Abstract
During the aircraft’s maintenance, it is essential that its structural inspection as well as potential found damages to be assessed in an effective manner within a limited time frame. To reduce the required time, for the aforementioned procedure, an innovative tool is developed. For the first time, a structural integrity assessment tool integrates image processing algorithms and FE models. The tool processes data from Non Destructive Testing (NDT), via image processing algorithms, and then provide pieces of information regarding the residual strength of the examined component in an automated way. The data acquired, from the NDT, are interpreted using the threshold method, in order to generate an accurate map of the component with its damages (size and location). This information automatically feeds a parametric Finite Element (FE) model, which forms an FE model of the damaged component ready for analysis. The parametric FE model can construct models for isotropic and laminated monolithic components using the XFEM method and the Cohesive Zone Modelling (CZM) technique respectively. For the case of laminated components, Progressive Damage Modelling (PDM) is also considered. In this study, simple geometries as the upper and lower wing skin, are analysed under static tension or compression. Aim is to examine the effectiveness and feasibility of the developed tool. The main benefits obtained from the application of the tool is that the image processing data are manipulated automatically and fast providing all the information regarding the location and size of damage in the examined component. Moreover, from the obtained numerical results the strength reduction of the component can be predicted well, by just comparing them with the respective numerical results of the reference undamaged component. Overall, the developed tool is very promising, since time saving can be gained.
Highlights
From European Aviation Safety Agency (EASA) and Federal Administration Aviation (FAA)), [1], to inspect all aircraft components for possible defects/flaws, before they are assembled into the aircraft and they are periodically inspected throughout their useful life, using reliable and efficient Non Destructive Testing (NDT) techniques
The “wiener2” low-pass-filters an intensity image that has been degraded by constant power additive noise. “wiener2” uses a pixelwise adaptive Wiener method, [11], based on statistics estimated from a local neighbourhood of each pixel; (v) maximum entropy threshold theorem is applied to the filtered image; (vi) geometric characteristics are defined and calculated from the processed NDT image; number of defects, their centroid, their direction or area and coordinates with respect to the predefined coordinate system are calculated automatically; (vii) geometric characteristics of the damaged component are exported from the image processing algorithm to a text file, which can be used as an input file to ANSYS [12], where the numerical model is built
A parametric Finite Element (FE) model of the damaged component is developed within ANSYS software based on the output data of the image processing algorithm
Summary
From European Aviation Safety Agency (EASA) and Federal Administration Aviation (FAA)), [1], to inspect all aircraft components for possible defects/flaws, before they are assembled into the aircraft and they are periodically inspected throughout their useful life, using reliable and efficient NDT techniques. KAPPATOS essential, such an assessment to be performed since the DT addresses two essential points, concerning a damaged structure, (i) it determines fracture load for a specified defect size, and (ii) it predicts the required length of time for a sub-critical defect to grow to the size that causes fracture at a given load To this contribution, FE method has been employed for the solution of DT problems, since it provides high level of physics and suitable defect front representation for metallic and composite materials. It manipulates and exchanges the data between image processing algorithms and FE analyses in an automated manner The output of this tool are information that refer to the structural integrity (e.g. residual strength) of the examined aerospace component in a fast and efficient way. The analysis of the damaged composite plate has been upgraded with CZM with contact elements and PDM, for accurately predicting the onset and propagation of damage
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