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Internal flow behaviour and microstructural evolution of the bobbin-FSW welds: thermomechanical comparison between 1xxx and 3xxx aluminium grades

Tamadon Abbas, Pons Dirk J., Sued Kamil, Clucas Don

Advances in Materials Science

2021

Vol. 21, nr 2(68)

40--64

The influences of processing parameters and tool feature on the microstructure of AA1100 and AA3003 aluminium alloys were investigated using bobbin friction stir welding (BFSW). The research includes flow visualization and microstructural evolution of the weld texture using the metallographic measurement method. Results indicated that the operational parameters of the welding (e.g. feed rate, rotating speed) and the geometry of the tool can directly affect the flow patterns of the weld structure. The microscopic details revealed by the optical and electron microscope imply the dynamic recrystallization including grain refinement and precipitation mechanisms within the stirring zone of the weld region. The microscopic observations for the weld samples show a better performance of the fully-featured tool (tri-flat threaded pin and scrolled shoulders) compared to the simple tool without inscribed surface features. The fully-featured tool resulted in a more uniform thermomechanical plastic deformation within the weld structure along with the precipitation hardening and the homogeneity of the microstructure.

Visualisation research of the flow processes in the outlet chamber–outlet bridge–inlet chamber zone of the gear pumps

Stryczek J., Antoniak P., Jakhno O., Kostyuk D., Kryuchkov A., Belov G., Rodionov L.

Archives of Civil and Mechanical Engineering

2015

Vol. 15, no. 1

95--108

This paper is a presentation of the theoretical analysis and visual experimental investigation on flow processes in the inlet chamber, outlet bridge and inlet chamber of the gear pump, commonly known as the trapped volume. In order to achieve that, the size and location of the considered chambers and bridge were determined, and next, the theoretical analysis was carried out. In order to verify the theoretical consideration, an experimental gear pump with transparent (plexi) bodies was designed and built. The pump was tested on a dedicated test stand. The visualisation research conducted for different values of the operational parameters (inlet pressure, temperature, rotational speed) proved the previously carried out theoretical analysis to be correct and, simultaneously, showed that there are areas in the gear pump where the flow processes are seriously disturbed. In order to eliminate the disadvantageous phenomena and processes observed in the pump, a new type of relief grooves was added to the design of the considered area (the solution was developed originally by the authors of this paper), which was consequently theoretically and experimentally examined. The results of both types of the research proved definitely that the application of the relief grooves resulted in a considerable reduction of the negative phenomena and processes in the considered area of the gear pump.

Badanie przepływów wewnętrznych w pompach pod kątem obliczania sił hydraulicznych

Karaśkiewicz K.

Prace Naukowe Politechniki Warszawskiej. Mechanika

2013

z. 261

3--142

Hydraulic forces occurring in rotodynamic pumps, especially those in power industry where they are essential in ensuring reliable pump performance, are important for appropriate sizing of shaft and bearings, proper designing the balancing device and avoiding the excessive pump vibration. Accuracy of the prediction of the forces is still not satisfactory. The reasons of and methods for predicting stable and unstable axial and radial thrust are comprehensively discussed. Three kinds of the pressure distribution assessment in the impeller sidewall gaps to get axial thrust are analyzed i.e. empirical, integral and RANS. Empirical and numerical investigations are presented. Additional issues important for predicting axial thrust are thoroughly analyzed such as impeller and balancing device annular seals flows, similarity laws for axial thrust, impeller internal force, forces in open and semi-open impellers. The issues of balancing axial thrust are also analyzed. The results of measurements and predictions of radial thrust in a single volute centrifugal pump are presented and methods of balancing discussed. The dynamic forces in annular seals are discussed. Unsteady interaction between impeller and diffuser and rotating stall are analyzed.