METAL THICKNESS EFFECT ON THE CALIBRATION OF STRESS INTENSITY FACTORSFOR SI3N4 FE AND AL2O3/AU JOINTS/

Measurement of interface fracture toughness requires knowledge cf the appropriate K -calibration functions for the pertinent test geometries rind material combinations. The 4-point-bending geometry has been use d in this study to calibrate the stress intensity factors in order to measure fracture toughness of metal/nitride ceramic, Si3N4/Fe/Si3N4: a nd metal/oxide ceramic, Al2O3/Au/Al2O3 joints over the full range of m ode mixity. This Calibration was carried out via finite element analys is. Specific techniques were adopted to decouple the two modes of frac ture at the interface crack-tip. The K -calibration functions for the pertinent geometry are strongly dependent on the-metal interlayer thic kness, particularly for loading conditions close to the model I.. Expe rimental results are presented for the Si3N4/Fe/Si3N4 system. (C) 1998 Elsevier Science Ltd. All rights reserved.