ruperts drop - Prince Ruperts Drop: Glass tempering 1....

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Prince Rupert’s Drop: Glass tempering 1. Introduction This lab will demonstrate properties of tempered glass versus annealed glass. The strength of a glass product can be enhanced by inducing a compressive stress near the surface of the material. This compressive stress is achieved by a process called thermal tempering. The process involves first raising the glass above the glass transition temperature (T g ) and then cooling the surface of the material at a higher rate than the interior. Because glass has a low thermal conductivity, the surface of the sample will cool much faster than the interior of the sample. This results in the surface becoming solid, yet the interior can still flow. When the interior finally cools, the reduction in volume causes a tensile stress in the interior and a compressive stress on the surface. The resultant material is tougher because surface cracks will be in compression, causing the crack to close, rather than in tension which would cause it to open. In addition to increased toughness, tempered glass also experiences significantly enhanced bifurcation during crack propagation. This results in very small particles rather than large shards, which provides an additional level of safety (small particles can cut you,
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ruperts drop - Prince Ruperts Drop: Glass tempering 1....

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