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A method to measure bridging stress by using bending test of a deepnotchedspecimen is developed in this paper. To obtain the bridging stress from theintegral equation which relates the bridging stress to the load, a numerical inverseanalysis method is also developed. By using the present method the authors evaluatedthe grain-bridging stresses of polycrystalline alumina ceramics with the mean grain sizeof 3 μm an 11 μm. The obtained results can be summarized as follows: (1) the meangrain size had no effect on the maximum bridging stress for alumina, (2) the correlationwas not observed between the maximum bridging stress and the bending strength foralumina ceramics.