Axial Safety Clip System FDR

Transcription

1 Axial Safety Clip System FDR Steven Bauman Brian Cuerden Kurt Kenagy Lotis Page 1

2 Axial Safety Clip Outline Puck Bond Test Results Justification Requirements Components Axial Safety Clip System Lotis Mirror Bonds Load experienced by the system Forces applied to the clips Installation Procedure Bonding Procedure Final Procedure Thermal effects Load Transfer Conclusion Questions from LMSSC Page 2

3 Puck Bond Test Results RELATIVE AXIAL DISPLACEMENT (microns) MAG-I, P266, 70 lbf MMT, WS76, 160 lbf MMT, WS25, 70 lbf LBT-I, P359, 70 lbf LBT-I, P500, 160 lbf LMMSSC-MSO LOTIS PROJECT AXIAL CREEP OF WITNESS PUCKS UNDER PURE AXIAL LOAD F, 17-24% RH /6/03 0:00 10/26/03 0:00 11/15/03 0:00 12/5/03 0:00 12/25/03 0:00 1/14/04 0:00 2/3/04 0:00 2/23/04 0:00 ELAPSED TIME Test Data shows a vital need to prevent axial creep rupture of the bonds. Page 3

4 Purpose Justification The Lateral safety clip system cannot offload axial forces, therefore the puck bonds must still resist axial forces. The puck bonds experience axial forces to counteract the overturning moment of the primary mirror. The Axial force on the pucks vary during operation, as the axial actuators are adjusted to correct the figure to the primary mirror. The pucks bonded to the bottom area of the back plate see a complimentary force of axial compression. Axial Safety Clip Implication Design Features: The Axial Safety Clip System will share the axial force on the collimator puck bonds. This prevents axial creep-rupture of the bond. Page 4

5 Requirements Summary of requirements The Maximum Stress in the glass must be less than 100psi. The Axial Safety Clips need to hold 5X the maximum load experienced by the load spreader. The Axial Safety Clip System must meet the 10 year delivery lifetime. All hardware must be stainless steel and blind holes and screws must be vented The epoxy used for bonding the mounting blocks to the mirror must be Scotch-weld 2216 B/A Gray High peel and shear strengths The RTV used for adhesion between the Axial clips and the retaining blocks must be Dow-Corning Q Viscous Relatively compliant Page 5

6 Axial Safety Clip Components Page 6

7 Axial Safety Clip System The Axial Safety clip system will be installed on 44 pucks total, 2x long double-puck loadspreaders, 8x short double-puck loadspreaders, 2x type A triple-puck loadspreader s, 2x type B triple-puck loadspreaders and 6x single-pucks. Page 7

8 Axial clip through the mirror The Axial Safety Clip mounting blocks are bonded to the mirror over the hex core ribs to minimize stresses in the mirror, as shown to the left. Page 8

9 Modified Axial Safety Clip System installed on a single-puck Page 9

10 Special Axial Safety Clip System Installed on a short double-puck loadspreader In order to locate the Epoxy bonding surface over a hex core rib and insure clearance under the loadspreader leg, special mounting blocks and retaining blocks were required to accommodate locations on the edge of the mirror. Page 10

11 Special Axial Safety Clip System Details Page 11

12 Axial Safety Clip Locations Loadspreaders and Pucks that require Axial Safety Clips. Loadspreader and puck numbers located on the back of the primary mirror. Page 12

13 Force applied to the loadspreader The Worst case nominal axial actuator force applied to a loadspreader is F axial = 120 lb The axial corrective force F corr = 67 lb F axial max = 187 lb Distributing the forces to each puck results in F max/puck = 93.5 lb Page 13

14 Applied loads to the Clip The Axial Safety clips are designed to compensate for the RTV puck bond failure data. The reaction forces shown are the loads that the epoxy bonds would experience if the RTV puck bond already in place was ignored. Page 14

15 Mirror Stress plot on backplate Page 15

16 Mirror stress plot inside cores Page 16

17 Analysis of the RTV Bond and Slope Deflection The RTV adhesive thickness must be calculated to match the correct compliance and stiffness to hold the load applied to the pucks. The Retaining Block and Axial clip bonding surfaces must be parallel during operation in order to keep uniform adhesive thickness on the edges on the bond. And to insure the load is uniformly applied to the adhesive area. Page 17

18 The RTV adhesive thickness calculated to hold the load applied to the pucks and remain less than the determined creep from the Puck Test data was determined to be.010 thick This will insure the 10 year collimator life. RTV Displacement over Time Page 18

19 Axial Safety Clip and Retaining Block To insure that the calculated.010 thick RTV bond remains uniform after a load is applied to the pucks, deflection slopes of the axial clip and retaining block must match. Page 19

20 Axial Deflection and Slope The slopes match to within.001 of an inch/inch insuring the RTV bond will remain uniform across the entire adhesion surfaces. The most the puck can creep now before the Safety clips take the entire puck load is.0035, which is half of the.006 puck creep rupture to failure criteria. Page 20

21 Bonding Procedure The Invar mounting blocks will be bonded to the mirror using a.005 thick 3M Scotch-weld epoxy adhesive over the hex core ribs. Nylon spacers will be fabricated and used to achieve the correct spacing between the mounting block and the cup and puck Page 21

22 Installation Procedure Once the Epoxy bond has had adequate time to form a full cured bond, the axial clips will be installed to the top of the cups using vented hardware. The epoxy adhesive takes 1-2 hours to form a partial bond and 7 days to form a fully cured bond. Page 22

23 Final Procedure After the axial clips are bolted to the cups, measurements will be made; and shim thickness will be determined to achieve a.010 thick bond. The retaining blocks will then have RTV adhesive applied to them and will be bolted down to the mounting blocks. Page 23

24 Thermal Effects, Stiff Safety Clip Stiffness of safety clip < 120,000 Lb/in Differential axial thermal growth ~ 39 -in/ F Force change = 120,000* 39 -in/ F = 4.68 Lbs / F Distortion change = 0.2 nm-rms WF/ F (after focus correction) The stiff safety clip is the 1/8 disk and a bonded invar block. The intent is to limit puck creep by providing a parallel load path throught the invar blocks. Page 24

25 Stiff Clip, Load Transfer Creep Rates Puck at 70 Lb load = 1400 to 431 -in/year measured 40 -in/year predicted Safety clip at 70 Lbs elastomer 20 -in/year predicted elastomer 152 -in/year predicted Load transfer time: Elastic deflection of clip is 70/120,000 = 588 -in Time to load clip to 70 lbs >> 0.42 years Estimated time is 0.4 to 1.4 years Range is based on variation of test creep rates Creep of the compressed elastomer layer in the clip is assumed negligible compared to the deformation required to elastically load the clip. WF distortion change is ~ 0.9 nm-rms (after 16 mode correction based on 70 Lb change/puck over 32 pucks). Page 25

26 Conclusion and Schedule Puck Bond Test Data establishes a need for an Axial Support System. The Safety Clip System meets all of the requirements desired. Primary Mirror Stress (FEA) has been performed, is complete, and acceptable. Analysis of impact to wavefront error shows negligible effect from load sharing between pucks and axial safety clips. The Design of the Safety Clip System is finished. All Assemblies and Parts have been detailed, and are being sent out for fabrication Axial saf ety clips Activ ity Name Start Date Finish Date % Complete Dec Jan Feb Mar Apr May Jun Design axial saf ety clip sy stem 12/15/03 1/28/ % Design axial saf ety clip sy stem Perf orm analy sis an ev aluate impact to primary mir 1/2/04 1/8/ % Perf orm analy sis an ev aluate impact to primary mirror Detail axial saf ety clip assemblies 1/29/04 2/9/ % Detail axial saf ety clip assemblies Fabricate axial saf ety clip assemblies 2/10/04 2/20/ % Fabricate axial saf ety clip assemblies Install axial saf ety clips on primary mirror 2/23/04 2/27/04 0.0% Install axial saf ety clips on primary mirror Dec Jan Feb Mar Apr May Jun Page 26

27 References Brian Cuerden and Steven Bauman, Safety Clip System Design Concept, File: safety clip PDR ppt Brian Cuerden and Steven Bauman, Safety Clip System Design Concept, File: LOTIS SOLM.ppt Brian Cuerden and Steven Bauman, Safety Clip System Design Concept, File: safety clip MDR ppt Brian Cuerden and Steven Bauman, Safety Clip System Design Concept, File: safety clip FDR ppt Kurt Kenagy Randy Lutz Steve Miller Blain Olbert, LMSSC-MSO LOTIS COLLIMATOR PROJECT, MIRROR PUCK BOND & RTV TESTING,STATUS REPORT & RESULTS SINCE 03/04/03 GROUP TELECON, PowerPoint Summary, 04/25/03, File: LOTIS_PUCKTEST_UPDATE_03.ppt Blain Olbert, LMSSC-MSO LOTIS COLLIMATOR PROJECT, MIRROR PUCK BOND & RTV TESTING,STATUS REPORT & RESULTS SINCE 05/01/03 GROUP TELECON, PowerPoint Summary, 04/25/03, File: LOTIS_PUCKTEST_UPDATE_04.ppt Page 27

28 Questions Page 28