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A Critical Review and Assessment of Different Thermoviscoplastic Material Models for Simultaneous Hot/Cold Forging Analysis
(2020-05-26)
The simultaneous hot/cold forging is an innovative production process, taking advantage of the high accuracy for cold forming and low forces for hot forming. However, the choice of a suitable material model for such a large temperature range is a difficult issue and insufficiently regarded. Hence, the aim of this contribution is a critical review and assessment of the prediction capability and accuracy of three already existing thermo-viscoplasticity models. Therefore, the simulation results of the Bammann, Chiesa ...
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SimBench—A Benchmark Dataset of Electric Power Systems to Compare Innovative Solutions Based on Power Flow Analysis
(2020-06-26)
Publicly accessible, elaborated grid datasets, i.e., benchmark grids, are well suited to publish and compare methods or study results. Similarly, developing innovative tools and algorithms in the fields of grid planning and grid operation is based on grid datasets. Therefore, a general methodology to generate benchmark datasets and its voltage level dependent implementation is described in this paper. As a result, SimBench, a comprehensive dataset for the low, medium, high and extra-high voltage level, is presented. ...
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Influence of hot deformation on the precipitation hardening of high-strength aluminum AA7075 during thermo-mechanical processing
(2021-04-21)
The aim of this work was to investigate the effect of hot deformation on the aging behavior of precipitation-hardenable aluminum alloy AA7075 within a novel thermo-mechanical forming process, in order to gain insight into its precipitation kinetics. For this purpose, the material was formed at 420 °C after undergoing solution treatment to different strain levels ranging from 2% to 10% to obtain different dislocation densities. After undergoing hot deformation, aging at 120 °C with different parameters was carried out ...
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Experimentelle Untersuchung zur Mehrphasenströmung in öleingespritzten Mehrphasenschraubenspindelpumpen
(2020-02-18)
Für die Förderung von Gemischen mit hohen Gasanteilen erfolgt die Entwicklung eines neuen Kühlkonzepts, indem das Prozessfluid in flüssiger Phase extern in die Förderkammer einer Mehrphasenpumpe eingespritzt wird. Neben der Regulierung des Thermomanagements trägt dies zur Spaltabdichtung bei, so dass der effektiv geförderte Volumenstrom steigt. Zur Untersuchung der Thermo‐ und Fluiddynamik einer solchen Mehrphasenpumpe wird ein transparentes Förderkammermodell der Pumpe mit externer Fluideinspritzung entwickelt. Das ...
Aufsatz
On the Evolution of Residual Stresses, Microstructure and Cyclic Performance of High-Manganese Austenitic TWIP-Steel after Deep Rolling
(2019-07-25)
The mechanical properties and the near surface microstructure of the high-manganese twinning-induced plasticity (TWIP) steel X40MnCrAl19-2 have been investigated after deep rolling at high (200 ∘C ), room and cryogenic temperature using different deep rolling forces. Uniaxial tensile tests reveal an increase in yield strength from 400 MPa to 550 MPa due to surface treatment. The fatigue behavior of selected conditions was analyzed and correlated to the prevailing microstructure leading to an increased number of cycles ...
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Grain-Size Specific Characterisation and Resource Potentials of Municipal Solid Waste Incineration (MSWI) Bottom Ash: A German Case Study
(2020-05-31)
Municipal solid waste incineration (MSWI) is a major element of modern waste management and produces annually around 5.7 million tonnes of bottom ash (BA) in Germany. In order to save natural resources and protect the environment, utilisable materials need to be recovered from BA. It was the aim of the present study to determine metal and mineral resource potentials of MSWI BA based on a characterisation study of raw and aged BA of the MSWI plant in Kassel (Germany). The BA investigated consisted of 82.2% mineral ...
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Improving Vertical Wind Speed Extrapolation Using Short-Term Lidar Measurements
(2020-03-29)
This study investigates how short-term lidar measurements can be used in combination with a mast measurement to improve vertical extrapolation of wind speed. Several methods are developed and analyzed for their performance in estimating the mean wind speed, the wind speed distribution, and the energy yield of an idealized wind turbine at the target height of the extrapolation. These methods range from directly using the wind shear of the short-term measurement to a classification approach based on commonly available ...
Aufsatz
Laser welding of grey cast iron with spheroidal graphite-influence of process parameters on crack formationand hardness
(2021-03-24)
In the investigation at hand, sheets of ferritic and pearlitic grey cast iron with spheroidalgraphite are welded using a fiber-laser. The influence of varying laser power and welding speed onthe macroscopic characteristics of the weld seam and crack formation are analyzed and discussed.Substantial crack formation with crack densities of up to2.93 cm−1are found. Furthermore, hardnessmeasurements are conducted to evaluate the formation of brittle phases within the weld metaland heat-affected zone. Peak hardness values ...
Aufsatz
High-Speed Laser Cladding on Thin-Sheet-Substrates—Influence of Process Parameters on Clad Geometry and Dilution
(2021-08-09)
Laser-based Directed Energy Deposition (DED-LB) represents a production method of growing importance for cladding and additive manufacturing through the use of metal powders. Yet, most studies utilize substrate materials with thicknesses of multiple millimeters, for which laser cladding of thin-sheet substrates with thicknesses less than 1 mm have only been scarcely studied in the literature. Most studies cover the use of pulsed laser sources, since sheet distortion due to excess energy input is a key problem in laser ...
Aufsatz
Comparison Between Two Hydrodynamic Models in Simulating Physical Processes of a Reservoir with Complex Morphology: Maroon Reservoir
(2020-03-14)
Two 3D hydrodynamic models, AEM3D and MIKE3, are compared in simulating hydrodynamics of the Maroon Reservoir in southwest Iran. The reservoir has a complex bathymetry with steep walls, which makes it a good case for studying the performance of hydrodynamic models. The models were compared together and with measured water temperatures from different locations of the reservoir in a five-month period between December 2011 and April 2012. The results indicated that the AEM3D model, which uses a finite difference scheme ...