The high quality required for special components of structural ceramics can only be achieved by an additional fine-machining. Since processes like lapping or grinding strongly influence the service behaviour of the components and in addition cause a considerable part of the manufacturing costs there is a need for parameter studies in order to optimize the resulting quality and reduce the costs of the machining process.

Therefore, the strength-controlling surface effects have been investigated using a newly developed method for the determination of micro-strains and residual stresses by x-ray diffraction techniques. The resulting information on the defect situation in the surface layer can be modeled by assuming hypothetical cracks. When the additional information on the distribution of the residual stresses caused by machining and the strength properties obtained from bending tests are taken, as a consequence, the effects of damage processes and residual stresses on the strength of ceramics can be quantified by the methods of fracture mechanics.

Typical case studies will be discussed in which different grinding and lapping procedures are applied to specimens of silicon nitride and alumina.