WINDOW TESTING NEWS

1. WINDOW TESTING NEWS

2. WINDOW TESTING NEWS • Tested window 3 • used “perfected” system • broke at predicted pressure • FEA successes/ FEA problems • Plans • new discovery • use photogrammetry to measure thickness

3. Improvements made Increased information in central regions Increased stability of system • Projector • Camera (tripod, remote shutter) • Pressurization system

4. Payoff from improvements Xrms, Yrms, Zrms ~ 5um

5. WINDOW TESTING NEWS • Tested window 3 • used “perfected” system • broke at predicted pressure • FEA successes/ FEA problems • Plans • new discovery • use photogrammetry to measure thickness

6. Burst pressure

7. Equipment protection

8. Video camera Video camera

9. Information from video 1/30 second - a few drops on shield + 1/30 second - hear & see tear ……..cannot see where tear began

10. WINDOW TESTING NEWS • Tested window 3 • used “perfected” system • broke at predicted pressure • FEA successes/ FEA problems • Plans • new discovery • use photogrammetry to measure thickness

11. FEA success Window 1

12. FEA problems • Window 1 has the correct geometry in the FEA model. • FEA deflection = measured deflection • Window 2 & 3 incorrect geometry input to FEA • FEA deflection > measured deflections • Window is thicker than input geometry indicated, hence under-estimated true stiffness

13. WINDOW TESTING NEWS • Tested window 3 • used “perfected” system • broke at predicted pressure • FEA successes/ FEA problems • Plans • new discovery • use photogrammetry to measure thickness

14. Newest discovery Periodic variation observed in deflection as f(azimuth) may be an indication of harmonic variations in the circumferential direction.

15. Newest discovery • At the crown end where the crown radius is forced to join the knuckle, known as the junction of discontinuity, compressive stress will develop in order that the two new radii can join up. • To allow the dissipation of this compressive stress, the knuckle will develop a number of this wrinkles, or ripples, around its circumference. The number of ripples depends of the magnitude of the compressive stress. 4 is the starting point, hence the term harmonic 4. • As the rest of the crown is relatively thin, the presence of these ripples, normally in micron level, suddenly become significant. Because of this, it allows these ripples to extend from the knuckle region to the rest of the crown towards its center. • As the pressure builds up, the crown stretches out more, like an inflated balloon, thereby counter balancing the effect of these ripples, similar to the straightening of a fold line. This is why we see less and less of the harmonic effect at the crown center as the pressure builds up.

16. Explanation of compressive forces in torispherical endcap R >> r R r Shape of the original pressure envelope Tensile stresses Discontinuity between the 2 radii which causes compressive stresses Deformed shape of the different pressure envelope under a uniform pressure

17. Newest discovery • Use a 3-D model with fine enough mesh to cover the knuckle region so that it can compute the expected compressive stress (will take 3-5 days to run FEA) • This static harmonic variation can be represented by a Fourier series if one can work out the magnitude of the coefficients a0, a1, a2….an and b0, b1, b2, ….bn etc.

18. WINDOW TESTING NEWS • Tested window 3 • used “perfected” system • broke at predicted pressure • FEA successes/ FEA problems • Plans • new discovery • use photogrammetry to measure thickness

19. Window thickness from photogrammetry • Plan to measure window thickness using photogrammetry (currently use CMM) • Procedure: perform photogrammetric measurements on both sides of the window.

20. Photogrammetry setup for thickness measurement

21. Window thickness from photogrammetry front back

22. Window thickness from phothogrammetry front/back

23. Thickness calculation • Use VANGO to create a surface model • VANGO is CADD software for land development civil engr and surveying • VANGO evolved from Van DellCO GO • CO GO = coordinate geometry

24. Check Met-L-Chek • Met-L-Chek : Fluorescent and Visible Dye Penetrant Inspection Materials • Met-L-Chek= beads in matrix of isopropyl alcohol • Recently learned beads can be as large as 15um (previously thought beads were sub-micron) • Measure effect of thickness of Met-L-Chek