Highfrequency resonance fatigue testing system with a loading frequency of 1000 Hz

• Subject Area: Materials Engineering
• Term: Funded in 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 555176142

The high-frequency resonance testing system shall be applied in the CRC/TRR 375 for research into the fatigue behavior of additively manufactured (AM), hybrid-porous (HyPo-) materials. Key features of these materials are gradients in their chemical composition and/or porosity which are prerequisite for the general concept of the CRC/TRR 375 to “use the right material at the right place” in the design of technical components which undergo complex mechanical loadings. Due to the grading, the volume of HyPo-materials contain locally varying alloy compositions and/or porosities which strongly influence the local mechanical properties. Especially the fatigue behavior of HyPo-materials is by far not sufficiently investigated yet. The requested testing system will be used with 100% of his capacity in the subprojects C01 and C04 of the CRC/TRR 375. Both projects aim at closing the abovementioned research gap. Regarding the according fatigue tests, the following experimental challenges must be tackled: (i) The fatigue behavior of graded and/or porous material systems not only depends on the material gradient itself, but also on its orientation with respect to the loading direction. – Hence, a big number of fatigue tests is needed for comprehensive characterization. (ii) Especially in the High-Cycle-Fatigue- (HCF-) and Very-High-Cycle-Fatigue- (VHCF-) regime, the fatigue failure of HyPo-materials will be dominated by stress concentrations implied by characteristic microstructural notches occurring in AM materials and/or the morphology of the porous structures. – This implies a large scatter in the fatigue strength which again results in a large number of fatigue tests needed for statistical validation. (iii) The gradients and/or porosity result in highly inhomogeneous stress- und strain distributions even in case of uniaxial external loadings applied to HyPo-materials. – Hence, knowledge of the global and local stress-strain relationships is essential for the reliable design of HyPo-components. (iv) The graded porosity of HyPo-materials allows for an optimization of their damping properties, which may change during cyclic loading. This needs to be investigated as an important aspect of the envisaged multifunctionality of HyPo-components. Since servohydraulic fatigue testing systems don’t allow damping analyzes, this methodology is not viable for the planned research. (v) To cope with the extent of the HCF- and VHCF-experiments needed in the CRC/TRR375, an effective testing frequency of 1000 Hz is mandatory. – To achieve this requirement, the usage of ultrasonic fatigue testing systems which are established in VHCF loading of homogeneous materials is not viable due to the locally different mechanical properties of HyPo-materials. Hence, the requested resonance testing system is the only viable means to solve the research questions outlined above. The acquisition of this testing system has been strongly supported by the review panel of the CRC/TRR 375.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Hochfrequenz-Resonanzprüfsystem mit Beanspruchungsfrequenz 1000 Hz
• Instrumentation Group: 2910 Dynamische Prüfmaschinen und -anlagen, Pulser
• Applicant Institution: Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau
• Leader: Professor Dr.-Ing. Tilmann Beck