TWI

With regard to the dependence of shoulder friction generation in bobbin friction stir welding on the interference (compression) between the substrate and the tool, an investigation was undertaken into the effects of different interference (compression ratios) on tool dynamic behaviour, temperature and welded joint quality for AA 6082-T6 aluminium alloy substrates (thickness 4 mm) set in a butt joint configuration. To assess compression effects, three tools with different shoulder gap were fabricated. Welding trials were conducted using a manual milling machine at a spindle speed of 650 rpm and a travel speed of 60 mm/min. Process responses based on force and temperature measurements were recorded during welding. A theory based on empirical data was developed to describe shoulder interference effects and a slip-stick mechanism was put forward in terms of the dynamic interaction between an elastic tool and a viscoplastic substrate. The proposed causal relationships are discussed using a systems engineering approach.

10th International Symposium, 20-22 May 2014, Session 5A: Variants, Paper 03