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Torres Melgarejo, Mario André; Darnieder, Maximilian; Linß, Sebastian; Zentner, Lena; Fröhlich, Thomas; Theska, René
On modeling the bending stiffness of thin semi-circular flexure hinges for precision applications. - In: Actuators, ISSN 2076-0825, Bd. 7 (2018), 4, 86, S. 1-16

Compliant mechanisms based on flexure hinges are widely used in precision engineering applications. Among those are devices such as precision balances and mass comparators with achievable resolutions and uncertainties in the nano-newton range. The exact knowledge of the mechanical properties of notch hinges and their modeling is essential for the design and the goal-oriented adjustment of these devices. It is shown in this article that many analytical equations available in the literature for calculating the bending stiffness of thin semi-circular flexure hinges cause deviations of up to 12% compared to simulation results based on the three-dimensional finite element model for the considered parameter range. A close examination of the stress state within the loaded hinge reveals possible reasons for this deviation. The article explains this phenomenon in detail and shows the limitations of existing analytical models depending on specific geometric ratios. An accurate determination of the bending stiffness of semi-circular flexure hinges in a wide range of geometric parameters without the need for an elaborate finite element analysis is proposed in form of FEM-based correction factors for analytical equations referring to Euler-Bernoulli's beam theory.



https://doi.org/10.3390/act7040086
Fern, Florian; Füßl, Roland; Schienbein, Ralf; Theska, René
Influence of additional rotational movements on the measurement uncertainty of nanomeasuring, nanopositioning and nanofabrication machines. - In: Sensors and Measuring Systems, (2018), S. 168-171

The measurement of freeform surfaces, aspheric lenses or the sidewall roughness of high aspect ratio structures are a current challenge in nanometrology. There are different publications and commercial products with approaches to perform a measurement of those quantities [1, 2, 3, 4]. Beside the nanomeasurement the nanofabrication on curved freeform surfaces is an upcoming trend. The measurement or the fabrication on a freeform surface is limited by the possible tilt angle between the tools working axis and the local surface normal. To achieve larger angles and a minimal measurement uncertainty the tool must be placed optimal to the local surface. According to those requirements, concepts are developed to increase the degree of freedom in positioning. The x-y-z translational positioning system of an nanomeasuring machine (NMM-1) with a working volume of 25×25×5mm^3 [5] will be extended by additional rotational movements. The rotation can be achieved by three basic principles of motion which are the rotation of the sample, of the tool or a combination of the tool and the sample rotation. In a first step the principles of motion are described by their bare geometrical properties and decoupled from real positioning systems. A constant instantaneous centre of motion in the sensor measurement point is determined as the optimal principle for a rotational system. This principle is further investigated and is made concrete by choosing a combination of kinematics [6]. A vectorial approach based on the GUM [7] is used to evaluate the influence of the axes error motion on the measurement result. The method and the results for a combination of a rotary table and a goniometer axis are described in detail.



https://ieeexplore.ieee.org/document/8436163
Hahm, Christoph; Theska, René; Fehringer, Andreas; Kästner, Anett
Qualification of the endurance strength enhancement of silane coated concrete parts. - In: Measurement science and technology, ISSN 1361-6501, Bd. 29 (2018), 10, S. 104003, insges. 9 S.

https://doi.org/10.1088/1361-6501/aad6c1
Scharff, Moritz; Darnieder, Maximilian; Steigenberger, Joachim; Alencastre, Jorge H.; Behn, Carsten
Theoretical investigations on the behavior of artificial sensors for surface texture detection. - In: Dynamical systems in theoretical perspective, (2018), S. 311-321

Animal vibrissae are used as natural inspiration for artificial tactile sensors, e.g., the mystacial vibrissae enable rodents to perform several tasks in using these tactile hairs: object shape determination and surface texture discrimination. Referring to the literature, the Kinetic Signature Hypothesis states that the surface texture detection is a highly dynamic process. It is assumed that the animals gather information about the surface texture out of a spatial, temporal pattern of kinetic events. This process has to be analyzed in detail to develop an artificial tactile sensor with similar functionalities. Hence, we set up a mechanical model for theoretical investigations of the process. This model is analyzed in two different directions using numerical simulations: at first a quasi-static and then a fully dynamic description.



https://doi.org/10.1007/978-3-319-96598-7_25
Hahm, Christoph; Theska, René; Raab, Dagmar; Fehringer, Andreas; Kästner, Anett
Experimental qualification of the strength enhancement of coated concrete parts. - In: Proceedings of the 18th International Conference of the European Society for Precision Engineering and Nanotechnology, (2018), S. 147-148

Gräser, Philipp; Linß, Sebastian; Räder, Thomas; Zentner, Lena; Theska, René
Investigations of the geometrical scaling in the systematic synthesis of compliant mechanisms. - In: Proceedings of the 18th International Conference of the European Society for Precision Engineering and Nanotechnology, (2018), S. 67-68

Schienbein, Ralf; Weigert, Florian; Fern, Florian; Theska, René; Füßl, Roland
The implementation of ultra precision rotations to multiaxial nanofabrication machines: challenges and solution concepts. - In: Proceedings of the 18th International Conference of the European Society for Precision Engineering and Nanotechnology, (2018), S. 65-66

Existing long-range nanopositioning and nanomeasuring machines are based on three independent linear movements in a Cartesian coordinate system. This in combination with the specific nature of sensors and tools (further on summarized as tool) limits the addressable part geometries. This article contributes to the enhancement of multiaxial machine structures by the implementation of rotational movements while keeping the precision untouched. A parameter based dynamic evaluation system with quantifiable technological parameters has been set up and employed to identify general solution concepts and adequate substructures. First evaluations show high potential for sample scanning mode variants considering linear movements of the object in combination with angular movements of the tool, considering a goniometer setup in specific. The evaluation system is further enhanced by the implementation of data based on comprehensive design catalogues, uncertainty calculations and CAD-model based footprint analysis for specific setups. To support the selection, detailed parameter sets are generated containing explicit moving ranges, uncertainties, resolutions, reproducibilities and costs. This approach is also applied to the rotation of the object. The results are compared to the tool rotation and mixed versions. After all, the knowledge gained, is formed into general rules for the verification and optimization of design solutions for multiaxial nanopositioning machines.



Darnieder, Maximilian; Torres, Mario; Linß, Sebastian; Theska, René
On precise modelling of very thin flexure hinges. - In: Proceedings of the 18th International Conference of the European Society for Precision Engineering and Nanotechnology, (2018), S. 87-88

The continuously rising demands for precision favour the application of monolithic compliant mechanisms with flexure hinges in various fields of precision engineering. It gives way to an almost frictionless and precise motion even under vacuum conditions. These advantages have made compliant mechanism an integral component of high precision weighing cells. A downside of compliant joints is their stiffness towards deflection, which limits the sensitivity of the overall system. Consequently, the flexure hinges are manufactured as thin as possible. The present limit in terms of manufacturing technology is within the range of 50 [my]m. The objective of predicting the behaviour of highest precision weighing cells by modelling is directly interconnected with the exact knowledge of the behaviour of flexure hinges in terms of stiffness. Especially, for flexure hinges with high aspect ratios, typically found in weighing cells, the existing analytical equations and finite element models show pronounced deviations. The present research effort is dedicated to a clarification of this observation. Structure mechanical finite element models are developed to identify the deviations of the models precisely. Results obtained are compared to analytical results and conclusions for the modelling of thin flexure hinges are drawn.



Linß, Sebastian; Gräser, Philipp; Räder, Thomas; Henning, Stefan; Theska, René; Zentner, Lena
Influence of geometric scaling on the elasto-kinematic properties of flexure hinges and compliant mechanisms. - In: Mechanism and machine theory, Bd. 125 (2018), S. 220-239

https://doi.org/10.1016/j.mechmachtheory.2018.03.008
Theska, René; Zentner, Lena; Fröhlich, Thomas; Weber, Christian; Manske, Eberhard; Linß, Sebastian; Gräser, Philipp; Harfensteller, Felix; Darnieder, Maximilian; Kühnel, Michael
State of the art precision motion systems based on compliant mechanisms. - In: The 4th International Conference Mechanical Engineering in XXI Century, (2018), S. 3-8