Flexible Multibody modelling and simulation
A dynamic model of a reference three blades turbine will be developed by a flexible approach to multibody modelling (Component Mode Synthesis) by adopting a code considered as a reference in this research area (MSC.Adams).
This will require a finite element modelling and analysis (FEM, FEA) of one or more components, identified as significant by the research group (i.e. blades, tower), starting from the characteristics of the materials used and developed during WP B. Simulations on multibody model will be conducted in the time and frequency domain. The time domain analyses shall be the reference ones and those used for the optimization of the active control (both in terms of efficiency and fatigue behavior).
The frequency domain analyses will be granted exclusively to the evaluation of the fatigue behavior. Both families of analysis will be the subject of a phase of study aimed at the identification of hybrid approaches that allow to contain the calculation time of damage and at the same time to consider the full nonlinear behavior of the system.
Stress recovery and Fatigue behaviour evaluation
The analysis of the literature, that of historical series acquired by the research group in previous activities and the analysis numerical results obtained in phase WP A will allow to synthesize a series of loading conditions, significant and representative of the behavior of the generic WT.
The loading conditions will be characterized by amplitude, frequency and on a statistical basis, defining their representations by time histories and power spectral density functions. Stress states, resulting from multiple analyses, conducted both in time and frequency domains, will be recovered by modal approach.
The evaluation of the fatigue behavior will be addressed under the hypothesis of damage linear cumulation (i.e. Palmgren-Miner rule), in the stress domain (S-N) and in the high number of cycles (High Cycles Fatigue, HCF).
On-line monitoring of the fatigue phenomenon will be performed in conjunction with the output of Thread B, adopting the most relevant tools developed by the scientific community and by some of the proposers: Wohler strength curves, Miner's rule, Rainflow Counting method, Dirlik's formula, Braccesi's equivalent stress, Preumont's equivalent stress.
In this phase there will be the possibility to combine the two types of analyses (frequency and time approach) for the correct evaluation of the non-Gaussian stress state.