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 interlayer 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 fluorescence spectroscopy. Experimental measurements were compared with finite element modeling results obtained using a variety of different constitutive assumptions. The predicted residual strain distribution within the Al₂O₃ along the center of the specimen was in reasonable agreement with neutron diffraction measurements, although the magnitude of the error in the experimental measurements did not allow a distinction to be made between the various modeling assumptions examined. In contrast, the 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 occurred near the free edge during cooling. The mechanism of strain relief is believed to involve damage accumulation within the composite interlayer that was not accounted for in the constitutive models used.