Ultrasonic welding is a suitable solid-state joining technique for producing high strength joints of similar or dissimilar materials, even of material combinations that were previously considered as not weldable. Different possibilities of transmitting the ultrasound into the joining partners exist whereas the investigated torsional welding principle utilizes a ring shaped sonotrode for transmitting ultrasonic vibrations tangentially to the welding force. Due to the specific sonotrode geometry ultrasonic torsional welding is a remarkably gentle welding technique, allowing to join even most sensitive components e.g. sensors or brittle elements. Nevertheless, ultrasonic torsional welded joints show high tensile strengths and helium-tightness.
Current investigations focus on the realization of metal/glass ceramics joints. In this project two metals with different thermal expansion coefficients have been utilized as the metal joining partner. The glass joining partner was the commercially available Li2O-Al2O3-SiO2 CERAN. For examining the microstructure light as well as scanning electron and transmission electron microscopy have been performed. Furthermore, residual stresses have been analyzed via X-ray diffractometry. Mechanical characterization has been carried out through shear as well as pull-off tests. Additionally, the clamping performance of the joining partners has been evaluated with in-situ laser vibrometry.