Feasibility study on multifrequency excitation of the melt pool during ultrasonic-assisted laser beam welding.

The constantly increasing demands on components and their resource-efficient production require new strategies in modern process chains. The Collaborative Research Centre (CRC) 1153 "Tailored Forming" is working on the production of hybrid solid components made from joined semi-finished products with subsequent forming. Laser beam welding with ultrasonic assistance has proven to be advantageous in the production of semi-finished products due to the active influence on the microstructure as a result of the excitation. In this work, the feasibility of extending the monofrequency excitation of the melt pool used so far during welding to a multifrequency excitation is investigated. Results from simulations and experiments show that a multi-frequency excitation of the weld pool can be effectively realised. Furthermore, it is shown that a combination of previously separately used excitation methods (positioning of the melt pool in the vibration node and in the vibration antinode, respectively) with two different frequencies is successful and leads to a combination of effects as desired, what can be seen from micrographs.