Untersuchungen zur Prozessstabilität beim Laserstrahlgenerieren filigraner Stegstrukturen mit hohem Aspektverhältnis
Final Report Abstract
The results of the present investigation can be used in the industrial process of LASER welding with the goal to get a so-called ‘rib’ shape of the joint. Due to the squeezing effect of the Lorentz forces the resulting joint shapes into the desired quasi-rectangular cross-section with straight sides. The top of joint remains round because of the strong influence surface forces so far as the curvature of the drop considerably increases in this region. Furthermore, the cross-sectional shape of the joint strongly depends on the spatial distribution of the applied magnetic field and, consequently, on the shape of inductor. For example, for an inductor with rectangular cross-section, the maximum of magnetic field is situated in the middle point of the space between the side elements of inductor. As a result the liquid metal drop (melting pool) is squeezed primarily in its top part and compressed to the substrate. This configuration of inductor is not optimal in order to get a vertically stretched joint. With the triangular configuration of inductor the required for industrial application large values of aspect ratio of the resulting drop are available. In the experiment performed for the frequency 150 kHz and magnetic Bond number Bom = 17 the relationship A = 2.6 between the vertical and horizontal dimensions is obtained. The numerical model predicts a value A = 6.2 for the frequency 300 kHz and Bom = 60. The electromagnetic force is primarily concentrated in the lateral parts of the drop and squeezes it in horizontal direction. The top of the drop is not affected considerably by the Lorentz force and maintains a round configuration defined by the surface tension.
Publications
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Shaping of a liquid metal drop by means of a high frequency magnetic field, oral presentation at UKMHD 2008 meeting, University of Salford, June 2008, Salford, United Kingdom
O. Andreev, A. Pothérat, A. Thess
