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Tempered or toughened glass is a type of safety glass processed by controlled thermal or chemical treatments to increase its strength compared with normal glass. Tempering puts the outer surfaces into compression and the interior into tension .
Toughened glass is processed by controlled thermal or chemical treatments to increase its strength compared with normal glass. [6] Tempering, by design, creates balanced internal stresses which causes the glass sheet, when broken, to crumble into small granular chunks of similar size and shape instead of splintering into random, jagged shards.
Also unlike toughened glass, chemically strengthened glass may be cut after strengthening, but loses its added strength within approximately 20 mm of the cut. Similarly, when the surface of chemically strengthened glass is deeply scratched, this area loses its additional strength. Another negative of chemically strengthened glass is the added cost.
Float glass is a sheet of glass made by floating molten glass on a bed of molten metal of a low melting point, typically tin, [1] although lead was used for the process in the past. [2] This method gives the sheet uniform thickness and a very flat surface. [ 3 ]
In automobiles, the laminated glass panel is around 6.5 mm (0.26 inches) thick, in comparison to airplane glass being three times as thick. [21] In airliners on the front and side cockpit windows, there is often three plies of 4 mm toughened glass with 2.6 mm thick PVB between them.
Glass fibers have a much higher tensile strength than regular glass (200-500 times stronger than regular glass). [7] This is due to the reduction of flaws in glass fibers [8] and the small cross sectional area of glass fibers, constraining maximum defect size.
In toughened glass, compressive stresses are induced on the surface of the glass, balanced by tensile stresses in the body of the glass. Due to the residual compressive stress on the surface, toughened glass is more resistant to cracks, but shatter into small shards when the outer surface is broken.
In a monolithic Pd–Ag–P–Si–Ge glass alloy, the properties of high bulk modulus and low shear modulus lead to proliferation of shear bands. These bands are self constrained and the toughness is improved. [3] Metals can be toughened by improvement of processing. With a high affinity for oxygen, titanium alloy can absorb oxygen easily. [4]