TWI Industrial Member Report Summary 905/2008
By W Xu and M F Gittos (TWI Ltd)
M Roe, M B Wood and M J Wilson (Bombardier Transportation Ltd)
Questions have been raised on crashworthiness of welded aluminium joints in rail vehicles as a result of recent highly publicised vehicle collision accidents in the UK and in Europe. In those accidents, the welded joints in 6000 series aluminium alloy extrusions exhibited low energy absorbing fast fractures. In recent years, TWI has been actively engaged in research aimed at a better understanding of such fractures.
Previous work has pointed out that strength reduction is unavoidable in welds produced by the currently established fusion and non-fusion welding processes in heat treatable aluminium alloys. Therefore, structural reinforcement should be considered in designing welded joints in aluminium structures to compensate for the weld strength undermatch. Weld over-sizing is being increasingly adopted by rail vehicle designers and manufacturers.
Tests of welded full-scale aluminium joints with or without weld over-sizing have been completed as a part of a European research project on crashworthiness of joints in aluminium rail vehicles. This test programme provided an opportunity to demonstrate and validate the performance of full-scale welded joints. This report provides a description, analysis and discussion of the performance of the full-scale aluminium joints in high-speed impact tests.
- Reproduce fast weld fractures similar to those observed in rail vehicle accidents.
- Demonstrate weld over-sizing as a mitigation method for weld fracture.