Breviary Technical Ceramics



 Creep properties

Plastic deformation of metallic materials under static loads is observed in long term experiments. Creep phenomena are amplified at higher temperatures and limit the application possibilities of metallic materials. Generally speaking, the tendency of ceramic materials to creep at temperatures below 1,000°C is very low. However, in contrast to metallic materials, creep extensions of only a few per cent can lead to failure of the material. As opposed to slow crack growth, in which a single crack propagates, creep damage is understood as the development of creep porosity and microcracks. This causes a relatively homogeneous distribution of damage through the entire volume of the material under stress. As a result, the physical properties of the material are changed.

The creep behaviour in ceramic materials is influenced not only by the stress but also the chemical bonding and microstructure characteristics (grain size, grain shape, porosity, grain boundary phases).

Test procedures for determining the parameters of creep deformation in flexure at high temperatures are specified in DIN ENV 820-4 and EN 820-2.


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