High frequency testing machine with climate chamber

• Subject Area: Mechanics and Constructive Mechanical Engineering
• Term: Funded in 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 441960148

Through the requested high frequency testing system with a climatic chamber, new scientific fields with new methods regarding e.g. very high cycle fatigue (VHCF), structural durability, the determination of fatigue crack growth thresholds or variable amplitude loadings in the threshold regime will be opened. From technical point of view, the high-frequency testing system closes the gap between the Structural Mechanics Institute's ultrasonic and servo hydraulic testing systems and will be specifically used in research projects, where both high test loads and high test frequencies are required. In the VHCF regime, crack initiation will be investigated using additively manufactured specimen, in which artefacts by means of artificial defects or cavities are printed during the manufacturing process. In order to investigate the size effect, the artefacts will be varied in position and size as well as the specimen will be loaded with bending and torsion with different mean stresses. Therefore, larger specimen and higher frequencies are necessary. Furthermore, fatigue test e.g. with additively manufactured functionally graded porous structures or component like specimen of medical applications will be performed. Due to different influencing factors, the variety of variables as well as higher limit number of cycles will be investigated, which is only feasible with high frequencies and therewith short testing time. Also a high number of basic fatigue experiments are necessary in the field of structural durability for the description of the residual strength or residual stiffness approaches, e.g. for composite structures, which consider different stress levels and stress ratios as well as load directions. Of especial interest are not only constant amplitude loadings, but also service loads in the context of both structural durability and fatigue crack growth in the threshold regime. In the field of structural durability, manipulations of the load spectrum, like omission and truncation, need investigations with high number of load cycles. In the field of the determination of the fatigue crack growth thresholds under Mode I and particularly Mixed Mode, new techniques are tested with block by block high number of load cycles. In practice, numerous components, e.g. pipelines, ship structures, wheelset axles or rotor shafts of windturbines, are exposed different temperatures beneath the freezing point. While the influence of low temperature on the fracture toughness is well-known, fatigue crack growth in the threshold regime as well as the appropriate mechanisms are rarely investigated.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Hochfrequenzpulsator
• Instrumentation Group: 2910 Dynamische Prüfmaschinen und -anlagen, Pulser
• Applicant Institution: Universität Rostock
• Leader: Professorin Dr.-Ing. Manuela Sander