and trends will most

likely require some additional modifications to the MSC/

NASTRAN DMAP source code.

NASA Langley Research Center

Hampton, VA 23681-0001

January 22, 1997
Appendix A

MSC/NASTRAN Solution 66 Input Data Deck

The material in this appendix constitutes the complete input data deck used to construct the blade analytical model.

SSS$$$S$$$SSSSSSS$$$SS$SSSSSS$$SSSSSSSSSSSSSSSSSS$S$$SS$$$SS$SS$$SSSSSSSSSSS

$$ EXECUTIVE CONTROL CARDS $$

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

$

ID ART-L, WKW

SOL 66 $ NONLINEAR STATICS (MSC/NASTRAN VERSIONS 66, 67 OR 68)

TIME 20

CEND

$

$$$$$$$$$$$$SSSS$SSS$S$SS$$S$SSS$SS$SS$SSSSS$$SSSSSSS$SSS$SSS$SSS$SSSSSSSSS$

$$ CASE CONTROL CARDS $$

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$S$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$S$$$

$

TITLE-FRB (LIGHT BALLAST) ON ARTICULATED HUB

LABEL-(CF LOAD II HZ ROTATION)

SUBTITLE- NONLINEAR STATICS SOL 66

$

ECHO-BOTH

DISP-ALL

OLOAD=ALL

$

SEALL-ALL

$

LOAD-I

S

NLPARM-100

S

BEGIN BULK

$

$$$$$$$$$$$$$$S$$SSSSS$$S$$S$SS$$S$$SSS$SSS$$SSS$SS$SSSS$SSSSSSSSS$$$$$$$$$$

$$ BULK DATA CARDS 55

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

$

$ MISCELLANEOUS PARAMETERS

$$SSSSSSSSSSSSSSSSS$SSSSSSSS

S

PARAM,TINY, 0.999

PARAM,GRDPNT,0

PARAM,MAXRATIO,I.*I3

PARAM,COUPMASS,I

PARAM,WTMASS,0.00259

PARAM,AUTOSPC,YES

$

$ PARAMETERS FOR SOL 66

SSSSSSSSSSSSSSSSS$SSSSSS$

$

PARAM,LGDISP, I

NLPARM,100,2,,ITER, I

S

PARAM,TESTNEG,I

$

$ CENTRIFUGAL LOAD

$SSSSSSSSSSSSSSSSSS$

$

RFORCE, 1,0, ,11.,0.,0.,1.,2

$

$$SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS$SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS$

$$ ARTICULATED HUB CUFF AND BLADE ROOT: 4-8-92 $$

$$$$$$SSSS$SSSSSSSSSSS$SSSSSSS$$SSSSSSSSSSSSSSSS$SSSSSSSSSSSSS$SSS$$$$$$$$$$

$

$ .............................................

$ GEOMETRY:

$ ...........................................................

$ ..................................................................
$ GRID ID CP Xl X2 X3 CD PS SEID

$ ....... 2 ....... 3 ....... 4 ....... 5 ....... 6 ...... 7 ....... 8 ....... 9 ....... A .......

GRID, 200,, 3.00, 0.0, 0.0,, 1234

GRID, 201,, 6.87, 0.0, 0.0

GRID, 202,, 8.87, 0.0, 0.0

GRID, 203,, 10.625, 0.0, 0.0

GRID, 204,, 3.00, 0.0, 0.0,, 123456

S

$ ..............................................................................

$ CONNECTIVITY:

$ ..............................................................................

$ BLADE CUFF AND ROOT (RS 3.0 TO 12.5)

$ ............................................................................

$ CBEAM EID PID GA GB Xl X2 X3

$ ....... 2 ....... 3 ....... 4 ....... 5 ....... 6 ....... 7 ....... 8 ....... 9 ...... A

CBEAM 200 200 200 201 0.0 1.0 0.0

CBEAM 201 201 201 202 0.0 1.0 0.0

CBEAM 202 202 202 203 0.0 1.0 0.0

CBEAM 203 203 203 i000 0.0 1.0 0.0

$

$ LEAD-LAG DAMPER ELEMENT

$ ............................................................................

$ CELAS2 EID K G] C1 G2 C2 GE S

$ ....... 2 ....... 3 ....... 4 ....... 5 ....... 6 ....... 7 ...... 8 ....... 9 ..... A .......

CELAS2, 204, 464.0, 204, 6, 200, 6, 980.0

$

$ ...................................................................

$ PROPERTY CARDS:

S ....................................................................

$ ...............................................................

$ PBEAM PID MID A Ii I2 I12 J NSM

$ ....... 2 ....... 3 ....... 4 ....... 5 ....... 6 ....... 7 ....... 8 ....... 9 ....... A .......

PBEAM, 200, i000, 5.500, 0.5000, 0.5000, , 0.2632, 0.42511, +P2001

+P2001 ......... +P2002

+P2002 ..... 2.200-1

$

PBEAM, 201, i000, 0.371, 0.1500, 0.0500, , 0.1316, 0.19380, +P2011

+P2011 ......... +P2012

+P2012 ..... 4.826-2

S

PBEAM, 202, i000, 0.371, 0.0250, 0.0040, , 0.0105, 0.04086, +P2021

+P2021 ......... +P2022

+P2022 ..... 2.505-2

$

PBEAM, 203, i000, 0.371, 0.0250, 0.0040, , 0.0105, 0.15113, +P2031

+P2031 ......... +P2032

+P2032 ..... 5.671-2

5

S

555S5$555555555555$$$5555$555555555555555555555555555$$$55555555555555555555

$5 FREON RESEARCH BLADE, LIGHTLY BALLASTED ( RS 12.5 TO 55.0 ) 4-9-92 $5

5SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS555555$SSSSSSSSSSSS5555$5

S

S ..................................................................

$ GEOMETRY:

$ ..........................................................................

5 .......................................................................

5 GRID ID CP Xl X2 X3 CD PS SEID

5 ....... 2 ...... 3 ....... 4 ..... 5-- - 6 ..... 7 ....... 8 .... 9 --A --

GRID i000 12.500 0.000

GRID i001 13.000 0.000

GRID 1002 14.000 0.000

GRID 1003 15.000 0.000

GRID 1004 15.375 0.000

GRID 1005 15.600 0.000

GRID 1006 16.000 0.000

GRID 1007 17.000 0.000

GRID 1008 17.850 0.000

GRID 1009 18.000 0.000

GRID i010 19.000 0.000

GRID I011 20.000 0.000

GRID ]012 21.000 0.000

GRID 1013 22.000 0.000

0 000

0 000

0 000

0 000

0 000

0 000

0 000

0 000

0 000

0 000

0.000

0.000

0.000

0.000
GRID 1014 23.000 0.000 0.000

GRID 1015 23.750 0.000 0.000

GRID 1016 24.000 0.000 0.000

GRID 1017 25.000 0.000 0.000

GRID 1018 26.000 0.000 0.000

GRID 1019 27.000 0.000 0.000

GRID 1020 28.000 0.000 0.000

GRID 1021 28.250 0.000 0.000

GRID 1022 29.000 0.000 0.000

GRID 1023 29.150 0.000 0.000

GRID 1024 30.000 0.000 0.000

GRID 1025 31.000 0.000 0.000

GRID 1026 32.000 0.000 0.000

GRID 1027 33.000 0.000 0.000

GRID 1028 34.000 0.000 0.000

GRID 1029 35.000 0.000 0.000

GRID 1030 36.000 0.000 0.000

GRID 1031 37.000 0.000 0.000

GRID 1032 38.000 0.000 0.000

GRID 1033 39.000 0.000 0.000

GRID 1034 40.000 0.000 0.000

GRID 1035 41.000 0.000 0.000

GRID 1036 41.250 0.000 0.000

GRID 1037 42.000 0.000 0.000

GRID 1038 43.000 0.000 0.000

GRID 1039 44.000 0.000 0.000

GRID 1040 45.000 0.000 0.000

GRID 1041 46.000 0.000 0.000

GRID 1042 47.000 0.000 0.000

GRID 1043 48.000 0.000 0.000

GRID 1044 49.000 0.000 0.000

GRID 1045 50.000 0.000 0.000

GRID 1046 51.000 0.000 0.000

GRID 1047 52.750 0.000 0.000

GRID 1048 53.000 0.000 0.000

GRID 1049 54.000 0.000 0.000

GRID 1050 54.250 0.000 0.000

GRID 1051 55.000 0.000 0.000 S$ CBEAMEID PID GA S --2....... 3 -4..... 5

GB X1 X2 X3

--6.......7-8 ......9.......A-

CBEAM 1000 i000 i000 I001 0.0 1.0 0.0

CBEAM I001 I001 i001 1002 0.0 1.0 0.0

CBEAM 1002 1001 1002 1003 0.0 1.0 0.0

CBEAM 1003 i001 1003 1004 0.0 1.0 0.0

CBEAM 1004 1004 1004 1005 0.0 1.0 0.0

CBEAM 1005 1004 1005 1006 0.0 1.0 0.0

CBEAM 1006 1004 1006 1007 0.0 1.0 0.0

CBEAM 1007 1004 1007 1008 0.0 1.0 0.0

CBEAM 1008 1008 1008 1009 0.0 1.0 0.0

CBEAM 1009 1008 1009 I010 0.0 1.0 0.0

CBEAM i010 1008 i010 I011 0.0 1.0 0.0

CBEAM i011 1008 i011 1012 0.0 1.0 0.0

CBEAM 1012 1008 1012 1013 0.0 1.0 0.0

CBEAM 1013 1008 1013 1014 0.0 1.0 0.0

CBEAM 1014 1008 1014 1015 0.0 1.0 0.0

CBEAM 1015 1015 1015 1016 0.0 1.0 0.0

CBEAM 1016 1015 1016 1017 0.0 1.0 0.0

CBEAM 1017 1015 1017 1018 0.0 1.0 0.0

CBEAM 1018 1015 1018 1019 0.0 1.0 0.0

CBEAM 1019 1015 1019 1020 0.0 1.0 0.0

CBEAM 1020 1015 1020 1021 0.0 1.0 0.0

CBEAM 1021 1021 1021 1022 0.0 1.0 0.0

CBEAM 1022 ]021 1022 1023 0.0 1.0 0.0

CBEAM 1023 1021 1023 1024 0.0 1.0 0.0 CBEAM 1024 1021 1024 1025 0.0 1.0 0.0

CBEAM 1025 1021 1025 1026 0.0 1.0 0.0 CBEAM 1026 1021 1026 1027 0.0 1.0 0.0

CBEAM 1027 1021 1027 1028 0.0 1.0 0.0

9
CBEAM 1028 1021 1028 1029 0.0 1.0

CBEAM 1029 1021 1029 1030 0.0 1.0

CBEAM 1030 1021 1030 1031 0.0 1.0

CBEAM 1031 1021 1031 1032 0.0 1.0

CBEAM 1032 1021 1032 1033 0.0 1.0

CBEAM 1033 1021 1033 1034 0.0 1.0

CBEAM 1034 1021 1034 1035 0.0 1.0

CBEAM 1035 1021 1035 1036 0.0 1.0

CBEAM 1036 1021 1036 1037 0.0 1.0

CBEAM 1037 1021 1037 1038 0.0 1.0

CBEAM 1038 1021 1038 1039 0.0 1.0

CBEAM 1039 1021 1039 1040 0.0 1.0

CBEAM 1040 1021 1040 1041 0.0 1.0

CBEAM 1041 1021 1041 1042 0.0 1.0

CBEAM 1042 1021 1042 1043 0.0 1.0

CBEAM 1043 1021 1043 1044 0.0 1.0

CBEAM 1044 1021 1044 1045 0.0 1.0

CBEAM 1045 1021 1045 1046 0.0 1.0

CBEAM 1046 1046 1046 1047 0.0 1.0

CBEAM 1047 1047 1047 1048 0.0 1.0

CBEAM 1048 1048 1048 1049 0.0 1.0

CBEAM 1049 1049 1049 1050 0.0 1.0

CBEAM 1050 1050 1050 1051 0.0 1.0

S

0.0

0.0

0.0

0.0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

$ ..............................................................................

$ PROPERTY CARDS:

S ......................................................................

S ..............................................................................

S PBEAM PID MID A Ii I2 I12 J NSM

S ....... 2 ....... 3 ...... 4 - --5 ...... 6 ....... 7 ....... 8 ....... 9 ...... A .......

PBEAM, 1000,1000,0.377,0 03550,0.00394 ,0.03940,0.14048,+P001

+P001 ......... +P002

+P002 ..... 5.559-2 .... ÷P003

+P003, 0.00, 0.0, 0.00, 0 0

$

PBEAM, 1001,1000,0.386,0 02520 0.00249 ,0.00976,0.3134-I,+P011

+P011 ......... +P012

+P012 ..... 2.779-2 .... +P013

+P013, 0.00, 0.0, 0.00, 0 0

S

PBEAM,1004,1000,0.339,0 02520 0 00249 ,0.00976,0.4376-I,+P041

+P041 ......... +P042

+P042 ..... 2.961-2 .... +P043

+P043, 0.00, 0.0, 0.00, 0 0

$

PBEAM, 1008,1000,0.278,0 03040 0 00231 ,0.00674,0.4123-I,+P081

+P081 ......... +P082

+P082 ..... 2.888 2 .... +P083

+P083, 0.00, 0.0, 0.00, 0 0

S

PBEAM,1015,1000,0.249,0 02636 0 00181 ,0.00565,0.400-I,+P151

+PI51 ......... +P152

+P152 ..... 2.810-2 .... +P153

+P153, 0.00, 0.0, 0.00, 0 0

S

PBEAM, 1021,1000,0.224,0 02447 0 00151 ,0.00485,0.3903 I,+P211

+P211 ......... +P212

+P212 ..... 2.756 2 .... +P213

+P213, 0.00, 0.0, 0.00, 0 0

$

PBEAM, 1046,1000,0.247,0.02447,0 00151,,0.00485,0.3903-I,+P461

+P461 ......... +P462

+P462 ..... 2.756-2 .... +P463

+P463, 0.00, 0.0, 0.00, 0 0

$

PBEAM, 1047,1000,0.279,0.02448 0 00160,,0.00502,0.4125-I,+P471

+P471 ......... +P472

+P472 ..... 2.826-2 .... +P473

+P473, 0.00, 0.0, 0.00, 0.0

S

PBEAM, 1048,1000,0.305,0.05000,0.00500,,0.OI435,0.7867-1,+P481

÷P481 ......... +P482

+P482 ..... 3.984-2 .... +P483

10
+P483, -0.106, 0.0, -0.106, 0.0

$

PBEAM,1049,1000,0.099,0.04000,0.00400,,O.01148,0.607-1,+P491

+P491 ......... +P492

+P492 ..... 3.563-2 .... +P493

+P493, -0.17, 0.0, -0.17, 0.0

S

PBEAM, 1050,1000,0.05,0.00500,0.00050,,0.01435,0.1101 I,+P50]

+P501 ......... +P502

+P502 ..... 4.401-3 .... +P503

+P503, -0.940, 0.0, -0.940, 0.0

$

$ ......................................................................

$ MATERIAL PROPERTY CARDS:

$ .........................................................................

$ i000: FIBERGLASS BLADE (ASSUMED PROPERTIES)

$ ........................................................................

$ MID E G NU RHO

$ ....... 2 ....... 3 ...... 4 ..... 5 ....... 6 ....... 7 ....... 8--- 9- -A ....

MAT1 i000 1.0+7 0.3

S

$

ENDDATA

II
Appendix B

MSC/NASTRAN Solution 63 Restart Data Deck

This appendix presents the executive control cards and the case control cards required to execute the solution 63

runs.

RESTART

(use this executive control section for MSC/NASTRAN version 66 or 67:)

S

$$SSSSSSSSSSSSSS$$S$$SSSSSSSSSSSSSS$S$$SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS$

$$ EXECUTIVE CONTROL CARDS 55

$SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS$$$$$$$$$

$

ID ATR-L, WKW

SOL 63 $ NORMAL MODES DATABASE V. 66B

TIME 20

S

$ RECOMPILE SOL 63 TO INCLUDE ALTERS (MSC/NASTRAN VERSIONS 66 AND 67)

SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS$

$

COMPILE SOL63 SOUIN=MSCSOU NOLIST NOREF $

S

ALTER 193 $

FILE EST=OVRWRT/GEI=OVRWRT/GPECT:OVRWRT/KELM=OVRWRT/KDICT=OVRWRT $

S

RFALTER RF63D89

S

$ INCLUDE GYRO TERMS

SSSSSSSSSSSSSSSSSSS$$$

S

INCLUDE 'NLGYRO.ALT'

S

CEND

(use this executive control section for MSC/NASTRAN version 68:)

SSSSSSSSSSSSSSSSSSSSS$SSSSSSSSSSSSSSSSSSSSSSSSSSSSS$SSSS$$$SSSSSSSSSSSSSSSS$

S$ EXECUTIVE CONTROL CARDS 55

$$$SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS$SSSSSSSSSSSSSSSSSSSSSSSS$

S

ID ATR-L, WKW

SOL 63 $ NORMAL MODES DATABASE V. 66B

TIME 20

$

$ RECOMPILE SOL 63 TO INCLUDE ALTERS (MSC/NASTRAN VERSION 68)

$$$$$$$SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS

$

COMPILE SOL63 SOUIN:MSCSOU NOLIST NOREF $ NOLIST NOREF $

$

RFALTER RF63D89

$

$ INCLUDE GYRO TERMS

$SSSSSSSSSSSS$SSSSSSS$

S

INCLUDE 'NLGYRO.ALT'

$

CEND

S

(remaining sections are the same for all versions of MSC/NASTRAN)

$

SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS$SSSSSSSSSSSSSSSSSSSSSSSSSS$

$$ CASE CONTROL CARDS $$

$$$SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS$

$

TITLE=FRB (LIGHT BALLAST) ON ARTICULATED HUB

12
LABEL:(CF LOAD ii HZ ROTATION)

SUBTITLE- NORMAL MODES RESTART SOL 63

$

ECHO=BOTH

DISPLACEMENT=ALL

OLOAD=ALL

s

SEALL=ALL

$

LOAD-I

S

METHOD-10

S

BEGIN BULK

S

S

$SSSSSSSSSSSS$$SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSsss$

$$ BULK DATA CARDS S$

$$$$$$$SSSSS$$$$$$$$$$$$SSSSSSSSSSSSSSSSSSS$SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS$

$

$ MISCELLANEOUS PARAMETERS

SSSSSSSSSSSSSSSSS$SSSSSSSSSS

$

PARAM

PARAM

PARAM

PARAM

PARAM

PARAM

$

TINY,0.999

GRDPNT,0

MAXRATIO, I.+I3

COUPMASS,I

WTMASS,0.00259

AUTOSPC,YES

$ PARAMETERS FOR SOL 63

$SSSSSSSSSSSSSSSSSSSSS$$$

S

PARAM,LGDISP, Z

PARAM,LOOPID, 2

$

PARAM,TESTNEG,I

$

$ EIGENVALUE EXTRACTION METHOD FOR SOL 63 RESTART

sssassssssssssssssssssssssssssssssssssssssssssssss$

S

EIGR, Z0,SINV,0.,100.

S

S CENTRIFUGAL LOAD

$SSSSSSSSSSSSSSSSSSS

$

RFORCE, Z,0,,11.,0.,0.,1.,2

S

(model definition bulk data omitted; same as solution 66 deck)

$

ENDDATA

13
Appendix C

Modifications to NLGYRO.ALT for Use With MSC/NASTRAN Version 68

Much of the DMAP language was changed between MSC/NASTRAN Version 68 and earlier versions. Because of

this change, two minor changes in the original version 66b NLGYRO.ALT DMAP source code (obtained from MSC)

are required for it to execute properly under MSC/NASTRAN version 68. These modifications follow.

1. In line 1 (ignoring comments), change

ALTER 492 $

to

ALTER 504 $

2. In line 23, change

VECPLOT , ,BGPDT, EQEXIN, CSTM, 'RBGLOBAL///4/ $

to

VZCPLOT ,,BGPDT,EQZX_N,CSTM,, ,/RBCr.OSAL///4/ S

(i.e., add two commas after CSTM.)

14
References

1. Anon.: MSC/NASTRAN User's ManuaI--MSC/NASTRAN Version 66. MacNeai-Schwendler Corp., 1988.

2. Joseph, Jerrard A., ed.: MSC/NASTRANApplication Manual--

MSC/NASTRAN Version 66A. MacNeal-Schwendler Corp.,

1991.

3. Mack, Wayne V., ed.: MSC/DYNA Theoretical Manual--MSC/

DYNA Version 1. MacNeal-Schwendler Corp., 1989.

4. Lee, Sang H., ed.: Preliminary MSC/NASTRAN Handbook for

Nonlinear Analysis. MacNeal-Schwendler Corp., 1991.

5. Lawrence, Charles; Aiello, Robert A.; Ernst, Michael A.; and

McGee, Oliver G.: A NASTRAN Primer for the Analysis of

Rotating Flexible Blades. NASA TM-89861, 1987.

6. McGee, Oliver G.: Finite Element Analysis of Flexible, Rotating Blades. NASA TM-89906, 1987.

15


Form Approved

REPORT DOCUMENTATION PAGE OMBNo.0704-0188

Publicreportingburdenforthis colleoticnof informationis estimatedto average1 hourper response,includingthe timefor revlew4nginstructions,searchinge0dstingdatasources,

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DavisHighway,Suite1204, Arlington,'CA22202-4302, andto the Officeof Managementand Budget,PaperworkReductionProject(0704-0188),Washington,DC 20503.

1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

June 1997 Technical Memorandum

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

Rotating Shake Test and Modal Analysis of a Model Helicopter Rotor Blade

6. AUTHOR(S)

W. Keats Wilkie, Paul H. Mirick, and Chester W. Langston

7. PERFORMINGORGANIZATIONAME(S)ANDADDRESS{ES)

NASA Langley Research Center Vehicle Technology Center

Hampton, VA 23681-0001 U.S. Army Research Laboratory

NASA Langley Research Center

Hampton, VA 23681-0001

9. SPONSORING/MONITORINGAGENCYNAME(S)ANDADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

and

U.S. Army Research Laboratory

Adelphi, MD 20783-1145

WU 505-63-36-02

A5008

8. PERFORMING ORGANIZATION

REPORT NUMBER

L-17352

10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

NASA TM-4760

ARL-TR-1389

11. SUPPLEMENTARY NOTES

Wilkie, Mirick, and Langston: Vehicle Technology Center, ARL, Langley Research Center, Hampton, VA.

12a. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified-Unlimited

Subject Category 05

Availability: NASA CASI (301) 621-0390

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

Rotating blade frequencies for a model generic helicopter rotor blade mounted on an articulated hub were experimentally determined. Testing was conducted using the Aeroetastic Rotor Experimental System (ARES) testhed in

the Helicopter Hover Facility (HHF) at Langley Research Center. The measured data were compared to pretest analytical predictions of the rotating blade frequencies made using the MSC/NASTRAN finite-element computer

code. The MSC/NASTRAN solution sequences used to analyze the model were modified to account for differential

stiffening effects caused by the centrifugal force acting on the blade and rotating system dynamic effects. The correlation of the MSC/NASTRAN-derived frequencies with the experimental data is, in general, very good although

discrepancies in the blade torsional frequency trends and magnitudes were observed. The procedures necessary to

perform a rotating system modal analysis of a helicopter rotor blade with MSC/NASTRAN are outlined, and complete sample data deck listings are provided.

14. SUBJECT TERMS

Helicopters; Model rotor testing; Rotor analysis; NASTRAN; Structural dynamics

17. SECURITY CLASSIFICATION

OF REPORT

Unclassified

NSN 7540-0%280-5500

18. SECURITY CLASSIFICATION

OF THIS PAGE

Unclassified

15. NUMBER OF PAGES

16

16. PRICE CODE

A03

19. SECURITY CLASSIFICATION 20. LIMITATION

OF ABSTRACT OF ABSTRACT

Unclassified

Standard Form 298 (Rev. 2-89)

Prescribedby ANSI Std.7--39-18

298-102