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Development of Non-destructive Inspection Approaches for Automatic detection and MONitoring of Damage evolution

Final Report Summary - DIAAMOND (Development of Non-destructive Inspection Approaches for Automatic detection and MONitoring of Damage evolution)

Executive Summary:
The aim of this project is to develop innovative Non-Destructive Testing (NDT) techniques to on-line monitor CFRP damages during structural tests execution. The demonstrator has included one NDT technique. NDT instrumentation performs automatically and hugely reducing human intervention. Data acquisition and analysis can be accessed through network in real-time.

Up to now, ultrasonic conventional manual inspection has been carried out. In that context, for safety reasons, facilities are stopped before. One of the first steps of the project has consisted of demonstrating the feasibility of novel NDT techniques. Among others, non-contact advanced ultrasonic inspection was proposed (laser ultrasonics, air-coupled UT) as well as other imaging techniques, such as infrared thermography and laser shearography. All these approaches were postulated with the aim of:
- avoiding/reducing human intervention
- reducing inspection time
- improving inspection quality by providing NDT data positioning and recording
- simplifying system automation, and
- providing processed data by means of image processing and data fusion, extracting
automatically relevant information to support structural test follow up and associated
decision making procedures.

A NDT demonstrator has been validated at subcomponent level (flat panels) and in a more realistic scenario (full scale cockpit mock-up).

Project Context and Objectives:
Below, an exhaustive description of objectives within the project context is presented, as well as the achievements during the project related with them.

TOTAL TEST TIME REDUCTION AND SAVING IN HOURS OF HUMAN PRESENCE (NDT TESTS COULD RUN IN THE EVENING OR WHENEVER THEY ARE REQUIRED):

The system developed allows monitoring even during a whole weekend, as validated during the validation tests.

POSSIBILITY OF A VERY EARLY DETECTION

During the project different monitoring tasks have been performed successfully during structural tests over different specimens. In all of them there have been registers of failures of the specimen of different nature before the final failure. One of the Consortium proposals for industrialization in the future is to introduce an alarm during the precise moment when the indication appears. Management of these alarms could be a big improvement and need a precise specification of needs.

NDT TECHNOLOGIES FOR COMPOSITES

There has been a huge amount of tests using different NDT techniques to inspect different composite specimens, in order to assess their pros and cons to be chosen for the implementation on the final system (around 172 inspections).

PRINCIPLE OF AUTOMATION: AUTOMATIC CONTROL OF SIGNAL AND SENSORS

The NDT system can be managed and controlled in a remote way, recording the data and being available through an IP network in a remote way.

PRINCIPLE OF AUTOMATION: AUTONOMOUS SCANNING AT CONCERNED AREAS

The NDT technique chosen to be integrated in the system is based on imaging, traditional scanning (as it is in UT NDT techniques) is avoided.

PRINCIPLE OF AUTOMATION: SCAN COMPARISON WITH REFERENCE

The system developed has a tool that compares NDT registers based on imaging. The tool allows to compare two different images that can correspond to different NDT methods.

PRINCIPLE OF AUTOMATION: RECORDING FUNCTIONALITY IN BUFFER STORAGE CAPACITY FOR AT LEAST 24 HOURS

An specific test during the Final Validation tests has been carried out consisting in monitoring during a whole weekend, and it has been successful.
It has to be remarked that after a proper assessment, it has been concluded that a Computer based device with the capabilities of real time processing and storing at the same time and in parallel would be out of the economic scope of the project.
In that sense, the possibility to store everything it is just dependable of the capabilities of a specific Workstation (it would be a matter of cost). Because of that, it has been validated the real-time monitoring, storing only the data corresponding to moments where relevant events have happened, and not storing all the information, but validating the real-time monitoring capability.

PRINCIPLE OF AUTOMATION: INTERFACE THROUGH STANDARD COMPUTER AND COMMERCIAL OPERATIVE SYSTEMS

This principle has been completely achieved, as the Server Side Software applications can be running 24 hours as a service. Any capable device, properly configured and with the Client Side applications installed, can access through an IP network to the services provided by the Server Side software.
All the software is running in standard computer and commercial operative systems.

PRINCIPLE OF AUTOMATION: PORTABILITY AND MANAGEMENT BY ONE PERSON

The management of the integrated system is completely possible by one single person, once installed. The system is portable, it could be moved to a second structure with the same dimensions than the first structure. It will take time and cost (if specific devices for the second structure are demanded). The mechanical system is more complex that initially required in the proposal, and makes the final inspection system able to perform automated movements. The system is more complex, with many different devices and subsystems embedded, so the portability is possible, but needed to be performed by several people.

APPLIED TO STRUCTURAL TESTING

This objective has been taken into account from the beginning of the project as one of the main objectives and as a prerequisite for the system to develop. It has been fully accomplished and validated during several tests.

ON LINE RESULTS TRANSMISSION: SERVICE-ORIENTED ARQUITECTURE (SOA) WILL BE USED IN ORDER TO TRANSMIT RESULTS ON REAL-TIME

The integrated solution developed during the project is based on a client-server configuration, having the possibility to control and manage the system from a capable Hardware device connected to the same IP network than all the Server Side of the System, properly configured. It is possible as well to visualize and perform evaluations of the data being recorded from this remote device.

Project Results:
DEFINITION OF A SUITABLE TECHNIQUE

During the first stage of the project, different NDT testing techniques were assessed, selecting the most suitable ones to be tested for the project targets. There was a deliverable intended for the purpose of presenting all the fundamentals of each technique, followed by different applications of them in the aerospace and other industrial sectors. The main advantages and constraints of each one were assessed as well.
The NDT techniques assessed as a first approach was as follows:
1. Infrarred Thermography (IRT)
2. Laser Shearography (LS)
3. Ultrasound (UT)
Conventional Ultrasound
Phased Array Ultrasound
4. Air Coupled Ultrasound (AUT)
5. Laser Ultrasound (LUS)
In the attached document are included some tables detailing the characteristics of the different NDT methods assessed, ponderating their performance, assessing their defects detectability, positioning, characterization and sizing capabilities as well.
After having a global vision of all the characteristics of the different techniques applicable to monitoring of structural test, some of them show a better combination of properties for industrialization of the monitoring process, having into account defects detectability, on-line and in-live measurements (inspection speed) and influence of environmental or test-related interference such as vibrations.

TRIALS WITH DIFFERENT NDT TECHNIQUES

Along with the previous theoretical assessment, based on the state of the art of different NDT techniques, there was an exhaustive tests battery over different small coupons making use of the most appropriate NDT techniques. The total amount of inspections was 172.
These inspections are summarized in a table included in the attached document.
In view of these results the conclusion is, for the material configurations and parts under study, that typical defects are detected in all cases by the majority of the methods. Air Coupled ultrasonics might be a little behint in detectability for some types of defects. Other techniques characteristics to take into account are the sensibility, applicability, cost and difficulty of set up preparation. They are summarized in a table included in the attached document.
According with the initial theoretical assessment and related to the obtained results from the different inspected parts, infrarred thermography complies with most of the detectability requirements. The technique is capable of identifying different types of indications like delaminations, macro voids, fibre gaps, lack of resin and induced damage, but limited for micro-porosity. On the other hand, the foreseen inspection system of the DiAAMond project is targeted to the monitoring and detection of damage evolution during mechanical testing. Micro-porosity is a consequence of the manufacturing process and analyzed previously by certified inspection protocols, and not appearing during static or fatigue testing, and its detection it is out of scope in the current project.
Other technologies such as ultrasonic methods and laser shearography depend more heavily on environmental conditions like vibrations during mechanical test. For this reason they are not the more convenient technique for monitoring operations.
Due to the possibility of performing easy inspection set-ups, the advantage of non-contact and reduced inspection times, infrared thermography makes possible the evaluation of large areas in very short processing times. Also this technique could perform live monitoring inspections in a wide range of materials configurations and structures like the available in the MT-1 cockpit demonstrator, as presented in this report, unfeasible for other NDT techniques under evaluation, and suitable for the detection of damage apparition and evaluation of its evolution. A wide variety of infrared cameras are available, and with different sensitivity to cost ratios. This last parameter can be adjusted for finding the most cost effective solution.

DESIGN AND DEVELOPMENT OF THE SYSTEM

In the attached document are included different diagrams that represents schematically the integrated system developed. As well are included different images and pictures that will explain in more detail all the subsystems presented below.

NDT SYSTEM

Acquisition Subsystem
The Acquisition Subsystem is based on a thermographic camera, specifically the model SC7600 of FLIR.

Excitation Subsystem
The Excitation Subsystem is based on two halogen lamps used to stimulate thermally the specimen to test.

SEMI AUTOMATED SYSTEM

Mechanical Subsystem
It consists of an arc-shaped support along the perimeter of half of the cross-section of the cockpit.

Control Subsystem
This system is based in a Workstation (PC) running all the processing and server side software needed and a specific Hardware element in charge of the automated movements of the Mechanical Subsystem. This HW element is called Siroco Lite, and is the one in charge of command to the mechanical subsystem to move to a determined position, being controlled by specific software running on the Workstation.
The workstation is running multiple softwares, dealing with:
Recorded frames processing
Specific Hardware responsible of the automated movements of the Mechanical Subsystem.
In this context, the HW element would become responsible of command to the mechanical subsystem to move to a determined position, being controlled by specific software running on the Workstation.
These two elements that form the Control Subsystem will be connected to each other through standard IP protocol, sharing a properly configured network. The connection will be performed through standard Gigabit Ethernet wiring and with the use of a Switch.
The software running in this Workstation will be in charge of the follosing algorithms:
For damage on-line monitoring (Passive Inspections). In charge of getting and recording the most relevant events during the monitoring.
For Active Thermography inspections, three algorithms are available to post-process the frames sequences acquired:
- First Derivative
- Second Derivative
- Residue
This Workstation running the processing and server side software applications will be connected as well with a standard USB cable to a module that is connected to a Power Source. This module will be lately the element activating/deactivating the Excitation Subsystem (lamps), controlled by the software running in the Workstation.

SirocoLite
This is the HW element that will be connected to the Mechanical Subsystem, and is in charge as well of their low level management, commanded by the server software running at the Workstation.

USER INTERFACE SYSTEM

The User Interface System is conceived as the set of elements modules and interfaces devoted to provide remotely required information in corresponding formats: video, pictures, graphics, text... of the elements being monitored.
It should account for specific software and hardware to carry out foreseen functionalities milking information being used remotely, also providing control commands into the different software modules of different subsystems to alter nominal monitoring procedures.
It will be the element in charge of running all the client side software, including all the user interfaces for remote operating the system, querying and evaluating data. The system should be based in all the software that is running from the client side. This software should be installed in a personal computer able to be connected to the same IP network than the Control Subsystem.The System should be located far from the area where the structural tests are performed, with the purpose of giving all the security measures to the human operator during the execution of the tests providing the operator the interface needed to schedule the tests and querying the results obtained.
Eventually for the final prototype, a personal computer should be used to run all these software and should be connected through wired Gigabit Ethernet connection to the Control Subsystem.
A wired connection will be more robust and free of interferences. Such connection should be based in a standard IP connection that can be implemented in a wireless flavor as well.
Multiple types of functionalities should be considered implemented in this module as inherent result of the accessibility to the core of Control Subsystem services:
- Parameters of inspection control
- Scale-up images to real size
- Inspection data
- Damage comparison functionalities
- Compilation of a damage/defect set of data

FINAL VALIDATION TESTS

At the last stage of the Project, the Final Demonstrator described above was installed and validated at Topic Manager facilities during structural tests over a full scale cockpit mock-up.
In the attached document are included some pictures where the Final Demonstrator is shown installed there.

SUMMARY OF FUNCTIONALITIES VALIDATION

At the attached document is included a table detailing the result of the final validation tests peformed along the development of the Preliminary Prototype and Final Demonstrator.

ENHANCEMENT FOR INDUSTRIALIZATION

Based on the final validation tests to check the functionalities of the Final Demonstrator and their limitations, an assessment for the improvement and industrialization of the system and technology has been performed.

Potential Impact:
SOCIO-ECONOMIC IMPACT

The following lines detail the expected impacts stated at Description of Work of the proposal, as well as the results achieved at the end of the Project.

Substitution of manual NDT inspection by an automatic process:

With the system developed, the Inspection process is launched and executed in a remote way, defining the parameters needed for the inspection and the time it will last.
The system provides the user to perform monitoring related inspections (during structural tests and in parallel with them) based on passive thermography, as well as scheduled inspections based in active thermography during stops of the structural tests.
Data storage optimization has been taken into account during the monitoring allowing to store only relevant information to the user.

Automated inspection with positioning recording:

The system is able to record and manage the acquired data. There are manual positioning tolos integrated in the system that allows the user to position in a manual way. The automation of this process can be carried out in a further stage of development in the future.
There are as well tolos to compare the NDT registers acquired with UT inspections with damage marked directly on the test article, in a qualitative way. More sophisticated tolos in this sense can be developed in the future in a further stage of development.

Test time reduction:

The test time can be reduced in a high degree by the use of the system developed.

Early damage detection by means of a larger number of NDT inspections and on-line access to processed data:

On line diagnosis is performed completely in automatic mode, giving to the user the possibility to analyze relevant data, because the system has embedded specific algorithms for filtering and lighting up data to be evaluated. The defect position and dimensioning are provided through different specific tolos developed and integrated in the final system. These tolos require user interaction to be performed completely. Other tools included in the software provide as well a comparison of NDT records. A complete set of software tools have been developed.
Tools to process NDT information (automatic evaluation) and decisión making tools will be taken into account for further and future developments, where a very precise specification about customer requirements and tolerances has to be provided in advance.

Dimensions of the monitored área versus resolution:

The Final Demonstrator includes a solution of compromiso in terms of mechanical devices to perform sensors displacements. This solution of compromiso has a high level of automation taking into account the Budget and the scope of the Project.
Recommendations to improve the automation of the system and different possibilities for industrialization of the system are included in a specific report.

Application to aircraft production programmes:

The system is perfectly able to be used in aircraft production programmes.

Application to other industries that make an intensive use of composite materials:

The system is perfectly able to be used in industries related with composite materials.

MAIN DISSEMINATION ACTIVITIES

Two papers describing the work performed in the project were presented at AEND conference (Spanish Asociation of Non Destructive Testing National Congress) and NDT for Aerospace 2015 , Germany (organized by the German Asociation of NDT). This international congresses oriented to the international NDT industry and scientific comunity, were held in Seville-Spain during May 2015 and in Bremen-Germany during November 2015, respectively. There were oral presentations as well showing the tasks described at the papers.

EXPLOITATION OF RESULTS

Also, CATEC and TECNATOM have been participating on several talks with current/future customers within the aerospace industry, where results on DiAAMond project have been introduced for further exploitation. There have been as well general difussion notes on the web (CATEC/TECNATOM diffusion general routes but also external).

List of Websites:
Public website address: N/A

Relevant Contact Details:

TECNATOM:
Esmeralda Cuevas (ecuevas@tecnatom.es)
Sergio Hernández Ruiz (shruiz@tecnatom.es)

CATEC:
Fernando Lasagni (flasagni@catec.aero)
Antidio Viguria (aviguria@catec.aero)