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Low-Cycle-Fatigue Performance of Stress-Aged EN AW-7075 Alloy
(2023-05-05)
The effect of a novel heat treatment, that is, aging under superimposed external stress, on the fatigue performance and microstructural evolution of a high-strength aluminum alloy (EN AW-7075) is presented. Stress aging, a combination of heat treatment and superimposed external stress, can enhance the mechanical properties of EN AW-7075 under monotonic loading due to the acceleration of precipitation kinetics. Scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) reveal that a longer ...
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UVC Irradiation as a Surface Treatment of Polycarbonate to Generate Adhesion to Liquid Silicone Rubber in an Overmolding Process
(2024-04-18)
This study investigates the adhesion properties of polycarbonate (PC) and liquid silicone rubbers (LSR) through surface activation using ultraviolet C (UVC) radiation. While self-adhesive LSRs adhere easily to certain thermoplastic composites such as polybutylene terephthalate (PBT) and polyamides (PAs), bonding to PC typically requires surface treatment due to the lack of compatible functional groups. Previous methods like plasma or flame treatment have been effective, but the use of UVC radiation for surface ...
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Characterization of Mechanical Properties, Macroscopic Deformation Behavior, and Microstructure of Functionally Graded 22MnB5 Steel
(2021-03-24)
The focus of this study is on the characterization of the local plastic deformation and failure of functionally graded 22MnB5 plates after hot stamping using an in situ approach. Various forming strategies at elevated temperatures are performed using differentially tempered forming tools to locally tailor the microstructure. By controlling the cooling rate, graded as well as martensitic and ferritic–pearlitic microstructures are obtained. Experimental analysis includes evaluation of the material- and geometry-dependent ...
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On the Influence of Microstructure on the Corrosion Behavior of Fe–Mn–Al–Ni Shape Memory Alloy in 5.0 wt% NaCl Solution
(2020-10-03)
Herein the corrosion behavior of Fe–Mn–Al–Ni shape memory alloys characterized by different microstructures in a 5.0 wt% NaCl solution is investigated. Open circuit potential and potentiodynamic polarisation tests are conducted. Generally, Fe–Mn–Al–Ni shows corrosion properties being similar to pure iron. However, the polarization curves of single crystals indicate the presence of an unstable passive system. The corrosion damage is analyzed by means of optical microscopy and electron microscopy. It is revealed that ...
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Receding-Horizon Control of Constrained Switched Systems with Neural Networks as Parametric Function Approximators
(2022-11-21)
This work studies receding-horizon control of discrete-time switched linear systems subject to polytopic constraints for the continuous states and inputs. The objective is to approximate the optimal receding-horizon control strategy for cases in which the online computation is intractable due to the necessity of solving mixed-integer quadratic programs in each discrete time instant. The proposed approach builds upon an approximated optimal finite-horizon control law in closed-loop form with guaranteed constraint ...
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Verbesserung der CO₂-Bilanz von Kalksandsteinen durch den Einsatz von Sägeschlamm als Optimierungszuschlag
(2023-12-06)
Rund 20% der aus den Rohstoffen Kalk, Sand und Wasser hergestellten Kalksandsteine (KS) in KS-XL-Formaten werden zur Vorkonfektionierung gesägt. Dabei fallen in den KS-Werken insgesamt rd. 20.000 t Sägeschlämme pro Jahr an, die derzeit keiner gezielten Verwendung zugeführt werden. Allerdings handelt es sich dabei bereits unter Einsatz von CO₂-intensivem Branntkalk gehärtetes Material, welches als Optimierungszusatz genutzt werden kann.
Insgesamt 13 verschiedene Sägeschlämme (SäS) wurden hinsichtlich ihrer Eignung ...
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Topology optimization considering self-weight
(2023-11-10)
In civil engineering self-weight loading usually represents the preponderant load case and shall therefore be considered in structural optimization. The present study investigates numerical topology optimization of structural stiffness with a bound on disposable amount of material. A customized topology optimization routine based on Sequential Quadratic Programming was built and is examined by means of known benchmark problems complemented by consideration of self-weight. This study aims to highlight the relevance ...
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Spatially resolved in situ analyses of the adsorption behavior of different admixtures on binders
(2023-12-06)
Admixtures play a key role in improving the performance of the cement paste matrix. A more efficient matrix can allow a reduction the binder content while maintaining the same properties. There is currently a lack of knowledge about the spatial distribution of admixtures in situ on binder surfaces which would facilitate the use of admixtures in general in inorganic binder systems. Imaging techniques such as confocal laser scanning microscopy (CLSM) and fluorescence microscopy can be used to study the spatiotemporal ...
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Quantitative analysis of the effect of foam morphology on the quasi-static and cyclic-dynamic tensile properties
(2024-02-28)
This study is the initial investigation into the relationship between the structure of foam and its quasi-static tensile and tension-tension fatigue properties. It is also the first examination of crack initiation and propagation in relation to various foam morphology patterns. The overall foam morphology and geometric appearance of the cell structure can be altered by varying the parameters of foam injection molding. Quantitative features of foam morphology are measured in terms of cell diameter, cell distance, cell ...
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PrOuD: Probabilistic Outlier Detection Solution for Time-Series Analysis of Real-World Photovoltaic Inverters
(2023-12-21)
Anomaly detection methods applied to time series are mostly viewed as black boxes that solely provide a deterministic answer for the detected target. Without a convincing explanation, domain experts can hardly trust the detection results and must conduct further time-series diagnoses in real-world applications. To overcome this challenge, we mathematically analyzed the sources of anomalies and novelties in multivariate time series as well as their relationships from the perspective of Gaussian-distributed non-stationary ...