Effect of Specimen Geometry on Bending Strength of Ceramic/Metal Joints

The effect of specimen geometry on the bending strength of β-Si3N4/S45C joints with copper interlayer was evaluated by the method of JIS R 1624-1995. The validity of the method was confirmed. Average bending strength of circular-section specimens was higher than that of rectangular-section spceimens. Average bending strength of one-interface specimens was higher than that of two-interface specimens. Crack initiation stress (σi) was successfully detected by the acoustic emission (AE) method and found to be approximately 60∼80% of the bending strength. The residual stresses near the interface at the ceramic side were measured before the bending test by the X-ray diffraction method. The bending strength and the crack initiation stress were found to decrease with the increase of residual stresses.