Stresses in glasses Flashcards

1
Q

What happens to a glass bottle formed in a steel water-cooled mold? The interior and exterior?

A

~ exterior: cools quickly to liquid like LOW density, puts TENSILE stress on interior

~ interior: insulated by exterior, cools slowly and condenses to HIGH density, puts COMPRESSIVE stress on exterior

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2
Q

How do we prevent these bottles from spontaneously bursting on store shelves?

A

~ annealing: reheating bottle to annealing point and holding for short time

~ enough thermal energy is provided for RELAXATION of atomic strains, but viscosity is high enough so part doesn’t slump

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3
Q

What are polariscopes used for? How do they work?

A

~ checking for residual stresses in a glass part

~ unstrained glass = isotropic, appears dark

~ strained glass = birefringent, appear as colors

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