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

How does glass break?— What ways can we instrument the cracking process?

Concept - What we did - Results - Feasible? - Timeline

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

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

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?

Concept - What we did - Results - Feasible? - Timeline

5

Setup photo

Concept - What we did - Results - Feasible? - Timeline

6

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

7

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

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

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Results We can measure crack motion in time

Concept - What we did - Results - Feasible? - Timeline

13 μs per step

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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

21μs

47,000fps; 21μs

Frame 1 Frame 2

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Lighting to get good results 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

Concept - What we did - Results - Feasible? - Timeline

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

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

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

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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

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