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E. C. WIGGLESWORTH; The Effect of Thermal Toughening on the Impact Resistance of Simulated Safety Lenses. Invest. Ophthalmol. Vis. Sci. 1971;10(12):992-999.
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© ARVO (1962-2015); The Authors (2016-present)
Flat glass specimens, simidating eye protector lenses, were generated in seven thicknesses between 1.3 and 4.0 mm. Half the specimens, randomly selected, were heat treated and all were then dynamically tested to destruction. The results show that the effect of the heat treatment was to increase the impact resistance, measured in terms of fracture velocity. For all thicknesses, the approximate relationship was found to be V2/V1 = √2, where V1 = fracture velocity of the untoughened specimens and V2 = fracture velocity of the toughened specimens. The same relationship was found to hold for a group of +1.75 diopter spherical meniscus lenses of center thickness 2.0 mm. and edge thickness 1.0 mm. and of base curve 6.00 diopter, similarly treated. The relationship was independent of missile diameter in drop-tower tests (simidating blunt trauma from large missiles) and in ballistic experiments (simulating penetrating injuries from small missiles).
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