Periodic Reporting for period 1 - FADAMES (Fatigue damage at mesoscopic level. Fatigue life prediction in conjunction with acoustic emission signals)
Reporting period: 2018-07-01 to 2020-06-30
Fatigue damage occurs in three stages: crack initiation, growth from small to short and long crack and final fracture of the component. The first two stages, which cover most of the fatigue life, are dominated by the interaction with microstructural features of the material. Reference studies describe the physical mechanisms of fatigue crack initiation based on the persistent slip bands which are formed at grain level and cause an accumulation of plastic deformation. In most cases, the prediction models for fatigue crack initiation based on physical damage mechanisms have been developed and applied on simplified computational models incorporating several grains with well-defined crystallographic characteristics (called Representative Volume Elements – RVE) which are then subjected to simple loads.
A current problem for accurate prediction of fatigue damage of structural components is the implementation of physical damage mechanism-based models for a real loading case characterized by a multiaxial stress/strain state. This is the primary area of investigation for this project. On the other hand, the accumulation of plastic deformation occurs with the release of strain energy, that can be captured using the acoustic emission technique. In this context, the objectives of the action are summarized as follows: 1) Development of a novel concept for the evaluation and prediction of fatigue damage. Fundamentally the concept consists of correlating the real stress/strain state with the physical mechanisms of material degradation at mesoscopic level; 2) Link results of the concept with detected AE signatures during experimental validation testing; 3) Develop the researcher’s knowledge and ability so he is recognized as an established independent researcher whilst benefiting the Cardiff University knowledge of the AE techniques to industry and academia.
 https://www.theguardian.com/business/2018/apr/17/philadelphia-plane-emergency-southwest-landing-engine-explosion-latest ;
 https://www.theengineer.co.uk/rolls-royce-problems-trent-1000/ ;
Overall, the project contributes both to the understanding and characterization of fatigue damage mechanisms, and to the failure’s prevention through predictive analysis. All these have a great economic impact by designing reliable safety components and also socially through the significant contribution in ensuring and maintaining the safety and comfort of the population.