Instrumentation of Breaking Glass Strobe 6 Friday 10

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

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

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

Concept - What we did - Results - Feasible? - Timeline What we want to measure (goals) o o 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 n o o Schlieren, electrically conductive tape, video Effects of different-shaped impact objects (screwdriver, BB, etc. ) What are the effects of temperature? 4

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

Concept - What we did - Results - Feasible? - Timeline Thermal Shock Works! 1. 2. 380°C from heat gun Release drop of water → Whether the slide breaks depends on height of water release 6

Lighting 7

Concept - What we did - Results - Feasible? - Timeline Investigation of glass breaking by impact o o Thicker sheets of glass — 3/32" (2. 4 mm) Cut sheets to ~2"x 8" Taped across apple boxes Dropped mass (screwdriver) from different heights 8

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

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

Lighting to get good results o o 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 11

Concept - What we did - Results - Feasible, YES! - Timeline YES! It is feasible o From the trials with slides n n n o 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, n n We can see glass flexing upon impact of blunt object The shattering is more defined — will probably yield better results than the slides 12

Concept - What we did - Results - Feasible, YES! - Timeline Cost is cheap! o One 8"x 10" sheet of glass costs $2 n o Cut into five 2“ inch slices → $0. 40 per slice Box of slides costs $8 (72 slides) n $0. 11 per slide 13

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

Concept - What we did - Results - Feasible, YES! - 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 Lots of trials of what we found works well. Analyze data. (of Nov. 17) Week 4 (of Nov. 24) Get beautiful images, still images (this may be the same thing). Analyze more data. Week 5 Write-up do whatever we need to finish (of Dec. 8) 15

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