1. Instrumentation of Breaking Glass Strobe 6: Friday 10am–1pm strobe6@mit.edu Adam Seering aseering@mit.edu Aubrey Tatarowicz altat@mit.edu Daniel Hernandez djh@mit.edu John Hawkinson jhawk@mit.edu

2. 2 How does glass break? — What ways can we instrument the cracking process? Concept - What we did - Results - Feasible? - Timeline

3. 3 Making it break!  We tried several ways: Heat on glass + cold water (for thermal shock) Impact from a falling weight BB gun  What can we measure and quantify? Concept - What we did - Results - Feasible? - Timeline

4. 4 What we want to measure (goals)  Is there a consistent shape to the breaking?  What is the rate and pattern of deformation and breakage?  How does glass breaking process depend on glass thickness?  Comparison of different measurement techniques Schlieren, electrically conductive tape, video  Effects of different-shaped impact objects (screwdriver, BB, etc.)  What are the effects of temperature? Concept - What we did - Results - Feasible? - Timeline

5. 5 Investigation of breaking by thermal shock  1mm thick microscope slides, clamped to lab stand  ~200°C soldering iron: did not break on instant contact Nor did glass break on sustained contact  380°C from heat gun Still glass slide does not break Concept - What we did - Results - Feasible? - Timeline

6. 6 Thermal Shock Works! 1.380°C from heat gun 2.Release drop of water →Whether the slide breaks depends on height of water release Concept - What we did - Results - Feasible? - Timeline

7. 7 Lighting

8. 8 Investigation of glass breaking by impact  Thicker sheets of glass — 3 / 32 " (2.4 mm)  Cut sheets to ~2"x8"  Taped across apple boxes  Dropped mass (screwdriver) from different heights Concept - What we did - Results - Feasible? - Timeline

9. 9 Results We can measure crack motion in time Concept - What we did - Results - Feasible? - Timeline 13 μs per step

10. 10 Results We observe flexing of glass, but want a better visuals and instrumentation. Ideas: try projecting a grid onto glass, or view glass edge-on Concept - What we did - Results - Feasible? - Timeline

11. 11 Lighting to get good results  Back lighting and side lighting work well in order to see cracking, these were used in the images in the previous slides  Top lighting produces a lot of glare

12. 12 YES! It is feasible  From the trials with slides We can measure the speed of the crack motion We can break with force and/or thermal shock However, it might be hard to see deformation on slide since they are so small  From the thick sheets, We can see glass flexing upon impact of blunt object The shattering is more defined — will probably yield better results than the slides Concept - What we did - Results - Feasible, YES! - Timeline

13. 13 Cost is cheap!  One 8"x10" sheet of glass costs $2 Cut into five 2“ inch slices → $0.40 per slice  Box of slides costs $8 (72 slides) $0.11 per slide Concept - What we did - Results - Feasible, YES! - Timeline

14. 14 Future direction  Thicker sheets are more exciting than small slides: need to reproduce thermal shock using sheets.  We want to try different lighting techniques and camera angles since these factors will be key in being able to extract useful data. Concept - What we did - Results - Feasible, YES! - Timeline

15. 15 Timeline Week 1 (of Nov. 3) BB gun, grid reflection, consistency between slides/sheets, pendulum break of slides; heat on the sheets (hotter than heat gun, flame) Rotate the glass...break on-end. Week 2 (of Nov. 10) Try Schlieren imaging to capture heat distribution and flexing when breaking Week 3 (of Nov. 17) Lots of trials of what we found works well. Analyze data. Week 4 (of Nov. 24) Get beautiful images, still images (this may be the same thing). Analyze more data. Week 5 (of Dec. 8) Write-up do whatever we need to finish Concept - What we did - Results - Feasible, YES! - Timeline

16. Instrumentation of Breaking Glass Strobe 6: Friday 10am–1pm strobe6@mit.edu Adam Seering aseering@mit.edu Aubrey Tatarowicz altat@mit.edu Daniel Hernandez djh@mit.edu John Hawkinson jhawk@mit.edu