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FP5

BIOGRAD Report Summary

Project ID: G5RD-CT-2000-00354
Funded under: FP5-GROWTH
Country: Czech Republic

Neutron diffraction characterization of residual stresses in graded AL2O3-ZrO2 ceramics

The main task of the NPI participant in the BIOGRAD project was the neutron diffraction characterization of graded Al2O3/Y-ZrO2 ceramics. Neutron diffraction methods of determination of internal strains and stresses in structural materials have found a lot of applications in material sciences and engineering. However, application of the convention neutron diffraction method has been found rather difficult in the studied multiphase system with a gradient of phase composition. The diffraction methods use the crystal lattice as a built-in strain gauge and the corresponding information on stress state is then received from each phase separately. From technological point of view, the most important characteristics of graded ceramics are the distribution of the macroscopic residual stresses. These stresses result mainly from the phase specific stresses after cooling from sintering temperature and could be varied by an appropriate selection of the phase gradient. The used diffraction method provides information on lattice strains, which are detected in each constituent phase individually. The experimentally observed value of lattice strains reflects superposition of both phase specific strains and macroscopic residual strains. Within the BIOGRAD project, the new concept of determination both stress/strain components, i.e. the macroscopic residual stress and the phase specific stresses was developed.

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Petr LUKAS, (vice director)
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