Macroscopic and Microscopic Residual Stresses in Ceramics Due to Contact Loading
The paper deals with microplastic deformation and macroscopic residual stresses in silicon nitride ceramics due to contact loading and their effect on the near-surface strength. Depth-resolving X-ray residual stress measurements on shot peened samples detect high microplastic deformation and macroscopic compressive residual stresses up to 1.3 GPa at the surface decreasing to zero within 10 pm. These high compressive stresses enhance the load bearing capacity in the ball-on plate test up to 50 % compared to polished samples.
Characterisation and assessment of machined ceramic surfaces
L'article compile les caracteristiques essentielles des zones superficielles de ceramiques usinees, des schemas etablis et des methodes modernes d'investigation, et donne quelques exemples pour une evaluation pertinente pour l'emploi des surfaces modifiees par un usinage. Une attention particuliere a ete apportee aux methodes de diffraction des rayons X pour la caracterisation et aux methodes de la mecanique de la rupture pour une evaluation quantitative des surfaces usinees. Les exemples typiques concernent l'usinage par abrasion du carbure de silicium, du nitrure de silicium et de l'alumine et le comportement en service d'echantillons usines sollicites en fatigue par flexion et traction.
Influence of Texture ona(sin2ψ) Curves Obtained From a Cold Rolled Nickel Sheet using Synchrotron Radiation
The Two-Axis Diffractometer at HASYLAB was used to measure a(sin2ψ) curves 
by reflecting synchrotron radiation from five different lattice planes of a cold rolled 
nickel sheet. We are especially interested in the complex surface state of the 
specimen and investigated the sample as delivered without further polishing and 
etching. Strongly non-linear a(sin2ψ) curves were observed. Most of them vary in a 
non-linear way if external uniaxial stress is applied. In this paper we study the 
influence of texture using formalism based on the ODF, and evaluated for the Reuss 
and the Voigt cases, respectively. Texture alone, however, is not sufficient to explain 
the whole variety of the observed effects.