Browsing by Author "Wen, S. W."

Now showing 1 - 3 of 3
  • Thumbnail Image
    ItemOpen Access
    Measurement and modelling of the transient thermal-mechanical strain field during GMA welding
    (2011-04-07T00:00:00Z) Coules, Harry E.; Cozzolino, Luis D.; Colegrove, Paul A.; Wen, S. W.; F, Vollersten
    The state of residual stress in welded joints is a well-studied topic, and many methodsof residual stress measurement are now available. However, far less is known aboutthe transient strains which occur during the welding process, even though these are thedirect cause of residual stresses. Efforts to model welding processes usually includetransient stresses and strains among their results, but in general these models can onlybe easily compared against experimentally measured residual stresses: there is a lackof published data covering strain in the transient regime.In this study, electrical resistance strain gauges were used to measure transient strainsduring welding, and comparison is made between these measurements and the resultsfrom a sequential thermo-mechanical finite element model of the process. Well-definedmechanical boundary conditions were used for the experiments to ease interpretationof the measured strain data, and to enable close approximation with the boundaryconditions of the computational model. The transient biaxial state of strain wasmeasured during Gas Metal Arc Welding (GMAW) of S355 steel samples in a bead-onplateconfiguration. Measured transient strains were found to be consistent betweensamples, and showed good agreement with the modelling results. It is hoped thatfuture study of welding transient strains will aid in the optimisation of in-processmethods to reduce residual stress, such as rolling and quench cooling.
  • Thumbnail Image
    ItemOpen Access
    Modelling distortion reduction on pre- and post-weld rolled gas metal arc welded plates
    (2011-04-07T00:00:00Z) Cozzolino, Luis D.; Coules, Harry E.; Colegrove, Paul A.; Wen, S. W.; F, Vollersten
    Residual stress generated during welding can cause distortion, especially when appliedon relatively thin plates. There are several standard and well documented techniquesto reduce distortion and residual stress after welding, however these techniques areoften costly and time consuming to implement on an industrial scale. In this paper wedemonstrate the pre- and post-weld rolling techniques for reducing weld distortion. Pre-Weld Rolling (PWR) can be applied before fabrication, potentially by the steelmanufacturer. An experimental investigation indicated that there was an average 38%reduction of distortion with this technique. Finite element analysis (FEA) was used todetermine the stress distribution to understand the phenomenon.
  • Thumbnail Image
    ItemOpen Access
    Rolling to control residual stress and distortion in friction stir welds
    (2010-08-31T00:00:00Z) Wen, S. W.; Colegrove, Paul A.; Williams, Stewart W.; Morgan, S. A.; Wescott, A.; Poad, M.
    Considerable residual stress and distortion can be produced by friction stir welding, impeding industrial implementation. Finite element analysis has been used to develop three innovative rolling methods that reduce residual stress and distortion in friction stir welds. Of the three methods, post-weld direct rolling where a single roller is applied to roll the top surface of the weld after the weld metal has cooled to room temperature proved the most effective. The residual stress predictions from the model compared favourably with residual stress measurements reported in an accompanying paper. Finally, the effectiveness of using post-weld direct rolling is illustrated with an industrial example of a large integrally stiffened panel, where the distortion was virtually eliminated.