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Aufsatz
Tailoring flow behavior and heat transfer in tempering channels for high-pressure die casting—analysis of potentials of commercial static mixers and prospects of additive manufacturing
(2023-02-16)
Additive manufacturing (AM) opens up manifold possibilities to influence the heat transfer between fluid and die in high-pressure die casting (HPDC), eventually allowing to minimize the total cycle time of the process. AM already has been exploited to establish near-contour temperature control systems in industrial applications. However, AM not only allows to influence the position of tempering channels in dies but it also allows to influence the fluid dynamics itself, e.g., by imprinted static mixers. Up to now, ...
Aufsatz
Data Driven prediction of forced nonlinear vibrations using stabilised Autoregressive Neural Networks
(2023-03-24)
In this work, we propose a novel approach to the data-driven prediction of vibration responses of nonlinear systems. The main idea is based on Autoregressive Neural Networks (ARNN) to model the nonlinear transfer behaviour between an external excitation and the system response. We propose an autoregressive network architecture with embedded symmetry using bias-free tanh activation and guarantee Input-to-State-Stability (ISS) by enforcing a special penalty term to the weights. The resulting training procedure is ...
Aufsatz
An Investigation on Limiting Potentials for Damage Prediction of Viscoelastic Adhesives
(2023-03-24)
In his recent work VOLOKH introduced the energy limiting method as an alternative to continuum damage mechanics developed and envolved by KACHANOV, RABOTNOV, LEMAITRE and many more. In contrast to continuum damage mechanics, the energy limiting method is physically grounded by the process of atomistic debonding and, therefore, motivated on an energy basis. In order to use the energy limiting method within the framework of continuum mechanics, a limiting potential needs to be defined, which can be seen as a macroscopic ...
Aufsatz
Consideration of nonlinear multipoint constraints in finite element analyses based on a master-slave elimination scheme operating at the global level
(2023-03-24)
A method to consider nonlinear multipoint constraints in finite element analysis based on a master-slave elimination scheme operating at the global level is presented. We focus on systems with nonlinear constraints in which the number of constraints is of the same order of magnitude as the number of degrees of freedom. Therefore, we rely on the master-slave elimination which gives us the huge benefit of drastically reducing the problem size. In the literature the presented master-slave elimination schemes for linear ...
Aufsatz
Evaluation of hydraulic efficiency of lined irrigation channels - A case study from Punjab, Pakistan
(2023-04-04)
Indus Basin Irrigation System (IBIS) in Pakistan is the backbone of agriculture in the country. The IBIS provides irrigation support to agricultural lands across the country; however, hydraulic efficiency of the water conveyance system is impacted due to seepage losses. The lining of irrigation channels is considered a potential solution for improving hydraulic efficiency. Therefore, this study explores the impact of canal lining on the hydraulic efficiency of the canals in the Punjab province of Pakistan. Overall, ...
Aufsatz
Experimentelle Untersuchungen von Wärmerohrsystemen für den Einsatz in elektrischen Arbeitskraftmaschinen
(2023-03-01)
Mit dem Ziel die Effizienz elektrischer Arbeitskraftmaschinen durch ein innovatives Kühlsystem zu erhöhen, wird ein Wärmetransportsystem auf Basis von Wärmerohren entwickelt und analysiert. Die Leistungsfähigkeit des Systems bei Variation des Temperaturbereichs und des zugeführten Wärmestroms sowie der Einfluss der Rotation werden experimentell untersucht. Der Wärmewiderstand des Systems wird im Vergleich zu reiner Wärmeleitung um 98 % reduziert. Die Rotation des Systems hat keinen signifikanten Einfluss auf den ...
Aufsatz
Electrostatic Body Forces and their Implications for Cracks
(2023-03-24)
A Griffith-type crack in a dielectric solid under electromechanical loading is investigated by numerically solving the combined boundary value problem. The focus is on the contribution of electrostatically induced body forces, coming along with the still controversially discussed Maxwell stress tensor, to the crack tip loading. A 1/r-singularity of compressive stress is found to evolve at the crack tip, however, just being dominant over the mechanically induced 1/√r-behavior within a very small region
Aufsatz
Study of Dynamics in Metallic MEMS Cantilevers - Pull-In Voltage and Actuation Speed
(2023-01-13)
For different metals and varying geometries, this paper presents simulations of electrostatically actuated MEMS cantilevers regarding their influence on pull-in voltage and actuation speed. Three-dimensional electromechanical modeling including many non-linearities has been performed to study some static but mainly dynamic features. The results show that the involved parameters have different influences on the actuation speed and pull-in voltage: lower length, higher thickness as well as lower density and higher ...
Aufsatz
Potential of Fe-Mn-Al-Ni Shape Memory Alloys for Internal Prestressing of Ultra-High Performance Concrete
(2023-05-18)
Prestressing of concrete is a commonly used technique in civil engineering to achieve long spans, reduced structural thicknesses, and resource savings. However, in terms of application, complex tensioning devices are necessary, and prestress losses due to shrinkage and creep of the concrete are unfavourable in terms of sustainability. In this work, a prestressing method using novel Fe-Mn-Al-Ni shape memory alloy rebars as a tensioning system in UHPC is investigated. A generated stress of about 130 MPa was measured ...
Aufsatz
Flexible Electrochromic Device on Polycarbonate Substrate with PEDOT:PSS and Color-Neutral TiO2 as Ion Storage Layer
(2023-04-22)
Electrochromic (EC) windows on glass for thermal and glare protection in buildings, often referred to as smart (dimmable) windows, are commercially available, along with rearview mirrors or windows in aircraft cabins. Plastic-based applications, such as ski goggles, visors and car windows, that require lightweight, three-dimensional (3D) geometry and high-throughput manufacturing are still under development. To produce such EC devices (ECDs), a flexible EC film could be integrated into a back injection molding process, ...