Papers by Keyword: Modal Frequencies

Abstract: Woven fiber reinforced polymer composites plays major role in structural applications. Structures subjected to dynamic situations, this leads to increased attention in finding characteristic behaviour/performance of FRP composites beams under vibrating conditions. The objective of this work is to understand and investigate the influence of cross sectional shapes of beams on successive vibration resonance frequencies and its damping performance under cantilever end conditions. The beams were fabricated by hand lay-up method in two different modulus material and cross sections like I and channel; maintaining uniform cross sectional area and moment of inertia apart from length of the beams using woven carbon fibre. The investigation was performed by impulse frequency response method using standard test procedure on low modulus Glass/epoxy composite beams and compared with high modulus Carbon/epoxy beams. Frequency response curve of I and channel shaped beams were compared for their damping performance. The modal frequencies of all fabricated beams were obtained using MEScopeVES® software and modal resonant frequencies, loss factor were compared against shapes.

Abstract: This study investigates a possibility for representing, interpreting and visualising the vibration response of aircraft panels using time domain measurements. The aircraft panels are modelled as thin orthotropic plates and their vibration response is simulated using FE modelling. The vibration response of a thin aluminium panel is simulated using FE modelling. The first ten resonant frequencies are estimated for the FE model and for the dynamically tested panel. They were found to show somewhat low sensitivity to damage. Then the simulated vibration response of the panel is transformed and expanded in a new phase space. This presents an alternative way to study and analyse the dynamics of a structure. A two dimensional phase space is used in this investigation. Thus instead of studying the single dimension measured vibration characteristics one is faced with expanded two dimensional variables which can be visualised and this facilitates the comparison between the damaged and the non-damage states.

Abstract: This study investigates the possibilities for damage detection and location using the vibration response of an aircraft wing. A simplified finite element model of an aircraft wing is used to model its vibration response. The model is subjected to modal analysis- its natural frequencies are estimated and the mode shapes are determined. Two types of damage are considered - localised and distributed. The wing model is divided into a number of volumes. The goal of the study is to investigate the possibility to use the vibration response of an aircraft wing and especially its modal characteristics for the purposes of damage detection. So we’ll be trying to find suitable features, which can be used to detect damage and restrict it to one of the introduced volumes. The sensitivity of the modal frequencies of the model to damage in different locations is studied. Some general trends in the behaviour of these frequencies with change of the damage location are investigated. The utilization of the modal frequencies for detecting damage in a certain part of the wing is discussed

Abstract: This work investigates the use of two different vibration-based methods for health monitoring of aircraft wings. A finite element model of a simplified wing is used to model and predict the vibration response of an aircraft wing in an intact condition and in the presence of different types and levels of damage. Two main types of damage are considered- cracks and distributed damage. This study first explores the sensitivity of the lower modal frequencies to different damage levels of the studied types. Then the employment of the frequency response functions subjected to principal components analysis is discussed. This is an early model-based study which is intended to establish if the considered procedures can be used as damage detection tools.