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Cost reduction by advanced non-destructive inspection of aeronautical structures

Exploitable results

The current worldwide recession in the aeronautical industry forces many aircraft operators to postpone investments in new aircrafts and consequently stretch the lifetime of their existing fleet. Therefore, the European aeronautical industry nowadays sees itself faced with two main challenges: safe operation of an ageing aircraft fleet, and cost effective production and maintenance. For both areas, the aeronautical industry has the responsibility to provide the methods that enable the operators to offer safe and cost effective services to their passengers. One of the approaches the industry has chosen to deal with these challenges is the application of advanced materials. These materials offer the opportunity of reduced weight and more efficient production, lowering both operational and production costs. They require however another approach with respect to non-destructive testing (NDT): material behaviour and defect types differ largely from more conventional, metallic structures. At the same time stretched maintenance intervals and extended aircraft lifetime, have made quantitative detection of cracks and corrosion in metallic structures highly desirable. Non-destructive inspection requirements can have a large impact on aircraft production and operation. This calls for efficient NDT methods that don’t require long down times for in-service inspections, and are fast and reliable for production inspection. No single method can fulfil all requirements. In some cases the solution lies in the development of speedy full field methods that can inspect large areas. In other cases sophisticated signal processing for extraction of defect information from the measured signals yields the best result. In addition it is envisaged that an approach using knowledge based diagnosis systems will offer increased inspection reliability. This project developed and applied the NDT techniques that are most promising for the aeronautical industry and potentially for other industries. The developments were focused on 3 distinctive problem areas: -Reliable inspection methods for ageing aircraft. -Fast non-contact NDT methods for production inspection. -Rapid full field methods for in service inspection of advanced materials. These developments were enhanced by a separate task directed to the establishment of knowledge-based diagnosis systems combined with data fusion. The task 1 comprised development and application studies of eddy currents, laser ultrasonics and thermography. Much attention was paid to the development of new eddy current techniques, due to the vast amount of urgent problems that can potentially be solved with this technique such as hidden crack and quantitative corrosion detection. To this aim the multi-frequency approach, the introduction of C-scanning and the application of neural networks for signal analysis are very promising. The application of laser ultrasonics to aircraft corrosion problems was systematically investigated for the first time in Europe. The combination of thermography with pulsed excitation and the application of neural networks provide a fast corrosion detection system. The main industrial objective of the task 2 was to suitably enhance the production NDT methods in order to perform large area coverage. This was achieved by researching and developing potential non-contact inspection techniques. This included the real time full field methods of thermography and shearography for the inspection of large composite components, expert radiography system for the optimisation of development and production of composite and metallic structures, air coupled ultrasound for large aerofoil composite configurations and laser generated ultrasonics for complex geometry applications. Significant developments, comprehensive evaluation and demonstration of these techniques were carried out; advantages and inconveniences have been drawn. The task 3 aimed at the development of rapid single-sided access detection methods for quantification of defects in aeronautical composite parts, without removal or special surface preparation. On site demonstration was carried out with the selected methods to which were added methods developed in Task 1 and 2 respectively multi-frequency eddy currents and shearography. Non-contact ultrasonics and thermography are most promising with regard to these industrial requirements. Task 4 aimed at specifying the software and hardware requirements for a NDT diagnosis tool that enables the combination of the inspection results from manifold NDT methods and CAD data with the idea of supporting and standardising the diagnosis criteria. The combination of NDT data with CAD data was carried out in such a way that the information can be used in a synthetic approach to reach a diagnosis. Some application examples were tested and data fusion successfully applied to x-rays and infrared thermography inspection data together with CAD Data.
The current worldwide recession in the aeronautical industry forces many aircraft operators to postpone investments in new aircrafts and consequently stretch the lifetime of their existing fleet. Therefore, the European aeronautical industry nowadays sees itself faced with two main challenges: safe operation of an ageing aircraft fleet, and cost effective production and maintenance. For both areas, the aeronautical industry has the responsibility to provide the methods that enable the operators to offer safe and cost effective services to their passengers. One of the approaches the industry has chosen to deal with these challenges is the application of advanced materials. These materials offer the opportunity of reduced weight and more efficient production, lowering both operational and production costs. They require however another approach with respect to non-destructive testing (NDT): material behaviour and defect types differ largely from more conventional, metallic structures. At the same time stretched maintenance intervals and extended aircraft lifetime have made quantitative detection of cracks and corrosion in metallic structures highly desirable. Non-destructive inspection requirements can have a large impact on aircraft production and operation. This calls for efficient NDT methods that don’t require long down times for in-service inspections, and are fast and reliable for production inspection. No single method can fulfill all requirements. In some cases the solution lies in the development of speedy full field methods that can inspect large areas. In other cases sophisticated signal processing for extraction of defect information from the measured signals yields the best result. In addition it is envisaged that an approach using knowledge based diagnosis systems will offer increased inspection reliability. In this project were developed and applied the NDT techniques that are most promising for the aeronautical industry and potentially for other industries. The developments were focused on 3 distinctive problem areas: - Reliable inspection methods for ageing aircraft. - Fast non-contact NDT methods for production inspection. - Rapid full field methods for in service inspection of advanced materials. These developments were enhanced by a separate task directed to the establishment of knowledge based diagnosis systems combined with data fusion. Task 1 comprised development and application studies of eddy currents, laser ultrasonics and thermography. Much attention was paid to the development of new eddy current techniques, due to the vast amount of urgent problems that can potentially be solved with this technique such as hidden crack and quantitative corrosion detection. To this aim the multi-frequency approach, the introduction of C-scanning and the application of neural networks for signal analysis are very promising. The application of laser ultrasonics to aircraft corrosion problems was systematically investigated for the first time in Europe. The combination of thermography with pulsed excitation and the application of neural networks provide a fast corrosion detection system. The main industrial objective of task 2 was to suitably enhance the production NDT methods in order to perform large area coverage. This was achieved by researching and developing potential non-contact inspection techniques. This included the real time full field methods of thermography and shearography for the inspection of large composite components, expert radiography system for the optimisation of development and production of composite and metallic structures, air coupled ultrasound for large aerofoil composite configurations and laser generated ultrasonics for complex geometry applications. Significant developments, comprehensive evaluation and demonstration of these techniques were carried out; advantages and inconvenience have been drawn. Task 3 aimed at the development of rapid single-sided access detection methods for quantification of defects in aeronautical composite parts, without removal or special surface preparation. On site demonstration was carried out with the selected methods to which were added methods developed in Task 1 and 2, respectively, multi-frequency eddy currents and shearography. Non-contact ultrasonics and thermography are most promising with regard to these industrial requirements. Task 4 aimed at specifying the software and hardware requirements for a NDT diagnosis tool that enables the combination of the inspection results from manifold NDT methods and CAD data with the idea of supporting and standardising the diagnosis criteria. The combination of NDT data with CAD data was carried out in such a way that the information can be used in a synthetic approach to reach a diagnosis. Some application examples were tested and data fusion successfully applied to x-rays and infrared thermography inspection data together with CAD data.