Reliability-Based Design of a Slat-Track Fatigue LifeUsing Mesh Morphing Technology

Abstract

Although the aerospace production process is much better controlled than in other industries, it remains true that very small manufacturing tolerances exist in the geometrical parameters such as flange thickness and 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, because it may lead to slightly overdesigned structures. A much more promising approach is to include probabilistic models of design variables into the mechanical simulation process. With a new methodology based on reliability analysis, engineers can obtain a better understanding of the actual effect of the manufacturing tolerances and of variability in material properties. Based on the analysis results, the robustness and reliability of the design can be assessed and improved if needed. In this paper, the aforementioned probabilistic approach is demonstrated on a slat-track structure. Measurements of different geometrical properties were collected during the manufacturing process and their variability was characterized probabilistically with statistical models. Then a reliability analysis was carried out using mesh morphing technology and fatigue life predictions with an industrial-sized finite element 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 structural performance (e.g., fatigue life for the slat track), given the variability in the geometrical parameters. Then a reliability-based design optimization procedure was carried out to improve the design of the slat track while maintaining the same reliability of the nominal design.