The feasibility of dissimilar friction stir welding(FSW)between the SAF 2507 super duplex stainless steel and the Incoloy825 Ni-based superalloy was evaluated.The microstructure and mechanical behavior of the weldment...The feasibility of dissimilar friction stir welding(FSW)between the SAF 2507 super duplex stainless steel and the Incoloy825 Ni-based superalloy was evaluated.The microstructure and mechanical behavior of the weldments were examined too.The results showed that the alloys were successfully welded together by positioning the SAF 2507 on the advancing side.The nuggets displayed higher hardness than the base metals,due to the occurrence of dynamic recrystallization and the subsequent refinement of the microstructures.The welded sample obtained the similar strength to the Incoloy 825 parent metal,showing the ductile fracture mode after the tensile tests by SEM.Moreover,the weld zone(31 J)exhibited higher and lower toughness than the Incoloy 825(23 J)and SAF 2507(42 J)parent metals,respectively.Based on the obtained results,the FSW method could be recommended to weld the super duplex stainless steel/Ni-based superalloy joints.展开更多
The present work aims to evaluate the increase in the number of spot welds in the 16 × 16 type fuel assembly structure that connects guide thimbles and spacer grids, in order to provide a proper joint for this co...The present work aims to evaluate the increase in the number of spot welds in the 16 × 16 type fuel assembly structure that connects guide thimbles and spacer grids, in order to provide a proper joint for this connection. This new and improved process can provide more stiffness to the whole structure, since the number of spots raised from four to eight. A 3-D geometric model of a guide thimble section was generated in a CAD （computer aided design） program （SolidWorks）. After that, the geometric model was imported to a CAE （computer aided engineering） program （ANSYS Mechanical APDL, Release 14.0）, where the finite element model was built, considering the guide thimble geometry assembled with the spacer grid through the welded connections. Boundaries conditions were implemented in the model in order to simulate the correct physical behavior due to the operation of the fuel assembly inside the reactor. The analysis covered specific loads and displacements acting on the entire structure. The method used to solve this finite element analysis was a linear static simulation in order to perform the connection between a spacer grid cell and a guide thimble section. Hence, four models was evaluated, differing on the spot weld number in the spacer grid and guide thimble connection. The rotational stiffness results of each model were compared. The results acquired from four and eight spot weld were validated with physical test results. The behavior of the structure under the acting force/displacement and the related results of the analysis, mainly the stiffness, were satisfied. The results of this analysis were used to prove that the increasing spot welds number is an improvement in the dimensional stability when submitted to loads and displacements required on the fuel assembly design. This analysis aid to get more information of extreme importance such as, the pursuance to develop better manufacturing process and to improve the fuel assembly performance due to the increasing of the bum-up.展开更多
文摘The feasibility of dissimilar friction stir welding(FSW)between the SAF 2507 super duplex stainless steel and the Incoloy825 Ni-based superalloy was evaluated.The microstructure and mechanical behavior of the weldments were examined too.The results showed that the alloys were successfully welded together by positioning the SAF 2507 on the advancing side.The nuggets displayed higher hardness than the base metals,due to the occurrence of dynamic recrystallization and the subsequent refinement of the microstructures.The welded sample obtained the similar strength to the Incoloy 825 parent metal,showing the ductile fracture mode after the tensile tests by SEM.Moreover,the weld zone(31 J)exhibited higher and lower toughness than the Incoloy 825(23 J)and SAF 2507(42 J)parent metals,respectively.Based on the obtained results,the FSW method could be recommended to weld the super duplex stainless steel/Ni-based superalloy joints.
文摘The present work aims to evaluate the increase in the number of spot welds in the 16 × 16 type fuel assembly structure that connects guide thimbles and spacer grids, in order to provide a proper joint for this connection. This new and improved process can provide more stiffness to the whole structure, since the number of spots raised from four to eight. A 3-D geometric model of a guide thimble section was generated in a CAD （computer aided design） program （SolidWorks）. After that, the geometric model was imported to a CAE （computer aided engineering） program （ANSYS Mechanical APDL, Release 14.0）, where the finite element model was built, considering the guide thimble geometry assembled with the spacer grid through the welded connections. Boundaries conditions were implemented in the model in order to simulate the correct physical behavior due to the operation of the fuel assembly inside the reactor. The analysis covered specific loads and displacements acting on the entire structure. The method used to solve this finite element analysis was a linear static simulation in order to perform the connection between a spacer grid cell and a guide thimble section. Hence, four models was evaluated, differing on the spot weld number in the spacer grid and guide thimble connection. The rotational stiffness results of each model were compared. The results acquired from four and eight spot weld were validated with physical test results. The behavior of the structure under the acting force/displacement and the related results of the analysis, mainly the stiffness, were satisfied. The results of this analysis were used to prove that the increasing spot welds number is an improvement in the dimensional stability when submitted to loads and displacements required on the fuel assembly design. This analysis aid to get more information of extreme importance such as, the pursuance to develop better manufacturing process and to improve the fuel assembly performance due to the increasing of the bum-up.
