Community Research and Development Information Service - CORDIS

Advanced welding for closed structures; AWCS

This research had the main strategic aim of contributing to the recovery of the competitiveness of the European shipbuilding industry, with regard to Far East countries by the development of a new production technology, based on stake welding, for the construction of closed steel structures. This methodology consists in the welding from the outside of the reinforcements of closed structures to the covering sheet. This technology has also the potentiality to be beneficial to several other industries involved in the production of metal works, like heavy duty cranes, that was a second application field directly covered by the project, trains and civil engineering steel works.

The advantages offered- and confirmed by the project - by the realisation of closed structures by stake welding, according to the use of the new proposed technology, and applied on specially designed structures, include:

-Enhanced product quality in terms of lightness and structural stiffness.
-Cost reduction, related to manpower.
-Improved social impact of the work, by reduction/exclusion of human intervention inside the structures, where a complex, difficult and potentially unsafe environment was met.

In order to achieve the objectives, several research actions were planned and performed:

-Definition of small scale samples, welding tests by Laser Stake process, testing of a range of gap values.
-Strength tests and metallurgical investigation applied to small-scale welded samples. The tests and analysis carried out were widely complete in order to clarify the behaviour of the laser stake welded material.
-A welding parameter database was developed and recorded in a CD-Rom.
-Definition of full scale samples, representing significant parts of ship hull and crane structure. Laser Stake welding of them. A comparison with traditional welded structures was also performed. Fatigue tests were carried out on the samples for the assessment of stake welded structural behaviour.
-Analysis of various technologies to detect the right position of hidden reinforcement plate for the sensing system. Experiments on thermograph, ultrasound and magnetic techniques were carried out before the definitive choice.
-Design and realisation of the final prototype of Sensing Head, development of the interface unit with laser plant controller.
-On line functional tests of sensing system in welding environment. The tests demonstrated that the accuracy of the sensing system did not prove to be suitable for leading the laser torch for a quality stake welding.
-Validation of project activities and definition of guidelines for stake welding application.
-Validation of the welding tests and the sensing system functionality.
-Guidelines definition for future applications of laser stake welding process.
-Guidelines definition for design of stake welded structures.

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Passeggio S. Andrea, 6
34123 Trieste
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