The Largest Open Access Portal of Nondestructive Testing (NDT)

From manufacturing to in-service inspections, aircraft structures are under close monitoring through Non-Destructive Testing (NDT) techniques. A large number of these inspections relies on human operators, especially in the context of in-service airplane maintenance. The resulting signal fluctuations and diagnosis errors can be limited by careful operator training, and must be taken into account anyway when it comes to the qualification of NDT procedures or the development of diagnosis assistant algorithms. Managing human-related variability requires a large number of experiments involving different operators and flawed parts. For expensive aeronautical structures, the related costs are drastically increased. To tackle this challenge, the concept of operational NDT simulator was proposed. The simulator is equivalent to a classical NDT equipment but the displayed signals are generated using a mathematical model: expensive flawed parts are replaced by a representative mock-up and defects are numerically added where required. The underlying model must ensure a realism and a computation speed high enough to replace reality. Classical approaches to numerical simulations cannot meet both requirements; data-driven modelling techniques are thus investigated. A proof of concept is proposed in the case of ultrasound inspections of composite structures. From the modelling perspective, the investigated strategy relies as much as possible on experimental data to ensure a high level of realism. Two different defect types are considered. A model of impact damage C-scans is built from a database of real impact inspections. The case of Flat Bottom Hole (FBH) defects is also studied with a meta-modelling approach applied on real data and enhanced by a physical knowledge. The resulting FBH model is able to efficiently replace real signals: certified NDT operators did not distinguish simulations from real signals. Thus, the operational NDT simulator can become a valuable tool to improve significantly any operations affected by human factors.

Possibilities of almost arbitrary complex shapes of additive manufactured (AM) components using 3D-printers enables design engineers to build lightweight structures with optimal force transmission. However, the freedom in design is often a challenge for non-destructive testing, especially for highly-stressed AM-components with increased complexity. Thus, reliable quality assurance is an important topic to ensure highest quality in aeronautics and space industry. There are only a few NDT methods to be applied on such structures. Computed Tomography (CT) and Digital X-Ray techniques are the most important ones offering rich information of the outer geometrical metrology together with a 3-dimensional look inside the component. Moreover, quantitative analysis of volumetric characteristics can be iteratively looped with design offices. The requirements regarding permitted imperfection of aeronautic components are depending on the component purpose. There are different acceptance levels for pores in aeronautic components. Finding pores with e. g. 200 µm in diameter may lead to large CT-data, which are challenging in acquisition, reconstruction, evaluation and storage. A CT-scan of a (250 mm)3 component with a nominal voxel size of 47 µm will result in a reconstructed dataset of approximately 301 GB. The smallest pore to be found in this example will be mapped with only 33 voxels. Finding the right approach to obtain highest detection reliability of small defects in large CT-datasets is the key for time and cost saving in CT-inspection of additive manufactured components. Different ways of manual and semi-automated evaluation as well as their possibilities and limits will be discussed.

In 1893 the maiden flight of the glider Normalsegelapparat of Otto Lilienthal took place. One year later the serial production started and at least eight gliders were sold for 500 Mark. Today four are remaining. One of them belongs to the Deutsches Museum and it was flown by Otto Lilienthal himself. The present original fragments from the glider are in a poor condition state. The aim of this study is to visualize by Computed Tomography voids and deterioration of the inner structure of wooden fragments. Based on this scientific investigation the stability of the glider’s structure will be estimated and a concept for conservation treatment and exhibition will be developed. This interdisciplinary project was a collaboration between Deutsches Museum, Technical University of Munich, Airbus Materials X, Airbus Helicopters, and TESTIA. This paper will present the results from two fragments.