**6.2 Using the ABAQUS Combinend Hardening Model**

The cyclic deformation behaviour is described by the ABAQUS® *Combined Hardening Model* dependent on temperature and ageing. The corresponding variables are the temperaturecorrected time and the current temperature. The necessary parameters can be correlated with the *Rp0,2* yield limit from the Shercliff-Ashby model (Shercliff & Ashby, 1990). For the calculation of different states of ageing a user subroutine has been developed. On the one hand it allows for an accumulation of the temperature-corrected time on the basis of the temperature-time curve for separate calculation steps, and on the other hand it is possible to calculate directly the state of ageing for a certain ageing time according to the local maximum temperature.

The calculated hystereses and stress-time curves conform very well to the measured experimental data (fig. 8). Under TMF load both the asymmetry of the stress-strain hystereses and the stress relaxation in the dwell time region are expressed correctly.

**Mechanical strain [%]**

Fig. 8. Comparison of calculated and measured hystereses
