Browsing by Author "Russell, Michael J."

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    Energy and force analysis of linear friction welds in medium carbon steel
    (2010-08-31T00:00:00Z) Ofem, Usani Unoh; Colegrove, Paul A.; Addison, Adrian C.; Russell, Michael J.
    The linear friction welding process is rapidly developing into an important manufacturing technology for high quality joining of engineering materials. The energy required for linear friction welding is an important issue due to economic and environmental reasons, but is not currently fully understood. This paper describes a comprehensive evaluation of the energy input during linear friction welding of a medium carbon steel with different process parameters. This calculation is based on an analysis of force and displacement data from the machine, which takes momentum into account. The analysis shows that energy input to the weld is minimised with high frequencies and rubbing velocities; however, there is a considerable amount of energy lost in oscillating the machine tooling under these conditions. Furthermore, analysis of the force indicates that a peak load occurs just before the samples being aligned, which is probably caused by ploughing of the samples during welding.
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    Energy and force analysis of Ti-6Al-4V linear friction welds for computational modeling input and validation data
    (Springer, 2014-09-26) McAndrew, Anthony; Colegrove, Paul A.; Addison, Adrian C.; Flipo, Bertrand C. D.; Russell, Michael J.
    The linear friction welding (LFW) process is finding increasing use as a manufacturing technology for the production of titanium alloy Ti-6Al-4V aerospace components. Computational models give an insight into the process, however, there is limited experimental data that can be used for either modeling inputs or validation. To address this problem, a design of experiments approach was used to investigate the influence of the LFW process inputs on various outputs for experimental Ti-6Al-4V welds. The finite element analysis software DEFORM was also used in conjunction with the experimental findings to investigate the heating of the workpieces. Key findings showed that the average interface force and coefficient of friction during each phase of the process were insensitive to the rubbing velocity; the coefficient of friction was not coulombic and varied between 0.3 and 1.3 depending on the process conditions; and the interface of the workpieces reached a temperature of approximately approximately 1273 K (1000 °C) at the end of phase 1. This work has enabled a greater insight into the underlying process physics and will aid future modeling investigations.
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    Modelling of the workpiece geometry effects on Ti–6Al–4V linear friction welds
    (Elsevier, 2015-12-15) McAndrew, Anthony; Colegrove, Paul A.; Addison, Adrian C.; Flipo, Bertrand C. D.; Russell, Michael J.; Lee, Lucie Alexandra
    Linear friction welding (LFW) is a solid-state joining process that is finding increasing interest from industry for the fabrication of titanium alloy (Ti–6Al–4V) preforms. Currently, the effects of the workpiece geometry on the thermal fields, material flow and interface contaminant removal during processing are not fully understood. To address this problem, two-dimensional (2D) computational models were developed using the finite element analysis (FEA) software DEFORM and validated with experiments. A key finding was that the width of the workpieces in the direction of oscillation (in-plane width) had a much greater effect on the experimental weld outputs than the cross-sectional area. According to the validated models, a decrease of the in-plane width increased the burn-off rate whilst decreasing the interface temperature, TMAZ thickness and the burn-off required to remove the interface contaminants from the weld into the flash. Furthermore, the experimental weld interface consisted of a Widmanstätten microstructure, which became finer as the in-plane width was reduced. These findings have significant, practical benefits and may aid industrialisation of the LFW process.
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    Modelling the influence of the process inputs on the removal of surface contaminants from Ti-6Al-4V linear friction welds
    (Elsevier, 2014-11-03) McAndrew, Anthony; Colegrove, Paul A.; Addison, Adrian C.; Flipo, Bertrand C. D.; Russell, Michael J.
    The linear friction welding (LFW) process is finding increasing interest from industry for the fabrication of near-net-shape, titanium alloy Ti–6Al–4V, aerospace components. Currently, the removal of surface contaminants, such as oxides and foreign particles, from the weld interface into the flash is not fully understood. To address this problem, two-dimensional (2D) computational models were developed using the finite element analysis (FEA) software DEFORM and validated with experiments. The key findings showed that the welds made with higher applied forces required less burn-off to completely remove the surface contaminants from the interface into the flash; the interface temperature increased as the applied force was decreased or the rubbing velocity increased; and the boundary temperature between the rapid flash formation and negligible material flow was approximately 970 °C. An understanding of these phenomena is of particular interest for the industrialisation of near-net-shape titanium alloy aerospace components.