1 UCB, May 04, 2005

Magnetometer BoomsVibration Issues

Berkeley Composites Laboratory

Department of Mechanical Engineering

University of California at Berkeley

2 UCB, May 04, 2005

Overview

3 UCB, May 04, 2005

Deployment

FGB stowed

SCB stowed

FGB deployed on gravity offset fixture

SCB deployed on gravity offset fixture

4 UCB, May 04, 2005

Deployment

1) Frangibolts Actuated

3) Mid-deployment2) Elbow DAD Releases

4) Fully Deployed

5 UCB, May 04, 2005

Vibration Testing (PER slide)

Date Result Corrective Actions

2/28/05 Mounting bolts for SCB DAD tower not torqued properly. SCB DAD tower failed in Y axis.

Use torque-limiting screwdriver with extension driving bits.

3/02/05 Fatigue damage observed (between tests) in SCB base bracket’s near foot,

Add fillet to corner of near foot to reduce stress concentration.

3/07/05 Fatigue damage observed (between tests) in SCB base bracket’s near foot above fillet.

Add fillets to corner of both feet to reduce stress concentration. Add larger steel washers and G10 isolators to completely support feet.

3/11/05 Deformation observed (between tests) in SCB base bracket’s far foot.

Retrofit base with wider feet.

3/23/05 Fatigue damage observed in SCB DAD tower’s feet. Replaced with redesigned DAD tower with wider feet.

3/29/05 Booms complete vibration qualification and are tested in TV to determine functionality at hot and cold extremes. SCB has increased friction. FGB has loss of preload in frangi-bolt ring from stripped threads in frangi-bolt ring (Build/Test Mistake)

Add deployment testing after vibration and before TV testing.

Tightened spool to holds the base spring subassembly.

4/08/05 5% Frequency shift with no visible damage. SS washers added to (non-load bearing) surfaces to eliminate observed fretting.

4/25/05 Similar frequency shift in SCB after first X random test.

Abnormal frequency response caused by G10 spacers.

Booms survived structurally but increased friction was noted during subsequent deployment.

Frequency response stable after second random vibration • G10 spacers were removed prior to continuing with vibration • Lubrication and improvement of rubbing surfaces • Offloading force incorrect during deploy. Booms deploys when offload corrected.

6 UCB, May 04, 2005

SCB Base Bracket

Fatigue crack in near foot Fatigue crack in near foot still appear (not clearly shown)

Round off corners. Repeat

vibration.

Use larger washers to better

support feet. Repeat

vibration.

Machine off existing feet and retrofit

wider feet. Repeat vibration.

Near foot has no damage; Yielding in far foot

Base bracket with retrofitted

feet has no damage.

7 UCB, May 04, 2005

Base Hinge Fretting/ Galling

Bronze spool captures base spring.

Non-load bearing (vertical direction)

Alodine aluminum clevis

Steel washer between clevis and bronze spool

(only lower washer visible in picture.)

FGB and SCB share common hinge mechanism

8 UCB, May 04, 2005

Base Hinge Fretting/ Galling

Clevis inside surfaces

Steel washers

Bronze spring spool

Steel washer on

clevis

Steel washer and bronze spring spool

9 UCB, May 04, 2005

Frequency shift

Frequency shifts without damage to instrument after random vibration.

G10 thermal isolators Missing chamfer (machining error) causes binding of upper stop and clevis.

10 UCB, May 04, 2005

F1 random vibration

FGB SCB

X (min.)

Y (min.)

Z (min.)

X (min.)

Y (min.)

Z (min.)

2/28/05 2 2 2

3/2/05 2 2 2

3/7/05 2

3/11/05 2

3/23/05 2 2

3/25/05 2 2 2

4/8/05 2 2

4/25/05 6 2 2 4 2 2

Subtotal 10 4 4 16 10 4

Total 18 minutes 30 minutes

F1 booms re-designated F6 flight spare because of the accumulated random vibration time

11 UCB, May 04, 2005

Random Vibration Specs

Random Vibration Levels (Ref. Swales SAI-TM-2430-Rev D )

TEST RESPONSE X axis Y axis Z axis

@ FGM Sensor 30.4 Grms 36.4 Grms 27.8 Grms

@ SCM Sensor 27.3 Grms 20.6 Grms 21.5 Grms