Procedures for handling computationally heavy cyclic load cases with application to a disc alloy material

The computational efficiency in analysing cyclically loaded structures is a highly prioritised issue for the gas turbine industry, as a cycle-by-cycle simulation of e.g. a turbine disc is far too time consuming. Hence, in this paper, the efficiency of two different procedures to handle computational expansive load cases, a numerical extrapolation and a parameter modification procedure, are evaluated and compared to a cycle-by-cycle simulation. For this, a local implementation approach was adopted, where a user-defined material subroutine is used for the cycle jumping procedures with good results. This in contrast to a global approach where the finite element simulation is restarted and mapping of the solution is performed at each cycle jump. From the comparison, it can be observed that the discrete parameter modification procedure is by margin the fastest one, but the accuracy depends on the material parameter optimisation routine. The extrapolation procedure can incorporate stability and/or termination criteria.