The process of joining ceramics to metals is an important technique for the practical application of ceramics. Among the most available bonding technique is brazing. Metal/ceramic bonds subject to residual stress caused by thermal expansion misfit have been investigated in an $Al_2O_3$/Ag-Cu-Ti/Carbon steel system. The residual stresses cause cracking of either the $Al_2O_3$ or the reaction layer, dependent on the magnitude and the direction of σ I. The observed locations, orientations, and trajectories of the cracks have been rationalized on the basis of residual stress fields. Considering the industrial use of the bonding process, is necessary to establish nondestructive testing methods for verification of quality. In this study acoustic emission method is introduced to metal/ceramic joining.