RESIDUAL STRAINS IN AN AL2O3-NI JOINT BONDED WITH A COMPOSITE INTERLAYER - EXPERIMENTAL MEASUREMENTS AND FEM ANALYSES

A cylindrical Al2O3-Ni joint bonded with a 4.0 mm thick composite inte rlayer of 40 vol% Al2O3-60 vol% Ni was fabricated by powder processing , and the residual strains in the specimen were studied experimentally using neutron diffraction, X-ray diffraction, and optical fluorescenc e spectroscopy. Experimental measurements were compared with finite el ement modeling results obtained using a variety of different constitut ive assumptions. The predicted residual strain distribution within the Al2O3 along the center of the specimen was in reasonable agreement wi th neutron diffraction measurements, although the magnitude of the err or in the experimental measurements did not allow a distinction to be made between the various modeling assumptions examined. In contrast, t he predicted peak strains within the Al2O3 along the specimen surface were significantly higher than those measured by X-ray diffraction or optical fluorescence spectroscopy, suggesting that strain relief occur red near the free edge during cooling. The mechanism of strain relief is believed to involve damage accumulation within the composite interl ayer that was not accounted for in the constitutive models used.