A Fatigue Life Reliability-based Design Optimization of a Slat Track using Mesh Morphing

Although the aerospace production process is much better controlled than the process in other industries, it remains true that very small manufacturing tolerances exist in the geometrical parameters (flange thicknesses, hole diameters,. ..). In the current design process, the effect of this manufacturing variability on the structural durability and safety cannot be accurately assessed and is hence compensated for by applying safety factors. This is not an ideal situation, as it may lead to slightly over-designed structures. A much more promising approach is to include probabilistic models of design variables into the mechanical simulation process. Then, with a new methodology based on reliability analysis, engineers can obtain a better understanding of the actual effect of the manufacturing tolerances. Based on the analysis results, the robustness and reliability of the design can be assessed and improved if needed. In this paper, the above-mentioned probabilistic approach is demonstrated on a slat track structure. Measurements of different geometrical properties have been collected during the manufacturing process and their variability has been characterized probabilistically with statistical models. Then, a reliability analysis has been carried out using morphing technology and fatigue life predictions with an industrial-sized FE model of the slat track to assess the reliability of the structure in terms of fatigue life. The outcome of the analysis consists of a probabilistic model of the fatigue life, given the variability in the geo-metrical parameters. This analysis not only provides a better insight in the effect of variability in the fatigue life prediction, but also provides sensitivity measurements of the design parameters on the final performance of the structure. These results provide guidelines to improve structural designs and manufacturing tolerances, by using a reliability-based design optimization procedure. A powerful tool is thus obtained to reduce design conservatism while maintaining and even improving structural safety.