WP1 Project management & Dissemination and exploitation set up necessary processes for the project management, dissemination, communication and exploitation. The website and social media channels were launched, and templates produced. The project has resulted in 9 peer-review journal papers, 2 conference papers, 22 conference presentations, 3 posters and 20 other events including TMF courses. One of the main achievements was co-organisation of an international conference, TMF Workshop 2019, Berlin, Germany. The consortium also facilitated a panel discussion for sharing know-how, and further engagement and collaboration towards standardisation of TMF CG testing. To promote a wider uptake of the results, DevTMF organised a symposium under the EUROMAT 2019 conference in Stockholm.
WP2 Experimental activities including characterisation work performed extensive TMF testing and characterisation of two alloys to determine effect of different loading variables and component flight-like complex cycles. One of the main achievements under WP2 is the TMF CG round robin testing forming the basis for a local Code of Practice and standardisation. Precise and stable non-invasive temperature measurements were developed using infrared thermography (IRT). This approach was also used to measure and understand crack tip heating in induction coil as well as innovative measurements of TMF CG rates, Figure 1. The method enables measurement of crack length and removes complications with PD probes and coil interferences. Detailed investigations of other temperature measurement methods were also performed.
c.
Various characterisation techniques were used, e.g. SEM, EBSD, TEM, FIB-SEM, DIC, nanoindentation, to understand material behaviour, Figure 2.
WP3 Modelling activities including validation work developed a viscoelastic-viscoplastic constitutive material model capturing cyclic plasticity and viscous flow, Figure 3. A subroutine for the material model was written for integration in commercial FEA codes. Crack initiation life was estimated using a damage accumulation model based on the memory surface concept of Jiang. To account for elastic damage, a simple critical plane search algorithm, calculating stress tensors experienced by a particular plane in the material affecting fatigue life, was considered. To reduce CPU time and increase efficiency, additional subroutines for cycle jumping procedures were developed.
For simulation and prediction of TMF CG, a model accounting for fatigue, creep crack growth and a participation size effects was developed, Figure 4.
In addition, generalised crack tip modelling scripts to correlate plastic strain with degradation in Young’s modulus (a function of accumulated plastic strain) and SIF were formulated, Figure 5.
The models and methods were validated and evaluated for various loading conditions showing good agreement with the experimental data in most cases.
