Procedures
The specimens were tested in three-point (16 mm span between the bearing rollers) or four-point flexure (20–40 mm spans between the bearing rollers) on a home-made Ceramtest block, mounted on a universal testing machine and fitted with a hard load cell, a system for precision displacement of a loading rod, and loading supports.
The latter are equipped with an attachment for the rotation of the bearing rollers during specimen loading.
Three-point flexure required the precise alignment of a specimen on the bearing rollers, with the axis of the central bearing roller and the radius of the Vnotch root being in the same plane as the applied load.
In high-temperature tests, we used a loading block which is similar to that used in room temperature tests.