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    Item type:Publication, Access status: with files ,
    Process strategies for DED-Arc-manufactured preforms of Ti-15-3-3-3 in flowforming applications
    (Multidisciplinary Digital Publishing Institute (MDPI), 2026-06-02)
    Robert Lau
    ;
    Dahms, Frederik
    ;
    Hannes Zapf
    ;
    Henrik Wünsch
    ;
    Alexander Mädje
    Arc-based directed energy deposition (DED-Arc) processes represent a promising choice for developing flexible and eco-friendly manufacturing strategies for titanium components within the aerospace sector. Previous work has predominantly focused on using Ti-6Al-4V combined with machining for structural components. This study aims to establish a hybrid manufacturing route that integrates DED-Arc with flowforming (FF), focusing on the processability of Ti-15-3-3-3 in both stages. Sinusoidal path strategies for DED-Arc yield superior results in terms of process stability and geometrical accuracy, leading to near-net-shape preforms. In the FF process, a reduction of up to 80% in wall thickness across various techniques was achieved. The hybrid approach led to a buy-to-fly (BTF) ratio of 2.5:1, revealing the potential for significant material savings compared to conventional manufacturing routes.
    Publicationtype: Journal Article
      7  4
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    Item type:Publication, Access status: with files ,
    Development and Evaluation of a LiFi-Transceiver Module for TMTC Intra-Satellite Communication †
    (Multidisciplinary Digital Publishing Institute (MDPI), 2025-03-10)
    Jahnke, Marek
    ;
    Palmer, Benjamin
    ;
    Kulau, Ulf
    The use of Light Fidelity (LiFi) can enable the reduction of satellite mass by reducing the wiring harness while avoiding electromagnetic interference. In this paper, a LiFi-transceiver suitable for Telemetry and Telecommand (TMTC) intra-satellite communication is developed and evaluated. The focus of the implementation is on miniaturization and energy-efficiency. First test results with a simple Transimpedance-Amplifier and an investigation of the achievable eff. data rate depending on different distances and Error-Correcting-Codes and the energy-consumption of the developed transceiver are presented. The results show that the LiFi-transceiver achieves a payload data rate of 77.6 kbit/s with Error-Correcting-Code protection and thus can be used for a reliable TMTC communication within the satellite bus.
    Publicationtype: Journal Article
      21  50
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    Item type:Publication, Access status: with files ,
    Design and potential analysis of an eddy current sensor for inductive conductivity measurement in fluids
    (Multidisciplinary Digital Publishing Institute (MDPI), 2021-05-19)
    Harms, Julius
    ;
    Kern, Thorsten Alexander
    In the scope of this paper, a first exemplary eddy current sensor for seawater conductivity measurement is developed, based on the derived sensor theory of a previous work. By high-frequency excitation, eddy currents are induced in the fluid and are counter-fields measured with a sensing coil. The coil’s resonance point is used for amplification. The developed prototype is analyzed based on a derived transfer function and FEM simulations. The theory is validated using a prototype implementation. With conducted experiments on a sensor test bench, the characteristics are confirmed and disturbances identified. It is shown that frequencies exist where temperature influence is minimal. This work gives a perspective for a novel sensor to allow seawater conductivity measurement.
    Publicationtype: Journal Article
    Scopus© Citations 1  125  359
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    Item type:Publication, Access status: with files ,
    Theory and modeling of eddy current type inductive conductivity sensors
    (Molecular Diversity Preservation International, 2021-05-17)
    Harms, Julius
    ;
    Kern, Thorsten Alexander
    While transformer-type conductivity sensors are the usual type of inductive sensors, this paper describes the theory behind less used eddy current sensors. This type of sensor measures the conductivity of a liquid by inducing eddy currents and observing the effect on the sensor coil, which allows a simpler sensor design and promises a cost advantage in implementation. A novel model description is derived from the Maxwell equations and implemented by an equivalent RLC circuit. The designed model is validated by comparisons with experimental observations and FEM simulations. The result leads to a better understanding of the physical effects of the sensor and the influencing parameters for future sensor developments. The aim is to provide starting points for further sensor development of low-cost inductive conductivity sensors.
    Publicationtype: Journal Article
    Scopus© Citations 2  162  601
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    Item type:Publication, Access status: with files ,
    Uncertainty analysis for low-cost transformer-type inductive conductivity sensors
    (Multidisciplinary Digital Publishing Institute (MDPI), 2021-05-17)
    Kandur, Yiğithan
    ;
    Harms, Julius
    ;
    Kern, Thorsten Alexander
    Transformer-type inductive conductivity sensors (TICS) are the industry standard for long-term conductivity measurement in fluids. This paper analyzes the potential of TICS as a low-cost alternative to the cost-effective type of conductivity cells by an implementation with reduced complexity. Sensor characteristics and performance in comparison to high precision sensor are described in the study. Linearity and hysteresis error in measurement, reproducibility and permeability influenced by the temperature change are quantified through the experiments. The results were interpreted in regard to core material, geometric properties and noise shielding. The study presented in this paper provides a better understanding of performance and uncertainty characteristics in order to improve the design of low-cost transformer-type inductive conductivity sensors.
    Publicationtype: Journal Article
    Scopus© Citations 2  110  231