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WING STRUCTURAL TEST DEVELOPMENT METHOD

Periodic Report Summary 2 - WISDOM (WING STRUCTURAL TEST DEVELOPMENT METHOD)

Project Context and Objectives:
WISDOM main objective is to approach an innovative and reliable solution for the design, manufacturing, set up and commissioning and performance & analysis of the structural test of the port and starboard outer wing sections needed for flight tests of natural laminar flow on the SFWA flight test demonstrator under Clean Sky Program.
The main requirement for this wing structural part is based on their high dimensional stability and tight geometrical tolerances to compliance with surface quality for a natural laminar flow condition, and therefore stability control and manufacturing precision over the test bench tools to be designed and manufactured shall consider this, avoiding as much as possible interfaces with the specimen upper surface.
The test procedure is based in a Self-supporting test rig with flexible and adaptable plug and play loads introduction method with minimum specimen interface needs and wireless connection for data recording
The main requirement for this wing structural part is based on their high dimensional stability and tight geometrical tolerances to compliance with surface quality for a natural laminar flow condition, and therefore stability control and manufacturing precision over the test bench tools to be designed and manufactured shall consider this, avoiding as much as possible interfaces with the specimen upper surface.
The test procedure is based in a test rig with flexible and adaptable plug and play loads introduction method with minimum specimen interface needs and wireless connection for data recording.
The challenge of this project is to define the test method necessary to demonstrate that major components tests can be performed on flight test aircraft.
Currently wing bend test methods are destructive, incurring in high cost. The main goal of this proposal is to develop a NON-DESTRUCTIVE method for wing bend tests, innovating in minimum test bench-wing interfaces, Non destructive inspection methods (infrared thermography) and wireless data recording.


Project Results:
From the beginning of WISDOM Project, the Consortium members (SerTec, CTA and TEAMS) have been working with the idea to design and perform a Bending Up Test applying new concepts and leaning on new technologies available at the moment in order to reduce test time, achieve an environmental friendly test avoiding hydraulic applications, new specimen inspection methods, new way of connection, follow up test behavior and reception of the result of the test by the authorized people independently of their location and time, all of this without decreasing the security of the people involved when the test is running and safety of the specimen itself.
From design and stress engineering point of view, test tooling have been development and have passed several quality gates in accordance with Topic Manager and Airbus staff to ensure the rig tooling is suitable for carrying out the test, will not damage the specimen and accomplish with all the requirements for this project. Nowadays, tooling has reach the PDR maturity level, with all the actions at Consortium side solved.
Each of the parts that comprise tooling have been calculated in order to study their stress level and designed in order to have a security factor of 2 minimum at the critical load case to prevent breakage of the tooling during test. All main assemblies have been calculated (BLADE whiffletrees, A340 wing attachment whiffletrees, Test slab connection structures, intermediate structures, crane interface structures,…) and the results showed in several stress documents uploaded in the web application FEM calculations PDR documents deliverables.
As design work, several documentation has been issued for PDR quality Gate, such as:
• Assembly procedure manual in a draft version for PDR has been issued, describing the method and auxiliary tooling needed to build up all the elements the test rig. This document was required to pass the PDR.
• Test Campaign Description document for PDR, describing the test campaign proposed by the consortium, Test preparation and Test conduct. This document was mandatory to pass the PDR.
• Ergonomic studies for strain gauges installation inside BLADE wing box. Accessible and not accessible areas declaration.
These documents will be edited and will be frozen at CDR Quality Gate, to incorporate all the possible modifications the tooling could suffer till reach its final design phase.
Regarding new technologies, from the start of the project, the Consortium members have been studying, developing and testing several applications to be implemented in WISDOM project. The main new technologies are:
- New Load Introduction Systems: The proposed method is to use electrical devices based on winches. This method is very convenient when used in only pulling tests. The High Precision Servo-controlled Winches (HPSW) will be capable of controlling the load by using Brushless Motors for winches actuation while using appropriate motor driver for controlling. The servo-loop will be closed externally using the typical Test Controllers as those provided by the well known brands as MTS o FCS/MOOG. Consequently there are two closed loops one internal to the motor driver and one external as described previously. This system is clean, because it use electrical power instead of hydraulics, and the power needed can be distributed along the electrical network in a better and more efficient way. In order to avoid any kind o risk if the supply fails it will be implemented a controlled shutdown using the energy applied to the test specimen. The specimen when is loaded works like a spring. The potential energy is used to unload the own specimen using autonomous system working with batteries to allow the specimen unloading using electric brakes to unload smoothly the test specimen. At this stage, all the studies have been performed, and the elements of the systems have been selected. A test for one of this winch system will be carried out at SerTec facilities during CTR stage.
- Remote Data Acquisition Reception: The follow up of the test could be done in remote thanks to the system LINCE developed by TEAMS. LINCE is a tool for test follow-up which main advantages are:
• Data and video synchronization
• Calculated channels
• Independent access for each customer
• Replay option
• Data stored in the application and accessible to the customer
• Multi-platform free solution for the customer, there is no need to install proprietary applications in the customer
Normally during a test like the one developed in this proposal various stress engineers from different locations have to travel from their office to the place where the test is performed, that mean big costs in transportation which can be avoided if a tool like the one described in this WP can be used during the campaign.
To make this tool fully functional new functions will be developed. The deliverable a new version of this tool will be issued with new functions like the one listed below:
• Inspection & Damages reports available at the application. Document repository
• Unlimited number of simultaneous tests
• Instrumentation drawings available in the application.
• Security protocols implementation for a secure communication and data interchange
A functional test of the application will be prepared by TEAMS to be done at CTR stage.

- Infrared Thermography Applications: The infrared thermography, together with Thermoelastic Stress Analysis may be used in the evaluation of stress distribution in aeronautical components under mechanical loads. The most recent studies show that different methods of Thermoelastic Stress Analysis are capable of explaining the manner in which damage initiates and propagates in composite materials. With this ability of detection and analysis techniques it is possible a timely intervention and repair to prevent component failure.
The data recorded during the structural tests taken by gauges, belong to specific points where each gauge is situated, and therefore there may be deviations from the finite element model of tension design. When obtaining an image by infrared thermography of the behavior of a wide area, it can achieve the following advantages:
• Visualization of the level of tensions of a large area in just one image, which facilitates the interpretation of the results, since the result is a map with color coded grades of tension. This contrasts with the numerical values offered by the gauges.
• Verification of the results obtained with finite element models. This verification may enable a rapid change in the structural test configuration to make it more realistic or soon decide on a design change to avoid future higher costs.
• Optimization in the use of gauges: Depending on the tension field measured by IRT it will be possible to correct the position of the gauges, to place them in points of greatest interest, and not far away, as may indicate the theoretical model. Furthermore, the use of IRT will help put the just necessary gauges, instead of using too many of them to be sure to cover as many points as possible, with the associated additional cost.
• Improvement of calculations and design: based on a better understanding of the stress field by the visualization of the behavior of the specimen during the mechanical test it could lead to improved designs and increased safety margins reducing weights
All the studies have been carried out yet and a test of the application will be prepared by CTA to be done at CTR stage.
- Wireless Data Acquisition System: For this kind of test it has been investigated and implemented a contactless system for deflection measurement. The system is based on local GPS system but not only. The main idea is provide a 3D map of the deflecting surface in order to be easily compared with FEM models.
The aim is to implement contactless measuring systems, besides the main idea to install the local GPS system other measuring techniques can be used.
• Optical measuring systems based on stereo correlation which can provide 3D surface coordinates and displacements as well as surface strain values.
• Optical measuring systems based on the application of photoelastic coatings. That extends the classical procedures of model photoelasticity to the measurement of surface strains in opaque two and three dimensional models made of any material. The coating is a thin layer of birefringent material (usually a polymer) that is bonded integrally to the flat or curved surfaces of the specimen being analyzed for stress. When the specimen is loaded, the surface strains are transmitted to the coating, reproducing the specimen strain field in the coating. The use of high definition cameras could allow the measurement of large areas into the specimen.
A second objective of this work package is the utilization of a distributed and wireless acquisition system. Traditionally the use of wireless data acquisition systems had been avoided mainly due to limitations into the transmissions rates due to the inherent bandwidth limitation associated with the standards used in the past. However the last advances in the wireless protocols and the new industry standards could lead to new opportunities in this field
All the studies have been carried out yet and a test of the application will be prepared by TEAMS to be done at CTR stage.

Potential Impact:
The WISDOM project addresses the JTI-CS-2012-02-SFWA-03-010 topic “BLADE wing structural test to derive test data for subsequent validation of GFEM modeling” within the SFWA ITD of Clean Sky. Therefore, the project will contribute to this ITD expected environmental impact which consists of putting greener products into the market that:
• Reduce the medium and long range aircraft fuel burn and aircraft emissions by around 10
to 20%.
• Reduce the medium and long range aircraft noise by 5 to 10 dB.
Furthermore, the project will contribute in terms of socioeconomic impact to ACARE’s latest goal
of making the European aircraft industry meet society’s needs and win global leadership.

Impact of the project on the environment
Many studies have concluded the effectiveness of optimizing wing shape in order to delay transition from laminar to turbulent flow and thus reduce aircraft drag. Thus, estimations of a 20% reduction in drag through NLF technology have been presented. Benefits associated to drag reduction are a decrease in fuel burn a well as aircraft emissions and noise. Possible fuel savings of up to 30% for subsonic commercial aircraft have been suggested through successful NLF system development. An equivalent amount of reduction in CO2 emissions per passenger and km could be expected. A 58% decrease in NOx emissions and 16 dB reduction in noise (together with a 44% decrease in fuel burn) through combination of advanced composites, LF and very high bypass turbofans has been proved by Boeing SUGAR team on a 737 size airliner.

Socioeconomic impact of the project
Air transport is a strategic sector for the Europe economy. Studies have shown that this industry accounts for approximately 2.5% of GDP, creates over 3 million jobs (direct and indirect) and contributes in excess of 30Bn to a positive trade balance for Europe. Moreover, based on projected growth over the next twenty years air transport could contribute an additional 1.8% of GDP. However, gradual worsening of the global economic situation, euro-dollar exchange rate, cost of oil and emerging new competitors are forcing the European aerospace sector to continuous efforts to maintain its position. Since despite extensive research both in Europe and in the US no usable LF control system has yet found its way on to commercial aircrafts, the WISDOM project will provide increased and differentiated technological capabilities to the European aircraft industry. The expected results will not only benefit aircraft manufacturers’ competitiveness but also their suppliers’, many of them SME’s who are experiencing a fierce concurrence from low cost competitors. The project will also contribute to sustainable growth requested by European citizens since highly qualified jobs will be maintained or created to fabricate new environmentally friendly products.