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Development of Safe Cooling Schedules for Structural Clay Products
Author(s) -
LACHMAN IRWIN M.,
EVERHART J. O.
Publication year - 1956
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1956.tb15595.x
Subject(s) - thermal expansion , thermal diffusivity , materials science , elasticity (physics) , quartz , dimensionless quantity , thermodynamics , young's modulus , thermal , modulus , composite material , bulk modulus , physics
A method is described whereby safe cooling schedules for structural clay products are developed, based on a criterion for thermal failure. Resistance to thermal failure may be indicated by the following equation: Resistance = MR a/Ea, where MR is the modulus of rupture, E is the modulus of elasticity, a is the thermal diffusivity, and a is the coefficient of linear thermal contraction. The modulus of rupture, modulus of elasticity, linear thermal contraction, and relative thermal diffusivity of three commercial bodies were measured in the temperature range 1600°F. to room temperature. Using the experimental values, relative cooling schedules are developed in terms of ware temperature versus dimensionless time, the total time for cooling being a function of size and shape. The order of importance of the physical properties is discussed with respect to cooling schedules and it is concluded that the coefficient of linear thermal contraction has the greatest effect. The mechanisms acting in clay bodies during cooling are discussed and the idea of quartz separation is presented. The hysteresis of the modulus of elasticity and coefficient of thermal expansion while heating and cooling is correlated with quartz separation and the literature is cited to support the idea. Some tests are described to show that rebonding of the quartz occurs on reheating to sufficiently high temperatures.