Maximum flexural stress sustained
by the test specimen (see Note 11) during a bending test.
It is calculated according to Eq 3 or Eq 4. Some materials that
do not break at strains of up to 5 % may give a load deflection
curve that shows a point at which the load does not increase
with an increase in strain, that is, a yield point (Fig. 1, Curve
B), Y. The flexural strength may be calculated for these
materials by letting P (in Eq 3 or Eq 4) equal this point, Y.