In order to get a deeper understanding of laser beam welding, a process model was developed at the Chair of Manufacturing Technology. It is based on the continuity equation, the equation of heat conduction and the NavierStokes equation. The model includes effects of Fresnel absorption, vapor pressure, surface tension, melting and evaporation enthalpy and energy loss due to evaporating material. This paper presents the results of a three-dimensional, transient finite volume simulation of a laser beam deep penetration welding process based on this model. The simulations show periodic keyhole oscillations and the complex fluid dynamics of the melt pool. A comparison of the evaporation rates calculated from the simulations and the experimentally observed process emissions shows good correlation. Furthermore, the simulations show pore formation at higher feed rates, the influence of a gap on the welding process and give an explanation for the welding behavior of zinc coated steel sheets.

No abstract

No abstract

No abstract

In this article, we present a technical description of a new type of anemometer for gas and especially liquid flows with high temporal and spatial resolution. The principle of the measurement is based on the atomic force microscope technique where microstructured cantilevers are used to detect extreme small forces. We demonstrate the working principle and the design of the sensor, as well as calibration measurements and initial measurements of turbulent flows, which were performed in air and water flows.