• Finite Element Predictions of Temperature Distributions in a Multipass Welded Piping Branch Junction

      Jiang, Wei; Yahiaoui, Kadda; Hall, Frank Richard (American Society of Mechanical Engineers (ASME), 2005)
      This contribution deals with the complex temperature profiles that are generated by the welding process in the intersection region of thick walled, cylinder-cylinder junctions. These affect material microstructure, mechanical properties and residual stresses. Knowledge of the thermal history and temperature distributions are thus critical in developing control schemes for acceptable residual stress distributions to improve in-service component behavior. A comprehensive study of three-dimensional temperature distributions in a stainless steel tee branch junction during a multipass welding process is presented. A newly developed partitioning technique has been used to mesh the complex intersection areas of the welded junction. Various phenomena associated with welding, such as temperature dependent material properties, heat loss by convection and latent heat have been taken into consideration. The temperature distribution at various times after deposition of certain passes and the thermal cycles at various locations are reported. The results obtained in this study will be used for on-going and future analysis of residual stress distributions. The meshing technique and modeling method can also be applied to other curved, multipass welds in complex structures.
    • Kinetic Monte Carlo approach to nonequilibrium bosonic systems

      Liew, T. C. H.; Flayac, H.; Poletti, D.; Savenko, I. G.; Laussy, Fabrice (American Physical Society, 2017-09-18)
      We consider the use of a kinetic Monte Carlo approach for the description of nonequilibrium bosonic systems, taking nonresonantly excited exciton-polariton condensates and bosonic cascade lasers as examples. In the former case, the considered approach allows the study of the cross-over between incoherent and coherent regimes, which represents the formation of a quasicondensate that forms purely from the action of energy relaxation processes rather than interactions between the condensing particles themselves. In the latter case, we show theoretically that a bosonic cascade can develop an output coherent state.