I. Diamantakos

Simulation of the Electroimpulse De-Icing Process of Aircraft Wings

The electroimpulse de-icing system of an aircraft wing leading edge is investigated through the development of a methodology for the numerical simulation of the electroimpulse de-icing process. The principle of electroimpulse de-icing is that the ice is removed due to the leading edge local mechanical vibration, which is induced by an electromagnetic pulse. The numerical simulation methodology is based on a nonlinear transient three-dimensional stress analysis of the ice-covered wing, combined to a de-icing criterion that takes into consideration the tensile and shear stresses at the ice-skin interface. The developed methodology is verified on de-icing experimental tests of an aluminum plate. Afterwards, the methodology is applied to the prediction of de-icing of an aircraft wing leading edge. The dominant process parameters are determined to be the coil number and position, the ice thickness and coverage, the radius of wing curvature, and the electroimpulsive load amplitude. A parametric study is performed to determine the influence of the process parameters on the system effectiveness, defined as the percentage of the de-iced surface over the total leading edge surface. From the results of the parametric study, the possibilities of reducing the weight and energy consumption of the electroimpulse de-icing system can arise.

Adaptative Progressive Damage Modeling for Large-scale Composite Structures

Progressive damage modeling (PDM) is a well-established methodology for the prediction of damage initiation and evolution in composite structures. However, as conventional PDM methodology involves a large post-processing procedure, it is impractical for application in large-scale structures due to the high computational cost it requires. In this study, the local character of nonlinearity, due to the scale of the damage topology compared to the size of the entire structure, is exploited to propose proper modifications in the ‘classical’ PDM methodology. Specifically, the sub-modeling technique principles are combined and integrated in the PDM methodology and the appropriate modifications required are discussed. Furthermore, two damage prediction indices, which are related to the criticality of damage state at specific sub-areas (material layers) of the structure are introduced, in order to achieve significant reductions of the required computational time. Both the improvements make the application of PDM in large-scale composite structures practically feasible; this is demonstrated in the case of a generic composite shear joint whose numerical model comprises over a million degrees of freedom.

SHM System Based on ANN for Aeronautical Applications

In the present work a Structural Health Monitoring (SHM) system based on the use of Artificial Neural Network (ANN) method is presented that is suitable for aeronautical applications. The proposed methodology can be applied for the case of stiffened panels that are typical in aeronautical structures. The effect of sensor network layout, as well as noise applied during the training and prediction phase of the ANN application, is examined.

Analysis of Crack Patterns Under Three-Dimensional Residual Stress Field

Welding joining processes such as, laser-beam, friction-stir and arc welding lead to the development of residual stresses. Cracks developed at the influenced regions grow under the effect of these residual stresses and additional attention is required to be paid to the assessment of the structural integrity. In the present work three-dimensional Finite Element Analysis is utilized for the calculation of Stress Intensity Factors at cracks in welded components. The developed residual stress fields are calculated from the numerical simulation of the thermo-mechanical process. The fracture analysis methodology is initially validated by comparison of numerical results with existing analytical solutions for the case of a flat plate under typical welding residual stresses. Finally, the numerical procedure is applied to the study of the effect of residual stress fields on SIF values at cracks in welded stiffened panels.

An Integrated Methodology Assessing the Aging Behaviour of Aircraft Structures

The term ‘Ageing aircraft’ indicates an aircraft structure that is about to reach its original design goal. At this stage, the light alloy structures used in commercial aircraft are susceptible to Widespread Fatigue Damage (WFD) and possibly other deteriorating effects, such as corrosion damage. One typical form of WFD is Multiple Site Damage (MSD), which refers to the simultaneous existence of multiple interacting fatigue cracks at different sites of the same structural component (Fig.1). In the presence of MSD, critical crack sizes are greatly reduced, thus decreasing the residual strength of the structure below critical levels [1, 2] and leading to catastrophic failures due to the sudden cohesion of such interacting cracks [e.g. 3].