Strut-Braced Wing Modelling with a Reduced Order Beam Model

In recent years there has been much interest in the study of strut-braced wings, as they potentially offer the opportunity to design lightweight wings with increased wingspan. This work includes NASA’s development of a strut-based configuration as part of the Subsonic Ultra Green Aircraft Research (SUGAR) project. Optimisation strategies, based on linear structural models have been proposed to size such a wing. Here, a simple sizing study is conducted on the SUGAR planform using empirical formula and a linear Nastran structural model. The resulting wing is then analysed using a novel nonlinear structural solver to assess the effect of including geometric nonlinearities on the predicted wing response. It is shown that for the maximum stress levels considered geometric nonlinearity has only a slight effect on the deflections of the sized wingmodel.<br/

Particle swarm optimization with sequential niche technique for dynamic finite element model updating

Peer reviewedPostprin

On multi-site damage identification using single-site training data

This paper proposes a methodology for developing multi-site damage location systems for engineering structures that can be trained using single-site damaged state data only. The methodology involves training a sequence of binary classifiers based upon single-site damage data and combining the developed classifiers into a robust multi-class damage locator. In this way, the multi-site damage identification problem may be decomposed into a sequence of binary decisions. In this paper Support Vector Classifiers are adopted as the means of making these binary decisions. The proposed methodology represents an advancement on the state of the art in the field of multi-site damage identification which require either: (1) full damaged state data from single- and multi-site damage cases or (2) the development of a physics-based model to make multi-site model predictions. The potential benefit of the proposed methodology is that a significantly reduced number of recorded damage states may be required in order to train a multi-site damage locator without recourse to physics-based model predictions. In this paper it is first demonstrated that Support Vector Classification represents an appropriate approach to the multi-site damage location problem, with methods for combining binary classifiers discussed. Next, the proposed methodology is demonstrated and evaluated through application to a real engineering structure – a Piper Tomahawk trainer aircraft wing – with its performance compared to classifiers trained using the full damaged-state dataset

Experimental and Numerical Investigation of Rotor-Rotor Dynamic Interactions in a Tilting Multirotor System

This study aims to study rotor-rotor dynamic interactions in a tilting multirotor test rig through a combined experimental and numerical investigation. The rig was dynamically scaled to simulate the ordering and relative spacing of leading structural modes observed in NASA's X-57 DEP wing. An experimental modal analysis was performed under stationary and rotational conditions with shaker excitation, and the results were compared to a beam element based model simulated in MSC NASTRAN. The gyroscopic effects arising from propeller spin were introduced in the model using the Rotordynamics toolbox in MSC NASTRAN. The model was able to accurately represent the baseline structural dynamic response to within ±5% of experimental values and also captured key dynamic features such as mode frequency divergence, whirling and veering across the investigated rotor speed range. The dual rotor configuration, in contrast to the single rotor case, exhibited additional mode divergence, several distinct overlapping veering regions, and switching of mode shape properties. These results show that the coupled dual rotor configuration produces rich interaction-driven modal phenomena that transcend those encountered in isolated cases. The validated modelling method provides a basis for identifying such regimes and examining the effect of rotor spacing on the emergence and development of interaction-driven behaviour in multirotor systems

Experimental and numerical approaches for structural assessment in new footbridge designs (SFRSCC–GFPR hybrid structure)

Within the civil engineering field, the use of the Finite Element Method has acquired a significant importance, since numerical simulations have been employed in a broad field, which encloses the design, analysis and prediction of the structural behaviour of constructions and infrastructures. Nevertheless, these mathematical simulations can only be useful if all the mechanical properties of the materials, boundary conditions and damages are properly modelled. Therefore, it is required not only experimental data (static and/or dynamic tests) to provide references parameters, but also robust calibration methods able to model damage or other special structural conditions. The present paper addresses the model calibration of a footbridge bridge tested with static loads and ambient vibrations. Damage assessment was also carried out based on a hybrid numerical procedure, which combines discrete damage functions with sets of piecewise linear damage functions. Results from the model calibration shows that the model reproduces with good accuracy the experimental behaviour of the bridge