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A device for characterizing rotational joints in metamaterials

: Trippel, A.; Stilz, M.; Gutmann, F.; Ganzenmueller, G.C.; Hiermaier, S.


Mechanics research communications 104 (2020), Art. 103501
ISSN: 0093-6413
ISSN: 1873-3972
Fraunhofer EMI ()

This work describes a device suitable to measure torque values on the order of 10−3 Nm which are relevant in small rotational joints used in 3D-printed metamaterials. We apply this device to partially characterize a specific metamaterial, the pantograph, which is combination of planes of beams connected via pivots to form a rhomboidal lattice. Numerical and experimental studies show that the pivots’ properties dominate the macroscopic behavior of the pantograph because they store the majority of elastic and plastic strain energy. Thus, to accurately model the behavior of such a metamaterial, experimental characterization of the pivot is essential. However, a single pivot's with a typical cross section area of ~0.5 mm² results in relatively low torque which are difficult to measure with conventional, commercially rotation stages. We solve this issue with a custom-built device, specifically tailored for this application. Following a discussion of the challenges encountered in the design of this testing device, first results for 3D-printed pivots made of maraging steel MS1 are presented. Experimental results are compared to Finite-Element simulations, based on constitutive description of the bulk material's properties. The comparison indicates that such simulations are generally not representative of the experimental behavior.