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Research project (§ 26 & § 27)
Duration : 2021-12-01 - 2022-11-30

Monitoring the vibration properties of ultrasonic fatigue specimens during testing is a promising application of acoustic damage evaluation methods: As the longitudinal soundwave travelling through the specimen is disturbed and reflected on newly formed interfaces and discontunities (i.e. cracks), harmonic overtones of the nominal vibration signal at 20 kHz are generated. By monitoring the harmonic content of specimen vibration and comparing the current state over the course of a fatigue test to the virgin specimen, the progress of fatigue damage can be monitored in-situ in real time. The technique does not require the additional transducers typically employed in nonlinear acoustic analysis or direct optical observation of fatigue crack size in the specimens for fatigue crack growth analysis. Rather, the technique uses the available signal of specimen movement during high frequency resonance vibration. The project objective is the development of fatigue testing DAQ software to work in conjunction with prevously developed ultrasonic fatige testing equipment. This shall enable the in-situ realtime monitoring of fatigue damage in different metallic materials (e.g. cast steel, cast aluminium alloys) subjected to ultrasonic cycling. Suitable models shall be explored and further developed to asses the fatigue damage based on resonance frequency and harmonic overtone content, to detect - changes in vibration properties due strain localisations and/or initial short cracks at natural and artificially initiated stress concentrations - correlate the resonating properties (second or higher order harmonics, resonance frequency changes) with crack lengths in long cracks. - Additionally, the portion of crack initiation and the transition from initiation to propagation should be evaluated for very high-cycle fatigue failure.
Research project (§ 26 & § 27)
Duration : 2021-01-01 - 2022-09-30

Objective of the Project is the system-integrated and load dependent evaluation of the long-term reliability of high-speed turnouts, with focus on crack initiation and growth from the rail foot of moveable crossing points. The Project focuses on the development of a detailed understanding of the dynamics of the complete non-linear system comprising “wheelset – rail – slab track – soil”, capturing on one hand the influence of slab, concrete asphalt mortar and soil stiffness, and on the other hand the low-amplitude, high-cycle vibrations from wheel-rail contact on the loading of the switch rails. Ultimately, the cornerstones for an integrated maintenance concept for high-speed crossings should be provided. The Present Project itself is part of the jointly defined Research Programme of the COMET K2 Center on “Integrated Computational Material, Process and Product Engineering (IC-MPPE)” and supports reaching the goals defined in this Research Programme. The contribution by BOKU-IPM is to characterise the properties of R260 steel under cyclic loading in the very high cycle fatigue regime.
Research project (§ 26 & § 27)
Duration : 2020-09-01 - 2023-08-31

Spider silk (SPSI) has been established as one of nature’s most fascinating materials due to its unique properties. A remarkable application of the SPSI is its use in reconstructive medicine as nerve guidance structure/filament for nerve regeneration. The Schwann cells (SCs), which are a crucial part of the nerve regeneration process adhere to SPSI and migrate along it to support axonal elongation. SPSI degrades without inflammatory response or physiological pH changes. However, the interaction between the SCs and the silk and by that the SPSI properties, that promote SC adhesion are still unclear. The aim of this project is to elucidate material properties of SPSI, that are crucial for its unique performance in nerve regeneration. Not all spider silks show the same medical success, and we believe that properties such as composition, ultrastructure, and mechanical behavior have a pronounced influence on the acceptance of SPSI by SCs. Therefore, by combining experiments consisting of in vitro studies and the material characterization of various SPSIs, the properties, which are responsible for the advanced success of SPSI in nerve regeneration, will be clarified.

Supervised Theses and Dissertations