Instrumentation of Breaking Glass

1. Instrumentation of Breaking Glass Strobe 6: Friday 10am–1pmstrobe6@mit.edu Adam Seering aseering@mit.edu Aubrey Tatarowicz altat@mit.edu Daniel Hernandez djh@mit.edu John Hawkinson jhawk@mit.edu

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

3. Making it break! Concept - What we did - Results - Feasible? - Timeline • 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?

4. What we want to measure (goals) Concept - What we did - Results - Feasible? - Timeline • 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 • Electrically conductive paint versus video • Look at heat distribution w/ Schlieren imaging • Effects of different-shaped impact objects (screwdriver, BB, etc.) • What are the effects of temperature?

5. Setup photo Concept - What we did - Results - Feasible? - Timeline

6. Investigation of breaking by thermal shock Concept - What we did - Results - Feasible? - Timeline • 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

7. Thermal Shock Works! Concept - What we did - Results - Feasible? - Timeline • 380°C from heat gun • Release drop of water → Whether the slide breaks depends on height of water release

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

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

10. ResultsWe 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 47,000fps; 21μs Frame 2 Frame 1 21μs

11. Lighting to get good results Concept - What we did - Results - Feasible? - Timeline • Top lighting produces a lot of glare • Back lighting and side lighting work well in order to see cracking, these were used in the images in the previous slides

12. YES! It is feasible Concept - What we did - Results - Feasible, YES! - Timeline • 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

13. Cost is cheap! Concept - What we did - Results - Feasible, YES! - Timeline • 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

14. Future direction Concept - What we did - Results - Feasible, YES! - Timeline • 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.

15. Timeline Concept - What we did - Results - Feasible, YES! - Timeline

16. Instrumentation of Breaking Glass Strobe 6: Friday 10am–1pmstrobe6@mit.edu Adam Seering aseering@mit.edu Aubrey Tatarowicz altat@mit.edu Daniel Hernandez djh@mit.edu John Hawkinson jhawk@mit.edu