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Thermal expansion mis-match. Poor fit between the glaze and the body's thermal expansion is the main cause of crazing and can be due to: Under-firing resulting in failure to develop sufficient body thermal expansion. Firing too quickly, resulting in failure to achieve sufficient heatwork. Low thermal expansion body. High thermal expansion glaze.
This may occur where the glass is partially shaded and partially heated from the sunlight. Tinted glass increases heating and thermal stress, while annealing reduces internal stress built into the glass during manufacturing. Thermal expansion creates internal pressure, or stress, where expanding warm material is restrained by cooler material.
Argon [57] [58] proposed an alternative crazing criterion based on a molecular theory for distortional plasticity, he described the process of crazing as a micromechanical problem of elastic-plastic expansion of initially stable micropores produced by a thermally activated mechanism under stress to form a craze nucleus. With his analysis of the ...
This weakens the edge, so less stress is required to cause the failure. The probability of this type of thermal fracture cannot be determined using thermal assessment processes. High energy: These are rare and require high levels of thermal stress. The probability of this type of thermal fracture can be determined using thermal assessment ...
Annealing is a process of slowly cooling hot glass objects after they have been formed, to relieve residual internal stresses introduced during manufacture. Especially for smaller, simpler objects, annealing may be incidental to the process of manufacture, but in larger or more complex products it commonly demands a special process of annealing in a temperature-controlled kiln known as a lehr. [1]
Thermal shock resistance measures can be used for material selection in applications subject to rapid temperature changes. The maximum temperature jump, , sustainable by a material can be defined for strength-controlled models by: [4] [3] = where is the failure stress (which can be yield or fracture stress), is the coefficient of thermal expansion, is the Young's modulus, and is a constant ...
Binding of the glass in the frame, causing stresses to develop as the glass expands and contracts due to thermal changes or deflects due to wind. Glass expands and contracts with changes in temperature and deflects due to wind, so almost all modern glass is set on resilient blocks at the bottom and with space for expansion at the sides and top.
Guitar slide made of borosilicate glass. Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10 −6 K −1 at 20 °C), making them more resistant to thermal shock than any other common glass.