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Aufsatz
Miniaturized interferometric confocal distance sensor for surface profiling with data rates at ultrasonic frequencies
(2023-01-12)
Point-wise measuring profilometers like the tactile stylus instruments or optical sensors are established measurement tools in science and industry to measure and characterize surface textures. We present a fiber-coupled laser interferometric confocal distance sensor for surface profiling. The sensor is characterized by small geometric dimensions and by its high lateral
scanning speed. The ability to measure specularly reflecting and rough surface textures are demonstrated by performing several measurements on a ...
Aufsatz
Model-based investigations of ferroelectric energy harvesting with regard to an improvement of life span and operability
(2023-02-13)
A new ferroelectric energy harvesting concept is investigated theoretically, based on a thermo-electromechanical multiscale constitutive framework in connection with the so-called condensed method. Taking advantage of comparatively large changes of strain and polarization due to domain switching, the electric output is higher compared to what is commonly known as
piezoelectric energy harvesting. Dissipative self-heating and augmented damage accumulation, on the other hand, may impede the operability of the harvesting ...
Aufsatz
Experimental and numerical polarization analysis of the 3D transfer behavior in microsphere-assisted interferometry for 1D phase gratings
(2023-06-08)
Enhancing the lateral resolution in optical microscopy and interferometry is of great interest in recent research. In order to laterally resolve structures including feature dimensions below the Abbe resolution limit, microspheres in the optical near-field of the specimen are shown to locally improve the resolution of the imaging system. Experimental and simulated results following this approach are obtained by a high NA Linnik interferometer and analyzed in this contribution. They show the reconstructed surface of ...
Aufsatz
Time Series Optimization-Based Characteristic Curve Calculation for Local Reactive Power Control Using Pandapower-PowerModels Interface
(2023-05-29)
Local reactive power control in distribution grids with a high penetration of distributed energy resources (DERs) will be essential in future power system operation. Appropriate control characteristic curves for DERs support stable and efficient distribution grid operation. However, the current practice is to configure local controllers collectively with constant characteristic curves that may not be efficient for volatile grid conditions or the desired targets of grid operators. To address this issue, this paper ...
Aufsatz
Influence of Different Hot Runner-Systems in the Injection Molding Process on the Structural and Mechanical Properties of Regenerated Cellulose Fiber Reinforced Polypropylene
(2023-04-18)
The increasing demand for renewable raw materials and lightweight composites leads to an increasing request for natural fiber composites (NFC) in series production. In order to be able to use NFC competitively, they must also be processable with hot runner systems in injection molding series production. For this reason, the influences of two hot runner systems on the structural and mechanical properties of Polypropylene with 20 wt.% regenerated cellulose fibers (RCF) were investigated. Therefore, the material was ...
Aufsatz
Development of a hybrid mixed-mode solar dryer for product drying
(2023-02-28)
Sun drying in the open air is quite popular worldwide. However, the use of solar dryers to preserve various perishable agricultural products is a relatively new area of study, and the long-term effects of this method are not yet fully understood. The slow drying process in direct sunlight can contaminate the dried materials by soil and insects. To overcome these challenges, we devised a sun drying system that included a heating part, a drying area, a portable stand, fans, and a 50-W photovoltaic panel. An alternate ...
Aufsatz
Emission and Mechanical Properties of Glass and Cellulose Fiber Reinforced Bio-Polyamide Composites
(2023-06-07)
Climate change, access, and monopolies to raw material sources as well as politically motivated trade barriers are among the factors responsible for a shortage of raw materials. In the plastics industry, resource conservation can be achieved by substituting commercially available petrochemical-based plastics with components made from renewable raw materials. Innovation potentials are often not used due to a lack of information on the use of bio-based materials, efficient processing methods, and product technologies ...
Aufsatz
Prediction Model Based on DoE and FTIR Data to Control Fast Setting and Early Shrinkage of Alkaline-Activated Slag/Silica Fume Blended Cementitious Material
(2023-05-31)
This study aims to develop a material-saving performance prediction model for fast-hardening alkali-activated slag/silica fume blended pastes. The hydration process in the early stage and the microstructural properties after 24 h were analyzed using design of experiments (DoE). The experimental results show that the curing time and the FTIR wavenumber of the Si-O-T (T = Al, Si) bond in the band range of 900–1000 cm−¹ after 24 h can be predicted accurately. In detailed investigations, low wavenumbers from FTIR analysis ...
Aufsatz
Dissimilar Laser Beam Welding of Titanium to Stainless Steel Using Pure Niobium as Filler Material in Lap Joint Configuration
(2023-09-20)
In the present investigation, commercially pure titanium is welded to AISI 316L stainless steel by intermixing niobium as filler material in a lap joint configuration. For this purpose, a pulsed Nd:YAG laser with various pulse durations and pulse peak powers is employed to obtain different mixing conditions for the materials. It will be demonstrated that, despite the implementation of the filler material, the weld seams are characterized by a high affinity for cracking, which in turn can be attributed to the formation ...
Aufsatz
FEM–CM as a hybrid approach for multiscale modeling and simulation of ferroelectric boundary value problems
(2023-06-05)
Constitutive modeling of ferroelectrics is a challenging task, spanning physical processes on different scales from unit cell switching and domain wall motion to polycrystalline behavior. The condensed method (CM) is a semi-analytical approach, which has been efficiently applied to various problems in this context, ranging from self-heating and damage evolution to energy harvesting. Engineering applications, however, inevitably require the solution of arbitrary boundary value problems, including the complex multiphysical ...