The bending strength,
[MPa], is the most important parameter for estimating the
strength of components and for dimensioning them. Tables of
materials properties contain values obtained from either 3-point
or 4-point tests on special bending test bars. The value obtained
from the 3-point bending test is around 30% higher than that
from the 4-point test. In Germany it is usual
to quote figures based on the 4-point procedure.
Comparing the data is often made more difficult by the absence
of information about the method used for the measurement.
The values for a component's bending strength are affected
by the size, shape, surface ("as fired", ground
etc.), and, in some cases, by inhomogeneities in the microstructure
resulting from the manufacturing process.
Test procedures for determining the bending strength are defined
in DIN EN 843-1, DIN EN 820-1 and DIN EN 60 672-2.
Figure 83: Bending strength of selected materials
Technical ceramics are distinguished by
their very good high-temperature strength, with maximum working
temperatures that even exceed those of metallic superalloys.
Ceramic materials are thus ideal for applications in high-temperature
processes (see Figure 84).
Figure 84: Effect of temperature on bending