Enhancement of understanding about electron beam deep welding processes by making use of real-time - Polarisation intensity quotient goniometry of the vapour capillary with a special view to functional connections of the weld pool dynamics

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As in laser beam welding, process instabilities which are to be ascribed to the molten pool dynamics may also occur in electron beam welding. For the increase of the EBW process windows, a deeper understanding of the fluid-dynamic processes around the vapour capillary are required and, on the other hand, also measurement methods for the monitoring of the process-stability in real-time. The latter serves for fundamentals-oriented investigations and also for the quality monitoring in practical application. Within the framework of this project it is planned to use a novel polarisation goniometer which allows the determination of the slopes of observed surfaces and, thus, particularly the 3D monitoring of the capillary geometry with very high temporal resolution. The correlation with the geometry of current measurement, as they are common in EBW, and also the self-illumination of the capillary (X-ray radiation) shall contribute towards a better interpretation of these current measurements. This will serve for the enhancement of the analytical process model of the molten pool dynamics and its interdependence with defined beam parameters, based upon the gained measuring results about the temporal change of the vapour capillary in three spatial dimensions, particularly for capillary depths > 5 mm. Subordinate targets:Quantitative measurement of the capillary geometry at a high scanning rate.Correlation/Calibration of the calculated three-dimensional capillary geometry by synchronous measurement of the X-Ray self-illumination of the capillary. Determination of the limits of the measuring method. Differentiation between geometrical limits, such as the capillary inclination angle and the maximum resolution in the direction of the capillary bottom and also of a possible measurement restriction by the increasing self-illumation of the metal vapour plasma with increasing plate thickness. Representation of the qualitative temperature curve over the molten surface by using the position- and angle information of the mainly temperature-independent quotient image and the intensity distributions in the p- and/or s-polarised images. Determination of the specific natural frequency of the molten pool and also of superimposed beats by local molten waves dependent on the primary weld parameters. Measurement of the influence of a defined excitation of the molten pool oscillation by beam oscillation. Determination of the influence of defined beam geometries which vary from the ideal round beam, on the molten pool dynamics.