Practical assessment of long-term behaviour

The theory relating stress, strain, time and temperature of viscoelastic materials is complex. For many practical purposes it is often better to use an ad hoc system known as the pseudo-elastic design approach. This approach uses classical elastic analysis but employs time- and temperature-dependent data obtained from creep curves and their derivatives. In outline the procedure consists of the following steps  

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The above considerations imply that the short-term tests can provide only very approximate data on the behaviour of a refractory at high temperatures. Much more precise data are provided by long-term measurements under various loads and at various temperatures, but these are not suitable for rapid practical assessment either in manufacture or by the user. This is why short-term tests have survived in technical practice. 

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