High-rate dynamic testing maschine

• Subject Area: Mechanics and Constructive Mechanical Engineering
• Term: Funded in 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 523842938

The mechanical behavior of materials, structures or structural joint often differs under fast, high-rate dynamic loading compared to quasi-static loading. This is referred to as the so-called strain rate effect, which can lead to significant increases in strength at high test velocities, especially in the case of fiber-reinforced composite materials. Stiffness, elongation at break and failure modes can also differ at different strain rates. Knowledge of such strain rate effects of the materials is essential in the area of ​​structural crash and impact behavior.For such an experimental characterization, a servo-hydraulic dynamic high-rate testing machine is used, which is the subject of this proposal. A coupon or structural specimen is clamped in such a testing machine as in any conventional testing machine. However, the upper specimen clamping is strongly accelerated by means of hydraulic pressure before the load is abruptly introduced into the specimen. High-speed testing machines in the 160 kN performance class for high-strength fiber composite materials reach speeds of up to 20 m/s, which means that, depending on the specimen geometry, strain rates of up to approx. 600 1/s are typically realized (for comparison: quasi-static tests are carried out in the range of approx. 0.001 1/s ).For the data acquisition and measurement recording of force-displacement or stress-strain signals, a high-speed data recorder with a sufficiently high recording frequency is required and part of the system in order to record a sufficiently large number of data points during the test, which lasts only a few milliseconds. An optical high-speed measuring system based on the stereo correlation of two high-speed cameras (Digital Image Correlation) is typically used for the strain measurement.The procurement of this high-speed testing machine with an optical high-speed measuring system is part of the new appointment of Prof. Heimbs to the TU Braunschweig and is necessary for the scientific research activities of the Institute of Aircraft Design and Lightweight Structures (IFL) in the field of transient dynamics.Prof. Heimbs is a proven expert in this field and is developing it after his appointment at the IFL and expanding his extensive previous research activities. Numerous research projects are in planning and some have already been approved, which deal with the highz-rate dynamic characterization of lightweight and fiber composite materials as well as joining technologies, for example for innovative wing structures under bird strike loads, for new types of energy absorbers or for new methods of material modeling with strain rate-dependent intra- and interlaminar strengths and fracture energies for finite element simulations.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Hochgeschwindigkeitsprüfmaschine
• Instrumentation Group: 2910 Dynamische Prüfmaschinen und -anlagen, Pulser
• Applicant Institution: Technische Universität Braunschweig
• Leader: Professor Dr.-Ing. Sebastian Heimbs