Probabilistic method for impact load estimation by Stochastic Model – a Fan Blade Off event

The front bearing mount structure in an aero engine has been severely loaded under the fan blade off (FBO) event since imbalance forces at high amplitude but low frequency is transformed to the engine front mount structure. The bearing mount structural forces are estimated by an integrated implicit-explicit analysis process of whole engine model of an aero engine. Since there are many dependent factors which are governing those predicted loads, experimental evidence on FBO is becoming necessary to validate the model used for the load prediction which is more expensive and also time consuming. This paper aims to discuss the above mentioned issues.

The current paper deals with the high impact but low probability nature of FBO load prediction on the bearing mount structure by stochastic approach which could be replaced for FBO experiments which is highly essential for current economic conditions. Several influential factors on the predicted loads have been chosen in the stochastic model and sensitive analysis has also been performed to bring down the variation involved in the predicted load.

The predicted load by proposed stochastic model is then compared with the experimental results. The conclusion on the predicted load with various dependent influential factors is matching well with certain value of damage factor from planned FBO test event.

Limitation of this paper could be that it does not cover with range of load amplitude and is only applicable for civil small and medium engines.

The high amplitude but low frequency load pattern is assessed with impact condition by stochastic model.

Combining experimental and probabilistic load prediction was never done before and read across from previous engine test program could be effectively performed with stochastic model approach.