Monitor Points Method for Loads Recovery in Static/Dynamic Aeroelasticity Analysis with Hybrid Airframe Representation 2013-01-2142

With the high design/performance requirements in modern aircrafts, the need for a flexible airframe structural modeling strategy during the different phases of the airframe development process becomes a paramount. Hybrid structural modeling is a technique that is used for aircraft structural representation in which several Finite Element Modeling concepts are employed to model different parts of the airframe. Among others, the Direct Matrix Input at a Grid-Point (DMIG) approach has shown superiority in developing high fidelity, yet, simplified Finite Element Models (FEM's). While the deformation approach is a common choice for loads recovery in structures represented by stick models, using structural models simulated by the DMIG representation requires the adoption of a different approach for loads recovery applications, namely, the momentum approach.

In this paper, the Monitor Points (MP) Method is introduced as an efficient methodology for loads recovery in static and dynamic Aeroelasticity analysis with hybrid airframe representation. MP method is a function provided in MSC NASTRAN that hinges on the momentum approach for loads recovery as it enables the superposition of applied loads at a user defined point and transformed into a user defined coordinate system. Here, the hybrid model is used to generate accurate predictions of the aircraft structural kinematics in flight which by its turn generates accurate profiles for the encountered aerodynamic and inertia loads. The MP method is then employed to generate high fidelity distributed loads necessary to predict the different critical load cases that generate the aircraft's loads envelop.

A sensitivity analysis is conducted which showed the high convergence of the presented methodology as it is less sensitive to modal truncation errors compared to loads recovery methods that hinge on the deformation approach.