Scaling of a compliant mechanism for high-precision force measurement applications. - In: Engineering for a changing world, (2023), 1.4.013, S. 1-10
This paper is dedicated to the mechanical structure of a force transducer for the measurement of very small forces in the nanonewton range with highest resolution and lowest measurement uncertainty. To achieve this, a low stiffness in one direction of motion, but high stiffness in all other directions of motion is required. Existing solutions that meet the requirements are not suitable because of their overall dimensions. This results in a need for miniaturization. For this purpose, the scaling behavior of an existing monolithic compliant mechanism is investigated and it is verified which joint contour provides an optimal stiffness ratio. It is shown that the corner-filleted contour in general has lower bending stiffnesses, but also lower cross stiffnesses compared to the semi-circular contour. A nonlinear scaling effect for the ratio of bending stiffness and cross stiffness in corner-filleted contour offers optimization potential. Based on a simplified rigid body model, additionally, the miniaturization of the mechanism is optimized. The stiffness in the desired direction of motion is reduced by about 85% compared to a semi-circular contour. The result is promising for the further development of a miniaturized force transducer. The findings of this work contribute to the advancement of the measurement of low forces and offer new perspectives for future research in miniaturized force sensors.
https://doi.org/10.22032/dbt.58847
Development of a high precision electrostatic force balance for measuring quantity of dispensed fluid as a new calibration standard for the becquerel. - In: Engineering for a changing world, (2023), 1.3.097, S. 1-16
The 2019 redefinition of the kilogram not only changes the way mass is defined but also broadens the horizon for a direct realization of other standards. The True Becquerel project at the National Institute of Standards and Technology (NIST) is creating a new paradigm for realization and dissemination of radionuclide activity. Standard Reference Materials for radioactivity are supplied as aqueous solutions of specific radionuclides which are characterized by massic activity in the units becquerel per gram of solution, Bq/g. The new method requires measuring the mass of a few milligrams of dispensed radionuclide liquid. An electrostatic force balance is used, due to its suitability for a milligram mass range. The goal is to measure the mass of dispensed fluid of 1 mg to 5 mg with a relative uncertainty of less than 0.05 %. A description of the balance operation is presented. Results of preliminary measurements with a reference mass indicate relative standard deviations less than 0.5 % for tens of tests and differ 0.54 % or less from an independent measurement of the reference mass.
https://doi.org/10.22032/dbt.59188
Wireless intelligent sensors based in nanostructures with energy self-sufficiency to study the consequences of high temperatures in combustion motors. - In: Engineering for a changing world, (2023), 1.3.073, S. 1-18
In this research are proposed the consequences of high temperatures in Internal Combustion Motors (ICM) as correlation of its performance according to give information of the ICM fault detector, which also can be useful for preventive maintenance. It was possible to achieve the proposed target because of it was designed a smart sensor based in nanostructures prepared over Anodic Aluminum Oxide (AAO) samples, which proportionated short response time and high robustness in the measurement tasks of the smart sensor, as well as, the designed sensor has the possibility to work by energy self-sufficiency and sending the measurement data to external users by wireless. In fact, it is waited that this research could be a support for researchers of ICM enhancement, who could look for new techniques of environment conditions cares in compensation to keep the balance between the useful energy obtained from ICM and the environment conditions, where are developed economical activities such as public transport or mining in Peru.
https://doi.org/10.22032/dbt.58731
Empirical study on DED-Arc welding quality inspection using airborne sound analysis. - In: Engineering for a changing world, (2023), 1.3.055, S. 1-12
This study explores the potential of audible range airborne sound emissions from Gas Metal Arc Welding (GMAW) to create an automated classification system using neural networks (NN) for weld seam quality inspection. Irregularities in GMAW process (oil presence, insufficient shielding gas) may lead to porosity imperfections in weld seams. Using Directed Energy Deposition-Arc additive manufacturing, aluminum (Al) and steel wall structures were produced with varying shielding gas flows or applying oil. Acoustic emissions (AE) generated during the welding process were captured using audible to ultrasonic range microphones. Mel spectrograms were computed from the AE data to serve as input to NN during training. The proposed model achieved notable accuracies in classifying both Al weld seams (83% binary, 68% multi-class) and steel welds (82% binary, 58% multi-class). These results demonstrate that employing audible range AE and NN in GMAW monitoring offers a viable method for low-latency monitoring and valuable insights into improving welding quality.
https://doi.org/10.22032/dbt.58732
Investigation of a novel monolithic stiffness-compensated mechanism for high-precision load cells. - In: Engineering for a changing world, (2023), 1.3.017, S. 1-12
Increasing demands in the fields of high-precision force measurement and weighing technology require an ever-higher measurement resolution, a larger measurement range, a lower measurement uncertainty, and traceability to a natural constant. Load cells using the compensation principle have the potential to fulfill these requirements. To enhance the measurement resolution and decrease the measurement uncertainty, the residual stiffness of the compliant mechanism in use needs to be compensated. Due to a lack of solutions in the state of the art, a novel monolithic stiffness-compensated mechanism for measurements according to the compensation principle was developed. Simulations show a stiffness reduction to 0.2%of the initial value, a theoretical force resolution of 31 pN, and applicability for any orientation in the gravity field. Experimental investigations on a prototype confirmed the existing potential. However, further optimization of the mechanism is required to negate the effects of manufacturing deviations.
https://doi.org/10.22032/dbt.58735
Insights into the writing process of the mask-free nanoprinting fluid force microscopy technology. - In: Engineering for a changing world, (2023), 1.2.118, S. 1-13
Platelets are activated immediately when contacting with non-physiological surfaces. Minimization of surface-induced platelet activation is important not only for platelet storage but also for other blood-contacting devices and implants. Chemical surface modification tunes the response of cells to contacting surfaces, but it requires a long process involving many regulatory challenges to transfer into a marketable product. Biophysical modification overcomes these limitations by modifying only the surface topography of already approved materials. The available large and random structures on platelet storage bags do not cause a significant impact on platelets because of their smallest size (only 1-3 μm) compared to other cells. We have recently demonstrated the feasibility of the mask-free nanoprint fluid force microscope (FluidFM) technology for writing dot-grid and hexanol structures. Here, we demonstrated that the technique allows the fabrication of nanostructures of varying features. Characteristics of nanostructures including height, width, and cross-line were analyzed and compared using atomic force microscopy imaging. Based on the results, we identified several technical issues, such as the printing direction and shape of structures that directly altered nanofeatures during printing. We confirmed that FluidFM is a powerful technique to precisely fabricate a variety of desired nanostructures for the development of platelet/blood-contacting devices if technical issues during printing are well controlled.
https://doi.org/10.22032/dbt.58725
Influence of the processing on the properties of continuous fiber reinforced thermoplastic sheets prepared by extrusion. - In: AIP conference proceedings, ISSN 1551-7616, Bd. 2884 (2023), 1, 050005, S. 050005-1-050005-14
Continuous fiber reinforced thermoplastics (CFRT) are composite materials consisting of continuous fibers and a thermoplastic matrix and offer outstanding mechanical properties, low densities, short cycle times and recyclability. CFRT can be classified into unidirectional tapes and sheets utilizing various semi-finished textiles as reinforcement. CFRT sheets are of interest for area measured products or multiaxial loads. Various discontinuous and semi-continuous methods to prepare CFRP sheets are described in the literature. All these methods either feature high cycle times or high investment costs and require double melting of the polymer, e.g., first to produce a polymer film and second to produce the CFRT sheet. An energy efficient alternative to produce CFRT sheets is extrusion, which allows to spare one melting step. A twin-screw extruder melts the polymer, which is then conveyed by a melt pump to the film extrusion dies and applied to both sides of the semi-finished textile, which is wetted and consolidated using a calendar. Due to the high melt viscosity and the line load at the calendar the major challenge is to achieve full void-free impregnation of the semi-finished textile. The mechanical properties of a CFRT sheet are determined by fiber and void volume content. Hence, the influence of the processing conditions on the fiber and void volume content as well as the mechanical properties were examined applying a parametric study of the die temperature, the haul-off speed, and the gap between the calendar rolls. The properties of the extruded CFRT sheets were compared to compression molded sheets. The fiber volume content was directly adjusted by the haul-off speed and the extruder throughput. An increasing die temperature lowers the melt viscosity and results in an increased fiber volume content. Scanning electron microscopy shows complete macro impregnation between the fiber bundles but not completely wetted individual filaments within fiber bundles.
https://doi.org/10.1063/5.0168183
Einseitiges Widerstandsschweißen von Kunststoff und Metall - mechanische Eigenschaften und Oberflächenwechselwirkung. - In: DVS Congress 2023, (2023), S. 788-796
Kurzfassung S. 40
Akustische Kontrolle von Rührreibschweißnähten im Rahmen der Qualitätssicherung. - In: DVS Congress 2023, (2023), S. 641-649
Kurzfassung S. 33
Charakterisierung der geometrischen Verschleißeigenschaften von Rührreibschweißwerkzeugen und Entwicklung einer Methodik zur Abschätzung des maximal ertragbaren Verschleißes. - In: DVS Congress 2023, (2023), S. 634-640
Kurzfassung S. 32