Subproject C5 Crack growth

In sub-project C5, a quasi-static, multi-scale method for the simulation of cracks based on the XFEM has been developed that can take into account thermal loadings, heat conduction, non-local damage, as well as possible crack face contact to simulate regenerated parts under realistic circumstances. However, the quasi static model can only estimate the remaining life time due to an inaccurate reflection of the complex dynamic interactions. It is therefore necessary to extend the model to include inertia terms. To simulate dynamic crack growths for a large number of load cycles efficiently and accurately within reasonable computing times, the multi-timescale method WATMUS will be applied.

The existing XFEM implementation is extented by inertia terms at one scale. After that, the equation of motion is cupled to transient heat conduction as well as to non-local damage. The coupled equations will be solved explicitly and simultaneously for each time step. Eventually, this implementation will be coupled to the multiscale projection method.

The temperature distribution on the surface of turbine blades/blisks from CFD simulations of sub-project C3 can be applied as boundary conditions. The maximum vibration amplitude and material parameters needed for the XFEM-analysis are taken from sub-project C3.

The transient simulation of the multiscale crack propagation under dynamic excitation allows for a mor precise prediction of the remaining life time of each specific engineering part, without the necessity of empirically gathered data. Thus, within the CRC a more precise evaluation of the regeneration paths is possible.

The developed methods can be readily employed for other capital goods in the industry, such as the thermal-mechanically highly loaded drives of diesel locomotive.