ACCEPTANCE DATA PACKAGE

NASA CONTRACT NAS8-39409

SXI STEPPER MOTOR/ENCODER

AEROFLEX PIN 16187

D - STRENGTH ANALYSIS

F

https://ntrs.nasa.gov/search.jsp?R=19980211390 2020-04-09T19:01:31+00:00Z

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SECTION D

STRENGTH ANALYSIS

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/ EROFLEXLABORATORIES 35South ServiceRoad. PJainview,NY 11803

TEL:516-694-6700.FAX:516-694-6771

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STRENGTH ANALYSIS REPORT

FLIGHT READINESS REVIEW (FRR)

for

SXl STEPPER MOTOR/ENCODER

Prepared byAeroflex Laboratories

Farmingdale New York

for

NASA - MSFC

In Accordance with MSFC-HDBK-505A

Summary_

The strength analysis report for FRR shall include only revisions to update the strength

analysis reports for the flight design configuration. Since there have been no revisions tothe design configuration since the PDR and the CDR this report shall consist of re-

submitting the analysis previously performed.

In addition the motors have been subjected to Sine vibration, Random vibration, and

shock per the SXI specification. Both motor/encoders have passed all three tests. Therewas no evidence of damage to the motor/encoder and the motor/encoder performed asrequired by the Acceptance test procedure. No degradation was seen between the beforeand after performance tests. The testing verified the analysis that there were adequate

safety margins with regard to structural integrity. Separate reports are available from the

test facility and are apart of the FRR submittal.

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STEPPER MOTOR/ENCODER

SOLAR X-RAY IMAGER (SXI)

STRESS ANALYSIS

(ARX PIN 16187)

March 16, 1994

I_EROFU_X----J

SXl STEPPER MOTOR/ENCODER

VIBRATION STRESS ANALYSIS

EXTRACT

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An FEA stress analysis was performed on the Aerofiex design to assure that the motor

will withstand the random vibration spectrum shown in Figure 11. The program used wasALGOR with updated releases to 5/21/93. The results are tabulated in Table I. Constants

and values used for the analysis are listed in Table II.

The analysis focused on:

* ... The Housing (with special regard paid to the three mounting posts). A slug

of dense matedal was cantilevered from the beadng mounting surface to simulate an

unbalanced load on the mounting screws equaling the rotor weight. (It was necessary touse this simplified load and not use the actual rotor model so as not to exceed the disk

space required for temporary storage files in the FEA processing). The housing wasconstrained on the inner surface of the mounting holes to simulate the insert contact area.

All other volume was free to move in 6 axes (three translation and three rotation).

* ... The Rotor with encoder disk. The assembly was constrained on the outerbearing surface area.

* ... The large PC Board with tantalum shields attached in their 4 locations. The

PC Board was constrained on the inner surface of the 4 mounting holes.

* ... The stress introduced by the shrink fit of the bearing liner in the housing.The outer housing was heated to +71C and the insert cooled to -40C. The stress was

measured at 0 degrees C.

The vibration energy was applied in the x direction and in the y direction independently.

The summary of results is shown in Table I.

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CONCLUSIONS

The stress induced by vibration and thermal differentials were within the material linearratings. However, the shrink fit of the bearing retainer sleeve into the housing wasdeemed to be too tight. It was necessary to press fit the two sections even attemperature. The fit now has a 2 tenths clearance at temperature. The stress reflectedin the Figure 6 reflect this change.

The design is satisfactory and no further changes are necessary.

* Please note that figure displacements are highly exaggerated to make the smalldisplacements visible.

* Not all stress and displacement results were plotted but they are shown in Table I

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T_EI

ITEM DESCR IPT ION

1) ROTOR/ENCODER

D ISC

2) HOUSING

3) PC BOARD

I) ROTOR/ENCODER

DISC

2) HOUSING

3) PC BOARD

I) ROTOR/ENCODER

DISC

213 HOUSING

3) F'C BOARD

RESONANCE (Fund)

1096 Hz (rotary)

1238 Hz (X & Y)

25c)9 Hz

1240 Hz

X VIBRATION

MAX STRESS (PSI) MAX DISP (IN)

0.94 (ROTARY)

0.187 (X)

211

11.9

Y VIBRATION

9.8E-8

1.7E-8

7.9E-5

6.4E-6

O. 0012 (ROTARY)

1442 (Y)

1.2

11.4

1.2E-IO

1.3E-4

4.5E-7

6.4e-6

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MATERIAL

ALUMINUM

STEEL

BeCu

G10 EPOXY

TANTALUM

SIM WGT(HSG)

TABLE II

DENS ITY

O. 11 LBS/IN"3

O. 29

O.29B

O.065

0.6

5.5

YOUN(_SMOV

IOE6 PSI

29E6

18.5E6

22E5

27E6

29E6

LIN EXP

23.4E-6 IN/IN/C

I0.6E-6

N/A

N/A

N/A

N/A

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ADDENDUM: Response to NASA 3/30/94 comments on stress analysis

for the SXI motor.

Additional analysis added static loads, ,:ombined loads and sine

vibration to the existing random vibration analysis.

Tile stress and displacement calculations are performed by the

ALGOR FEA program. The ALGOR program allows the excitation of

static accelerations in each of three axis or combinations of

these axis to be applied to the model. This feature was used to

determine the stresses and displacements for the static and

combined loads. Tile program also allows a single frequency at a

given acceleration be applied to the model in any of three axis.

This feature was used to apply the sinusoidal excitation to the

models.

The models were created using the dimensions of tile drawing and

were decoded into, 3 dimensional "bricks" for the finite element

analysis.

The rotor and hub assembly was constructed with a manual mesh to

control densities so that reasonable computer space was available

for calculation. The model was constrained at tile bearing

surface which prevented rotational or translational motion. All

vibration inputs were relative to this base.

The Housing was constrained at the inner surface of the three

mounting holes. A dense weight was cantilevered off the outer

bearing surface to produce moments which would be applied by the

actual rotor and stator during vibrations and accelerations.

The PC board was constrained at the inner surface of the 4

mounting holes. The tantalum shields were mounted to the pc

board and IC's as shown in the drawings.

A series of 4 Tables show the type excitation, stress, displace-

ment, yield strength used for the analysis, Safety factor used,

safety margin between stress produced and yield strength reduced

by the safety factor. (ie (yield strength/safety factor)/stress

induced:l)

The material properties are shown in Table II of the original

r epc,rt.

Not every combination of load or every type of axis excitation

was calculated because inspection of the data shows that the

device is clearly well within yield limits with large safety

margins for the materials and configurations designed. E.G. 14.7

G's was used for every axis in the analysis and not reduced as it

could have been for the other axes. The displacements seen will

be well clear of hitting other adjacent structures. In

addition, the motor/encoder will undergo vibration testing.

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