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Content archived on 2024-06-10

Development of innovative tools and technique of high frequency (25 - 50 MHz) ultrasonic testing of laser , micro-arc, electron beam welding of thin walled welded constructions (thickness 0.5 - 5 mm) used in aerospace industry


Foreseen Results

Implementation of this project will allow :

to extend application field of ultra-sound method in order to control thin walled welded seams (thickness 0.5 - 5 mm) produced by laser, electron beam and micro-arc welding;
to increase control sensibility in 2 - 5 times and resolution in 3 - 8 times, that will make possible to carry out "on line" control of the parameters of molten pool during welding;
to carry out defects recognizing by several special methods
to economize silver contained materials due to reducing of radiography control.
Main features of the units of aerospace industry are the small thickness of used materials (0.5 - 5 mm) and elevated requirements to quality and to reliability of the welded joints. It is necessary to reveal pores with diameter 0.2 - 0.3 mm at resolution of testing 2 - 3 mm and also dangerous defects as lack of fusion and cracks.
Now, radiography is most commonly used for non-destructive testing of thin walled welded seams in aerospace industry, because the production-type ultrasonic equipment with frequencies range 1 - 5 MHz does not provide the required resolution. However, radiography has several serious problem : deficient reliability of some dangerous defects revealing, like, for example, lack of fusion, slots and cracks if their orientation does not coincide with direction of X-rays (that happens frequently); high labor requirements and low productivity; large expenses of silver contained materials (X-ray films).
More promising method of non-destructive testing is now considered to be one based on ultrasonic. The last five years large efforts were spent to develop advantage methods of ultrasonic testing. The main goal of these efforts was to enlarge the range of work frequencies of ultrasound up to 50 MHz in order to increase the axial and lateral resolution to find defects like porosity, delaminations, lack of fusion and cracks.

Thus, the main goals of this project are :

to enlarge the field of ultrasonic testing applications for detection and characterization of defects like pores, lack of fusion and cracks taking place in thin walled welded panels (thickness 0.5 - 5 mm) used at manufacturing of aircraft constructions
to develop special techniques of ultrasonic testing for "on line" control of welding

To reach the goals, it is necessary to solve the following complicated technical and mathematical problems :

to develop special high frequencies (20-50 MHz) ultra-sound transducers that will permit to obtain short periods (0.1ms) of elastic oscillations and to reach axial and lateral resolution of ultrasonic testing;
to develop special mathematical methods of digital treatment of ultra sound data (based on deconvolution, Fourrier's and Radon's transformations, etc) to increase control resolution;
to develop special technique of post welding defect diagnostic of thin walled welded joints and, also, "on line" monitoring of the volume of molten pool during welding

Call for proposal

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Avenue Guy de Collongue 36
69131 Ecully

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Participants (5)