Magnetometer Booms Vibration Issues Berkeley Composites Laboratory Department

Magnetometer Booms Vibration Issues Berkeley Composites Laboratory Department of Mechanical Engineering University of California at Berkeley 1 UCB, May 04, 2005

Overview 2 UCB, May 04, 2005

Deployment FGB stowed FGB deployed on gravity offset fixture SCB stowed SCB deployed on gravity offset fixture 3 UCB, May 04, 2005

Deployment 1) Frangibolts 2) Elbow Actuated Releases DAD 3) Mid-deployment 4) Fully Deployed 4 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 G 10 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 G 10 spacers. Booms survived structurally but increased friction was noted during subsequent deployment. Frequency response stable after second random vibration • G 10 spacers were removed prior to continuing with vibration • Lubrication and improvement of rubbing surfaces • Offloading force incorrect during deploy. Booms deploys when offload corrected. 5 UCB, May 04, 2005

SCB Base Bracket Use larger washers to better support feet. Repeat vibration. Round off corners. Repeat vibration. Fatigue crack in near foot still appear (not clearly shown) Fatigue crack in near foot Machine off existing feet and retrofit wider feet. Repeat vibration. Near foot has no damage; Yielding in far foot 6 Base bracket with retrofitted feet has no damage. UCB, May 04, 2005

Base Hinge Fretting/ Galling Alodine aluminum clevis FGB and SCB share common hinge mechanism Steel washer between clevis and bronze spool (only lower washer visible in picture. ) 7 Bronze spool captures base spring. Non-load bearing (vertical direction) UCB, May 04, 2005

Base Hinge Fretting/ Galling Clevis inside surfaces Steel washer on clevis Steel washer and bronze spring spool Bronze spring spool 8 UCB, May 04, 2005

Frequency shifts without damage to instrument after random vibration. G 10 thermal isolators Missing chamfer (machining error) causes binding of upper stop and clevis. 9 UCB, May 04, 2005

F 1 random vibration FGB X (min. ) 2/28/05 2 Y (min. ) SCB Z (min. ) X (min. ) 2 3/2/05 Y (min. ) Z (min. ) 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 4/25/05 6 2 2 4 2 2 Subtotal 10 4 4 16 10 4 Total 2 18 minutes 30 minutes F 1 booms re-designated F 6 flight spare because of the accumulated random vibration time 10 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 11 UCB, May 04, 2005