1. Some recent work on blade performance Caroline Cantley, Justin Greenhalgh, Mike Plissi, Norna Robertson, Calum Torrie, Ian Wilmut LSC, March 2004 LIGO-G040058-00-K

2. Contents • Theoretical work • “Blade committee” • Blade design equations • FEA on transmissibility • Practical work • Test blades of topmost ITM type • Blade test facility

3. Blade committee - 1 • Norna Robertson, Calum Torrie, Mike Plissi, Justin Greenhalgh, Caroline Cantley • Meet by telecon • Aim to pin down blade design issues: • How to predict blade performance (alpha and E) • Manufacturing processes • Selection of supplier • Heat treatment • Stress-relieving under load (?) • Load & factor of safety • Avoid “noisy” creep in use (also for clamps)

4. Blade committee - 2 • Conclusions so far: • Young’s Modulus varies between batches of maraging steel, so we should use a common manufacturer or maybe even a single order for the project. • Plan to make two large blades plus test samples at the same time, then measure E of samples and blade performance • Results from Virgo suggest that the heat treatment regime we have used may not be optimal, need to investigate further • Plan some tests at RAL using AE to look for noisy creep and, if found, verify that gentle heating under load removes it

5. Blade design equations • Rerun through blade design equations, simply restating results of others (T030285) • Non-linear FEA to look at initial deflection of blades • Very simple work at RAL, preliminary to transmissibility (T040024) • Some work to look at the relationship between FEA predictions and those of the blade design equations • Recheck of earlier results – alpha and Young’s modulus • Suggests that use of the geometric value of alpha plus measured value of E gives good fit to results.

6. Blade Equations

7. FEA on blade transmissibility • To check that the transmissibility peaks associated with the internal modes of the three sets of blades would not interfere with each other • To assess the impact of wire clamp mass

8. Check normal modes FE vs measurements

9. Transmissibility • 0-1000 Hz • NB 1 Hz steps • Misses first bounce mode

10. Model with wire and wire clamp

11. Results combined for three blades

12. Future work on transmissibility • Future work • Complete analysis of current blade designs • Compare with experimental results (eg Torrie thesis) • Especially, verify Q of blades

13. Blade test facility • Talk by Ian Wilmut

14. Blade test facility • What is it? • A simple way of experimenting with large blades, blade clamps, wire clamps etc… • The BTF resembles the upper-stage of a quad pendulum • Why are we building it? • To tie the blade theory up to real life • To allow blade sub systems to be iterated • Work on different designs of blade clamps • Work on different wire clamp designs • Work on different blade geometries • Provide test bed for eddy-current damping of blades • Allow different blade loading techniques to be tried

15. Blade test facility

16. Blade Straightening • Previous blades have been straightened by loading with weights, a ETM would require 62kg per top stage spring. • Proposed alternative uses a roller to straighten the blades.

17. Blade clamps • 2 designs of the blade clamp • Library of clamps in a very similar arrangement as the mode cleaner. • Rotating design intended to provide blade tip height adjustments.

18. Wire Clamps • Initial wire clamp design to be similar to mode cleaner. • Rendering shows basic wire clamp • It is intended that we iterate on:- • Clamp grove design • Wire flexure point design • Definition of clean break-off

19. Plan of work with BTF • Flatten blades with blade straightening carriage. • Define alpha for quad upper blades using Young’s modulus measured from 10 samples of the same material. • 5 samples near surface • 5 samples near core, of ¼” material • Test idea for rotational adjuster • Iterate on wire clamp design details • Can be for other tests eg noisy creep