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Micro-sheartester (µST)

The micro-sheartester was developed at the iPAT to determine flow behavior of very small amounts of powder. Contrary to common shear devices the µST can be applied to investigate sample volumes in the range between 6 and 15 µL. Thus the µST is well suitable for screening processes of new developed powders without large amount of sample volumes. Furthermore the µST can be combined with a X-ray-computed tomography device for in situ measurements helpful for non-destructible investigations of microstructure regarding to meso- and particle level. Therefore the µST performs a rotational movement using a torsional geometry between upper and lower piston which causes a shear deformation within the sample. The loading is conducted by accurate controlled piezo engines. Here a decoupling of sample loading (upper piston) and force detection (lower piston) is implemented to determine the flow properties. The benefit of this decoupling method is the negligence or at least the reduction of interference factors, e.g. friction behavior of single components. Here, the lower piston which measures the torque, and the normal and shear stresses is frictionless beared. The precision of the µST is astonishing during measuring and positioning with lower than one micron. Furthermore the accuracy of force determination is lower than one mN and the measurement range of torque is lower than one nNm. Moreover the µST is able to load and detect normal and shear forces within the range of 0.1 and 20 kPA.


Figure: Micro-sheartester with sample chamber of glass