In response to the need for an effective in-process quality assurance inspection method for friction stir welding (FSW), the SignaStir project has developed a unique and holistic system which detects critical defects in welds. This will enhance the confidence in FSW components and reduce the possibility of defective products being supplied to customers.
Friction stir welding is used in a variety of industries from shipbuilding to aerospace manufacturing and is best suited to mass production where repetitive long lengths of weld are produced quickly and in a cost effective manner. A previously limiting factor to the performance of the automated machinery that performs FSW and subsequently in its take-up was the lack of an effective in-process quality assurance method. As some of the defects are not visible on the weld surface it was vital for a holistic inspection system to be developed. This also increases the efficiency of FSW as it enables targeted component re-work and reduces wastage due to the ability to locate the potential flaws within a structure.
The SignaStir project evaluated the inspection capability of laser ultrasound in its application to FSW before developing an integration strategy that allows the monitoring system to be incorporated into new-build FSW equipment. The project was dedicated to the design and building of an integrated optical head, and the conception of user-friendly inspection software. Adaptations are also available to enable the SignaStir system provide automatic corrections to the welding machine settings. The project has also provided a new understanding of the application of non-contact inspection systems for the inspection of FSWs and the definition of the capability of non-contact inspection systems for inspection of FSWs.
A first test showed that installation of the inspection equipment on a large gantry production welding machine at SAPA had no impact on the operation of the welding machine. Good quality linear welds and linear welds containing intentional defects were produced. Final laboratory measurements on the linear weld produced during the demonstration have verified that the SignaStir system is able to detect the size of voids of interest to FSW users.
Research leading to these results has received funding from the European Union's Seventh Framework Programme managed by REA - Research Executive Agency http://ec.europa.eu/research/rea [FP7/2007-2013] under grant agreement number: 262150.
The SignaStir project partnership comprises: TWI, KIMAB, ISPL, Inspectahire, BCT, Rubitech, HBS Engineering and Sapa. Contacts:
For general enquiries regarding the SignaStir project please contact Dr Kathryn Beamish, firstname.lastname@example.org at TWI Ltd, Granta Park, Great Abington, Cambridge, CB21 6AL, UK. Tel: +44 (0)1223 899000, Website: www.twi.co.uk
All enquiries regarding the SignaStir inspection system should be addressed to Dr Henrik Schmidt, email@example.com at HBS Engineering, HBS Engineering ApS, Erdalsvej 1, 2600 Glostrup, Denmark. Tel: +45 21766440, Website: www.hbse.dk or www.signastir.com.