ETM STRUCTURAL DESIGN SUMMARY FEA OF PROPOSED ETM STRUCTURE

ETM STRUCTURAL DESIGN SUMMARY FEA OF PROPOSED ETM STRUCTURE ANSYS Workbench (ANSYS University Advanced) version 9.0 LIGO-G050187-00-Z Information also covered in LIGO-T040214-DRAFT March 22nd 2005 Calum Torrie, Tim Hayler, Russell Jones, Mike Perreur-Lloyd, Janeen Romie, Dennis Coyne, Caroline Cantley, Norna Robertson, Larry Jones, Mike Gerfen and Justin Greenhalgh LIGO-G050069-00-D

Layout of the Controls prototype 2005 mm 710 mm x 550mm 440 mm x 440 mm LIGO-G050069-00-D

REQUIREMENTS The first resonance limits, including structural and non structural mass, and assuming a perfectly rigid support: 200 Hz first resonance for the upper structure 100 Hz Lower structure 100 Hz combined upper and lower structure Initially confirmed by FEA with a 15% contingency, later confirmed by prototype testing. LIGO-G050069-00-D

Cf. 418 kg from LIGO-T030137 MASS BUDGET UPPER TOP MASS, 22 kg x 2 (S) » Tablecloth etc (NS) » Top Stage (NS) » Ring (NS) » UPPER STRUCTURE 44 kg 15 kg 25 % C 19 kg 24 kg 25 % C 5 kg 100 % C 10 kg 37 kg 25 % C 46 kg 30 kg LOWER » UI MASS, 22 kg x 2 (S) » PEN MASSES, 40 jg x 2 (S) » TEST MASSES, 40 kg * 2 (S) » CLAMPING etc, 23 25 % C (NS) » Ring (NS) 5 kg 100% » Lower Structure (NS),23 kg 25% C 44 kg 80 kg 80 kg 29 kg removable ? 10 kg 29 kg TOTAL 422 kg OVERALL NON-SUSPENDED MASS inc. STRUCTURE 140 kg Actual Non-suspended mass inc. Structure 133 kg LIGO-G050069-00-D

Designing for vacuum Full penetration welds, avoids trapped volumes. No mating surface areas that trap residue from cleaning process. Welding method TIG, full penetration welds requires back gassing technique, labour intensive. Looking into possibility of dip brazing. Nitronic 60 thread inserts to inhibit wear, dust and galling. All holes to be through holes, LIGO-T040111-00-D Grade of Aluminium 6061-T6 is acceptable with respect to outgassing requirements, reference LIGO vacuum compatible materials list, LIGO-E960050-B-E. LIGO-G050069-00-D

Beams and Shells Upper structure example Box structure, 1st mode 90 Hz. LIGO-G050069-00-D Box structure with plates, 1st mode 118 Hz. Truss structure, 1st mode 240 Hz

ETM STRUCTURES CAD MODELS LIGO-G050069-00-D

Solid model FEA Clamping, Meshing, Convergence & Comparison CLAMPING » Surface fixed » 10-14 point locations » 4 corners 235 Hz and 252 Hz 215 Hz and 228 Hz 188 Hz and 202 Hz MESH » in general basic mesh with 50,000 elements. Had to use 120,000 elements for overall structure. Assumes complete connectivity, welded structure. Defeaturing the model such as rounds and holes. CONVERGENCE Increase number of elements until solution converges » work in process to cover this using reference LIGO-T030044 COMPARISON Solid model with beams and shells model ALGOR and ANSYS Comparative analysis LIGO-G050069-00-D

GOAL: - 200 Hz 15% contingency UPPER STRUCTURE 14 fixed supports around the ledge. 1st mode 214 Hz 2nd mode 217 Hz Mass 84 kg; # of elements 26,000; clamping at 14 points, same as the overall structure. LIGO-G050069-00-D NOTE: - Comparative analysis done in ALGOR!

GOAL: - 100 Hz 15% contingency LOWER STRUCTURE # of elements 45,000 Clamping method, fixed support on ring surface. 1st mode 130 Hz 2nd mode 131 Hz Mass 50 kg LIGO-G050069-00-D NOTE: - Comparative analysis done in ALGOR!

Overall Structure Modeling Tying together the Upper and Lower structure models we have a structure below the requirement of the mass budget with a 1st resonance of 85 Hz. Model Notes Mass 133 kg Nodes 115,000 Elements 57,000 1st Mode 85 Hz (long.) 2nd Mode 94 Hz (trans.) 3rd Mode 144 Hz (tors.) Fixed at 14 points around the top of the structure LIGO-G050069-00-D

Potential Improvements By adding more stiffening members to both the Upper and Lower Structure we have been able to increase the first mode to above 100Hz, however we now are over the mass budget requirement. Plates Added Model Notes Mass 140 kg Nodes 125,000 Elements 62, 000 1st Mode 103 Hz (long.) 2nd Mode 108 Hz (trans.) 3rd Mode 178 Hz (tors.) Fixed at 14 points around the top of the structure LIGO-G050069-00-D X-Brace Added Lower Structure Stiffeners

Future Plans TWO STRUCTURES CONTROLS PROTOTYPE for CALTECH and MIT. Both will be made by Caltech Machine shop. Piece parts being made at CALTECH now for the upper structure. Lower structure will be in the CALTECH Machine shop by the end of the month. RESONANCE TESTS at STANFORD - Stanford transfer function tests will be done with the Seismic technology demonstrator. LIGO-G050069-00-D

History: Other Examples LIGO-G050069-00-D

LIGO-G050069-00-D

GOAL: - 100 Hz 15% contingency LOWER STRUCTURE - JAN # of nodes 127,000 # of elements 66250 Fixed Support (for comparison only!) 1 st mode 146 Hz Transverse Mass 44 kg LIGO-G050069-00-D NOTE: - Comparative analysis done in ALGOR! 2nd mode 157 Hz Longitudinal

GOAL: - 100 Hz 15% contingency OVERALL STRUCTURE - JAN Mass 121 kg f1 99 Hz f2 111 Hz f3 177 Hz # of nodes 124,000 # of elements 62,021 Clamped at 14 fixed points LIGO-G050069-00-D

GOAL: - 100 Hz 15% contingency OVERALL STRUCTURE - FEB Latest Model Mass 133 kg Nodes 115,000 Elements 57,000 1st Mode 85 Hz (long.) 2nd Mode 94 Hz (trans.) 3rd Mode 144 Hz (tors.) LIGO-G050069-00-D