Analysis-Driven Design Optimization of a SMA-Based Slat-Cove Filler for Aeroacoustic Noise Reduction

Abstract

Airframe noise is a significant component of environmental noise in the vicinity of airports. The noise associated with the leading-edge slat of typical transport aircraft is a prominent source of airframe noise. Previous work suggests that a slat-cove filler (SCF) may be an effective noise treatment. Hence, development and optimization of a practical slat-cove-filler structure is a priority. The objectives of this work are to optimize the design of a functioning SCF that incorporates superelastic shape memory alloy (SMA) materials as flexures that permit the deformations involved in the configuration change. The goal of the optimization is to minimize the actuation force needed to retract the slat-SCF assembly while satisfying constraints on the maximum SMA stress and on the SCF deflection under static aerodynamic pressure loads, while also satisfying the condition that the SCF self-deploy during slat extension. A finite element analysis model based on a physical bench-top model is created in Abaqus such that automated iterative analysis of the design could be performed. In order to achieve an optimized design, several design variables associated with the current SCF configuration are considered, such as the thicknesses of SMA flexures and the dimensions of various components, SMA and conventional. Design of experiment (DOE) studies are performed to investigate structural response to an aerodynamic pressure load and to slat retraction and deployment. DOE results are then used to inform the optimization process, which determines a design minimizing actuator forces while satisfying the required constraints.

Development of a SMA-Based, Slat-Gap Filler for Airframe Noise Reduction

“…The SCF concept has been shown, both experimentally 10,11 and computationally 12,13 to significantly reduce slat noise. Recent work has been done to demonstrate the feasibility of developing an autonomous (passive) SCF device 20,21 .…”

Computational Modeling of a Mechanized Bench-Top Apparatus for Leading-Edge Slat Noise Treatment Device Prototypes

“…Multipiece SCF assemblies, consisting of two SMA flexures separated by a stiffer mid-link, were considered in those studies because of the possibility for controlling the deformation distribution and, consequently, the stowage timing. Although the optimal SCF configuration for this 2D airframe case proved to be a monolithic (one-piece), superelastic SMA with the shortest hinge possible, other SCF configurations that satisfied the application requirements were found in the course of the parametric study and optimization 13,14 . Four of these suboptimal but operable configurations (Mono-2 through Multi-3) are shown with the optimal design (Mono-1) in Figure 11, where the reference lines and dimensions are consistent with the parametric computational model used for the optimization.…”

“…A concept consisting of one or more superelastic shape memory alloy (SMA) components, shape set to the deployed configuration, was found to satisfy the application requirements and provide implementation feasibility. Further work was done to optimize the superelastic-SMA, SCF design to minimize the actuation authority required to stow the structure while satisfying steady-aerodynamic-load and other requirements 13,14 . Recent work has studied means to further reduce actuation requirements 15 .…”

“…The slat-cove filler, shown in Figure 8, was attached to the slat near the cusp, or lower trailing edge, by a hinge and at the upper trailing edge by a riveted lap joint. As mentioned in Section II, simplified physical and computational models were used for parametric study and optimization of the SCF for this 2D airframe, where optimization entailed minimizing the actuator authority required to stow the SCF while satisfying static load and other constraints [12][13][14] . Multipiece SCF assemblies, consisting of two SMA flexures separated by a stiffer mid-link, were considered in those studies because of the possibility for controlling the deformation distribution and, consequently, the stowage timing.…”

“…Simplified computational models were previously developed to analyze the SCF [12][13][14][15][16] and SGF 24 performance under aerodynamic and retract/deploy loads. The objectives of the present work were to develop finite element (FE) models of the mechanized benchtop SCF and SGF apparatus for refined prediction of the structural performance, practical estimation of actuator authority requirements, and eventual comparison with experimental results.…”