Measurement of Residual Stresses in Oxide–ZrO₂ Three‐Layer Composites

Al₂O₃–ZrO₂ and MgO–ZrO₂ layered composites were fabricated in such a way that the outer layers of bar‐shaped specimens consisted of the oxide (Al₂O₃ or MgO) and unstabilized ZrO₂, while the bulk consisted of the oxide and partially stabilized ZrO₂. During cool‐down from the sintering or the annealing temperature, the outer layers expanded because of the tetragonal → monoclinic transition in ZrO₂, thereby creating compressive stresses in the outer layers and tensile stresses in the bulk. Residual stresses were determined using a strain gage technique in which a strain gage was mounted on one face while the opposing face was incrementally ground off. Measurement of the strain as a function of thickness permitted the evaluation of residual stresses using pertinent equations from simple beam theory.