TWI Technology Briefing 830/2005
By S D Smith
Friction Stir Welding (FSW) has gained substantial interest in a wide range of industries, and is now the preferred choice of welding for many applications. There has been a large amount of experimental research to support the use of FSW,(1) but there are a number of issues that cannot easily be resolved through experimental testing. For example, FSW defects probably arise when there has been insufficient material movement during welding. It would therefore be of use to determine how material moves during welding. Experimentally this could be revealed through the use of markers placed on the weld line before welding. Markers have only revealed the final location of material movement after welding, and have not yet revealed how the markers move during welding. TWI is developing modelling methods for the analysis of FSW that might be used to answer this and other questions, and hence provide a complimentary method for the investigation of FSW.
TWI first investigated modelling of FSW through collaboration with Cambridge University. The UK Department of Trade and Industry (DTI) supported the Postgraduate Training Partnership (PTP) scheme. The PTP scheme allowed students to undertake doctoral studies at Cambridge University with relevant industrial input to their work from TWI. The first student completed his PTP PhD research on modelling of FSW heat flow in 2000. Two more PTP students and a Core Research Project (CRP) started work on modelling of FSW in 2000.
The PTP and CRP studies were conducted in parallel with a European Collaborative project (Join DMC) in which TWI collaborated with Cambridge University to investigate dissimilar material welds. The collaborative project developed detailed test results that are being used to validate the PTP and CRP models being developed.
This report summarises the full range of FSW modelling activities undertaken by TWI to provide TWI members with a complete overview in a single report.
The objective of this report is to provide a summary of the FSW modelling activities that have been undertaken by TWI.