The joining of the titanium alloy Ti-6Al-4V by LFW is analysed by FE and analytic modelling, in both 2D and 3D. For the purposes of model validation and testing, experimental work is carried out using pilot-scale apparatus. Thermocouple wires were inserted in to several welds, to measure thermal values at varying locations. The sensitivity of the measured temperatures and upset rates to the critical process variables; amplitude, frequency and the applied pressure - are shown to be consistent with the predictions of the 2D and 3D modelling. The flash produced is found to be dependent upon the ratio of oscillation amplitude to applied load; when this is large a rippled morphology is produced. The 2D models replicated the flash formation behaviour well. Results for residual stress fields in three principal axes were calculated from the FE model, and compared to experimentally determined residual stress values. The modelled predictions were found to be reasonable. Further, a simple analytical model of the process is proposed, in which mechanical work is balanced against flash formation; at steady-state temperature is predicted to decrease exponentially with distance in the HAZ, and the temperature gradient in the HAZ is predicted to increase as the upset rate increases, as observed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:678890 |
| Date | January 2010 |
| Creators | Turner, Richard Paul |
| Publisher | University of Birmingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.bham.ac.uk//id/eprint/6451/ |
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