Analytics, materials technology and process diagnostics

The metallographic and materialographic analysis of samples and customer components is essential for the research carried out at the Department of Production Engineering. In addition to the preparation of a wide variety of materials, including aluminium alloys, steels, copper and polymers, further analyses are performed. Access to additional equipment, including scanning electron microscope, X-ray diffractometer or laser scanning microscope as well as other equipment is possible via the  Institute for Micro- and Nanotechnologies MacroNano®.

Various systems are available for contact and contactless temperature measurement, which allow conclusions to be drawn about the temperature-time profile during material processing. The time synchronization with other measurement signals, e.g. current-voltage curve in arc welding, the linkage with signals of the process emission in laser joining or the process forces and torques in friction stir welding allow an in-depth analysis of the process and material behaviour. 

The recording and evaluation of flow processes can be carried out using high-speed schlieren technology. The self-developed mobile test rig allows for maximum contrast at lowest density differences and can be used in different laboratories or on-site at partners' or customers' facilities. The setup allows the investigation to be carried out during the ongoing welding process, whereby the process emissions can be largely masked out.

The evaluation of deformations during mechanical testing allows the description of existing damage mechanisms as well as the localization of critical component areas. Corresponding investigations, especially by means of process diagnostics and metallography, allow the detailed description of the interrelations between process, material and mechanical properties. In addition to the use in materials testing, these systems, which also allow measurement on hot surfaces, can be used during joining and welding processes for quantifying distortion, determining local strain areas as well as material changes.

High-speed recordings enable the development of an advanced process understanding through the temporal resolution of the processes by observing it from the outside, e.g. with regard to spatter detachment during laser beam welding, droplet transfer and arc deflection during gas-shielded metal arc welding, solidification processes of the melting pool of materials susceptible to hot cracking, or tool behaviour during friction stir welding processes. Effects are quantified on the basis of software solutions developed in-house.

Spectral and acoustic process emissions are used for process monitoring and control, e.g. for the control of pulsed laser beam welding of aluminium-copper joints. The systems allow flexible recording of the process emissions as well as time synchronization with other measured signals. In addition to the existing systems of the Production Technology Group,  Fraunhofer IDMT and Fraunhofer IZFP are cooperating in the field of acoustic emissions.

On the one hand, the intensity distribution of the laser beam can be deliberately manipulated by optical elements. On the other hand, deviations, e.g. a focus shift, often occur in practice due to contamination or the effect of the thermal lens. The precise knowledge of the beam profile, the power distribution as well as the power densities is essential for consistent results. In addition to devices for caustic and power measurement of continuously operated beam sources, there is also the possibility of time-resolved power measurement of pulsed laser beam sources.