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WELDMINDT Résumé de rapport

Project ID: 323427
Financé au titre de: FP7-JTI
Pays: Spain

Final Report Summary - WELDMINDT (Open rotor Engine WELDed parts inspection using MINiaturizable NonDestructive Techniques)

Executive Summary:
During WELDMINDT project, the development as well as the capability of three novel non-destructive testing techniques (Active Thermography, Shearography and Laser Ultrasonics) was analysed. At the beginning of the project representative samples were manufactured which consisted of welds containing defects that resemble real conditions. The initial developments were assisted by Finite Element Modelling in order to better understand the underlying physical phenomena. As a result of extensive laboratory work for finding the best excitation and detection system some relevant conclusions were drawn. Laser Ultrasonics was found to be a very promising technique for surface defect detection, although its maturity is not as high as in the other techniques. With respect to Shearography, a novel procedure was suggested that allows inspecting thin plates from the back side (opposite side of defects location). This is really advantageous for hidden areas inspection since the miniaturization of the system is not required. Finally, an automated inspection system was build based on Active Thermography as a proof of concept of the benefits of this technique for the project goals. This was performed in a relevant environment and over representative samples (part of a turbine). In addition, a miniaturization concept was suggested and proved at a lab scale.

Project Context and Objectives:
Non Destructive Tests (NDTs) are necessary in order to inspect every single welded part, avoiding statistical approaches, in accordance to the “zero defects and zero failures” policy.

In addition, during aircraft engines life some factors (fatigue, stress, wear, extreme temperature changes, cycles …) can affect the integrity of different parts, being the rotating the most affected ones. Welded parts are subjected to high temperatures during welding process, and in most of the cases, melting temperature is achieved. The high temperature reached in the Heat Affected Zone (HAZ) modifies material properties and turns this area into a weak point of the component. Therefore, in order to ensure the engine life and flight safety, regular inspections of engine welded parts are crucial to detect weld defects (flaws, pores…).

The complexity of aircraft engines geometry has increased drastically. Future engine architectures, as Open Rotor engines, make the inspection access to certain parts difficult or even impossible with currently available inspection techniques. Taking this into account, WELDMINDT project dealt with the development of innovative NDTs, with capability of being:

- Miniaturized, allowing the access to previously inaccessible parts.
- Automated for industrial and in field applications.

Currently, traditional methods as Visual Inspection, Fluorescent Penetrant Inspection (FPI) and Radiography are being used for aero-engine welded parts testing. Due to the geometry complexity of Open Rotor Engines, the access to certain areas with these techniques is difficult or even impossible -as previously mentioned- and this leads to an inspection costs increase in manufacturing and maintenance, due to the need of dismantling the engine for inspection (when inspection is possible).
By the used of novel inspection methods -with automation and miniaturization possibilities- the following main outcomes were expected from WELDMINDT project:
a) An increase of at least 20 % in defect detection capability and sizing accuracy through the combination of multiple NDT techniques together with advanced signal processing.
b) Modify the aero-engine inspection time concept: from minutes-hours (or even days in maintenance) to seconds
c) Gain access/vision to currently inaccessible parts by means of non-contact NDTs.
From a technical point of view, the following technical objectives need to be mentioned:

a) Integration of a NDT system for welds inspection: shearography, Infrared Thermography and Ultrasonic inspection
b) Use laser as a single excitation source for the inspection system
c) Advance in the knowledge of pseudo-real defects generation in advanced materials with different welding processes
d) Develop a FEM based model valid for fast piece simulation
e) Develop an automatic inspection system based on industrial robotics applications
f) NDT System Miniaturization
g) Develop an “automatic” defect detection and sizing estimation software
h) Demonstrate the applicability of the designed system over real aero-engine welded parts.

Project Results:
Link to the abovementioned technical objectives, this section specifies the main tasks carried out during the whole project as well as the results achieved. This is reviewed by each technical objective:

a) Integration of a NDT system for welds inspection: Laser Ultrasonics, Infrared Active Thermography and Shearography,

For achieving this technical objective, each one of the NDT systems were developed individually before facing the integration into a single inspection system:

Laser Ultrasonics

A set-up was built capable of performing non-contact ultrasonic tests satisfactorily. Some welds were scanned and the obtained signal reconstructed leading to an image of the weld containing acoustic waves amplitude (see the following figure).
The relation between signal amplitude at different pulse peaks was also studied. As a result, the capability of detecting defects was proved. However, Shearography and Active Thermography were found to be more mature technologies for meeting project requirements.

Active Thermography
In Active Thermography a thermal excitation system was designed after a deep analysis of different techniques such as heat gun, flash lamps, halogens or laser. Most of the excitation systems were capable of revealing crack/defects as hot spots. However, the most important aspect is related to the interaction between thermal wave and defects. In the case of laser excitation, the local heating provided allows the subsequent analysis of this heat disturbance and also the scanning of long welds. A laser scanning system was designed for generating the heating of the samples. In this manner welds were scanned with enough power density to cause temperature peaks in cracks or defects.

In addition, the Active Thermograph based inspection system required some analysis of the resulting temperature fields. In this regard, great efforts were made to develop a method for defect detection which was based on the thermal footprint of a defect.

In order to assess system´s capability, samples were tested via conventional NDT techniques such as visual inspection, liquid penetrant or radiography in some cases. This procedure was useful in order to assess the reliability of the system. It was observed that the developed Active Thermography system may be a very suitable technique with potential to replace conventional techniques although further development and tests will be required to assess its reliability.


Shearography is an optical technique that is widely used in non-destructive testing of composite or non-metallic materials. Its principle is based on the disturbance in the shearography fringe pattern caused by a potential subsurface defect when the component is excited by a mechanical or thermal load. For non-metal components, both mechanical loading (e.g. vacuum pressure) and thermal heating can be used. However, when inspecting metallic components, only thermal heating is the practical excitation method. Since the thermal conductivity for metals is significantly high, shearography fringe pattern generated by thermal heating is highly transient. For the rapid changing fringe patterns, conventional technique including phase shift is difficult to implement. As a result, little applications of shearography for NDT of metal components have been reported.
The research work on shearography in this project was focused on developing a new procedure that can be used to detect subsurface defects within Inconel 718 sample components where existing conventional shearography techniques and procedures are unable to detect. The new procedure involved dynamic viewing of an animation of the shearography fringe patterns. Since human eyes are good at identifying tiny changes in a dynamic event, it is relatively easy to observe consistent disturbances that are related to the potential defects in the fringe patterns over a certain period of time of the video. Figure 3 shows the optical set-up for the shearography where a Michelson interferometer was used as the image shearing device, which allowed adjusting the image shearing amount to achieve the optimal shearography effect. Figure 4 shows a single fringe pattern extracted from a fringe video, where the weak signs of cracks are highlighted. These weak signs are more obvious when viewing the fringe video at certain period of time.

b) The development of the three NDT systems was accomplished in such a manner that the resulting capability met the project requirements in terms of the detectable defect size, automation possibility and miniaturization capability. This was performed satisfactorily. With regard to the integration of the three NDT systems, it was found that each system required its excitation features and therefore the combination could not be conducted (technical Objective b. Use laser as a single excitation source for the inspection system).

c) Advance in the knowledge of pseudo-real defects generation in advanced materials with different welding processes
Two different types of defects: natural -created during welding process- and artificial through a machining process (Electro Discharge Machining) were manufactured. Twenty-two plates were welded via different processes such as Laser Beam Welding and TIG welding. Samples were of rectangular shape and these were prepared so that they simulate real conditions. As a result of this task representative samples were obtained suitable for the development of novel inspection techniques.

d) Develop a FEM based model valid for fast simulation

In this regard, FEM simulations were launched for better understanding of the inspection concept phenomena. Two different models were prepared: mechanical model (Dynamic explicit analysis) and heat transfer model both of them over sane and cracked samples. In these simulations, the discontinuity caused by a given crack was assessed both in the thermal wave (heat flux) and the mechanical wave given a clear idea of the expected resulting signals.

e) Develop an automatic inspection system based on industrial robotics applications

The automation of the inspection system was only faced for the case of Active Thermography since this was the technology with the highest level of maturity to meet project requirements. In fact, as a proof of concept a robotized and automated system was built in University West facilities for proving system capability. The general scheme of the final inspection cell is presented in the following figure:

A 6-axis robot was used for the automation of the movement where the laser and IR camera were attached to the robotized arm according to the configuration developed at a lab level. For IR camera/laser/robot synchronization, a control was developed in LabView software which was also in charge of data acquisition and processing. Thanks to these software developments, the system provided results of the inspected part in a matter of few minutes, detecting automatically the defects. This proved that a shift in the current inspection concept (manual and long-lasting procedure) is possible fulfilling one of the main aims of the project.

f) NDT System Miniaturization

In the field of miniaturization, possibilities for reaching difficult to access areas were studied based on the project requirements provided by the Topic Manager. With regard to Active Thermography after a deep analysis a decision was made about the best configuration. The difficulties encountered were related to the thermal image acquisition and laser excitation into hidden areas. For that purpose, the use of mirrors was decided for achieving the established goals, and was demonstrated in a lab-setup.
With respect to Shearography, a miniaturization strategy was defined. Unlike Active Thermography, Shearography allows using commercial boroscopes as it is based on visual image acquisition. This makes the process of image acquisition of hidden areas easier.

g) Develop an “automatic” defect detection and sizing estimation software

An important step in order to fully automate the welds inspection consists of developing a signal interpretation tool in such a manner that it automatically detects the defective areas. Based on the developed image processing techniques a software was developed for that purpose capable of identifying defects (revealed as hot spots) including labelling and sizing. An example is illustrated in the following image:

h) Demonstrate the applicability of the designed system over real aero-engine welded parts.

The demonstration inspection procedure consisted on scanning the weld of the vane of an aeroengine, recording the thermal response of the surface after laser excitation and analysing the data to assess the quality of the weld: detection of defects and sizing. For that purpose, synchronization among robot, laser and IR camera was required as well as a processing algorithm. A control unit was developed in Labview software for data acquisition as well as synchronization between excitation laser and IR camera recording while the robot path was activated manually.

Potential Impact:
Potential impact and main dissemination activities and exploitation results

Although research projects like WELDMINDT are mainly focused on technical developments, it is also part of the work to identify exploitable foreground and present the results to a wider public, e.g. through conferences or fairs. Being a research work co-financed by the Clean sky Joint Undertaking (and therefore also indirectly by the European Commission), the results have to be used within European industries directly or later on.

WELDMINDT is a level 3 project, so it was working on advanced technology demonstration, specifically for the development of an innovative nondestructive technique for difficult to access engine parts. It was therefore expected to have developments matured to a Technology Readiness Level (TRL) between 4-5. After completing the WELDMINDT project and developing a proof of concept in a laboratory scale, it may stated that TRL 4 was achieved. In addition, the development was brought to a relevant scenario were the next steps and effors to increase its maturity level were established.

WELDMINDT dissemination activities may be summarized as follows:

. During the 1st period of the project the only dissemination activity performed was the uploading of the “Project fiche” (project description, information available in CORDIS) on LORTEK´s website. Both consortium and Topic Manager agreed that some dissemination activities should and must be carried out. The dissemination activities carried out in this period were:

- Oral presentation and article presented in three different scientific events: QIRT 2014, BiNDT2015, WCNDT2016 (to be presented)

- Press release in IK4-Lortek website

In addition a pending dissemination activity remains in the activities lists which needs to be discussed with the rest of the consortium:

- Publication in a peer-reviewed journal => At least one publication , to be published probably in the first half of 2016. Some scientific journals are already identified and are the following: Materials Science and Engineering A, Journal of Materials processing technology, Science and Technology of Advanced Material, Materials Today, Journal of Materials Science Research, among others. The last three are open access journals.

Related to exploitation of results, no patent application is planned at the moment, despite of having identified some key exploitable results.

Plan for Use and Dissemination of Foreground (hereinafter referred as PUDF, deliverable D6.3), submitted within 2. period report, identifies the dissemination and exploitation activities that may arise from the project. PUDF was made up of two sections:

* Section A, related to scientific publications generated thanks to the attained foreground: This section describes the dissemination measures, including any scientific publications relating to foreground. Its content will be made available in the public domain thus demonstrating the added-value and positive impact of the project on the European Union; and

* Section B, that contains exploitation plans: This section specifies the exploitable foreground and provides the plans for exploitation. All these data can be public or confidential; the report must clearly mark non-publishable (confidential) parts that will be treated as such by the European Commission. Information under Section B that is not marked as confidential will be made available in the public domain.

List of Websites:
Address of project public website and relevant contact details

There is no public website.

Relevant contact details:

Dr. (Mr.) Aitor García de la Yedra, Researcher of IK4-LORTEK, Smart Manufacturing Dpt., NDT and Monitoring Group


T: +34943882303

Dr. (Mr.) Erik Fernández, scientific in charge of the project

Researcher of IK4-LORTEK, Smart Manufacturing Dpt., NDT and Monitoring Group


Dr. (Mrs.) Anna Runnelmaln, Project Leader at UNIVERSITY WEST, Researcher of Department of Engineering Science

Assistant professor of Experimental Mechanics


Dr. (Mr.) Jianxin Gan, Project Leader at TWI

NDT Group, Principal Project Leader


Informations connexes


Josune Sarasola, (Financial Manager)
Tél.: +34 943 882 303
Fax: +34 943 884 345
Numéro d'enregistrement: 182046 / Dernière mise à jour le: 2016-05-17
Source d'information: SESAM