Figs.10 presents the experimental comparisons of the measured
stress-strain hysteresis responses for the 1st cycle
between SSFS and MTP specimens for FV566 steel at 600 °C subjected to
saw-tooth loading. The accuracy of the 1st hysteresis
loop under high temperature LCF test is particularly important as it can
be used to determine the elastic and kinematic parameters, e.g.,E ,
,
,
,
for Chaboche unified visco-plastic model in this
paper1-3. As can be seen from Fig.10 (left), the
reversible hysteresis responses from MTP specimens using the determined
scaling factors show an excellent agreement comparing with the SSFS
testing results under the equivalent testing conditions, in particularly
for the MTP-3 with the weakest geometry constraint effect. In addition,
the hysteresis loops of MTP specimens exhibit obvious identical dynamic
strain hardening as SSFS testing. To enable a direct comparison of
temporal stress evolution behavior between SSFS and MTP specimens, the
stress data versus normalized time are plotted in Fig.10 (right), again,
showing a very good agreement. Maximum tensile and minimum compressive
stresses in the three MTP specimens are nearly identical to those from
the SSFS testing for the first cycle, especially for the MTP-3 specimen.