1 ucb, may 04, 2005 magnetometer booms vibration issues berkeley composites laboratory department of...
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1 UCB, May 04, 2005
Magnetometer BoomsVibration Issues
Berkeley Composites Laboratory
Department of Mechanical Engineering
University of California at Berkeley
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