Now showing 1 - 6 of 6
  • Publication
    Transferability of ANN-generated parameter sets from welding tracks to 3D-geometries in Directed Energy Deposition
    ( 2022-11-04)
    Marko, Angelina
    ;
    Bähring, Stefan
    ;
    Raute, Maximilian Julius
    ;
    ;
    Directed energy deposition (DED) has been in industrial use as a coating process for many years. Modern applications include the repair of existing components and additive manufacturing. The main advantages of DED are high deposition rates and low energy input. However, the process is influenced by a variety of parameters affecting the component quality. Artificial neural networks (ANNs) offer the possibility of mapping complex processes such as DED. They can serve as a tool for predicting optimal process parameters and quality characteristics. Previous research only refers to weld beads: a transferability to additively manufactured three-dimensional components has not been investigated. In the context of this work, an ANN is generated based on 86 weld beads. Quality categories (poor, medium, and good) are chosen as target variables to combine several quality features. The applicability of this categorization compared to conventional characteristics is discussed in detail. The ANN predicts the quality category of weld beads with an average accuracy of 81.5%. Two randomly generated parameter sets predicted as “good” by the network are then used to build tracks, coatings, walls, and cubes. It is shown that ANN trained with weld beads are suitable for complex parameter predictions in a limited way.
  • Publication
    Acoustic emission-based process monitoring in the milling of carbon fibre-reinforced plastics
    ( 2022)
    Uhlmann, E.
    ;
    Holznagel, Tobias
    Milling of fibre-reinforced plastics is a challenging task. The highly abrasive fibres lead to high tool wear and coating failures, which cause increasing process forces and temperatures. Machining with a worn tool, in turn, can result in unwanted workpiece damages such as delamination or fibre protrusion. Reliable monitoring of the process must therefore be able to detect damages to the milling tool and the workpiece alike. The presented process monitoring approach measures the acoustic emission generated by the milling tool cutting edge entering the workpiece with a sensor attached to the tool holder. Specific acoustic emission frequency spectra and waveforms are emitted in the cutting zone for different tool wear states. Coating failures as well as other acoustic emission events due to workpiece damages can be robustly detected and distinguished by feature extraction and signal processing as well. The developed setup, the monitoring parameterisation techniques and signal processing algorithms as well as experimental and monitoring results are presented and discussed in this paper.
  • Publication
    Introducing readiness scales for effective reuse of open source hardware
    ( 2022)
    Mies, Robert
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    ;
    Hassan, Mehera
    Open source hardware (OSH) describes physical products that allow for "anyone to study, modify, produce, and distribute them". While OSH principles aim to support design reuse, recent studies have challenged whether this is properly applied in practice. Therefore, this article delivers an assessment scheme that allows to identify the readiness of OSH designs for reuse. Testing the scheme on OSH ventilator designs collected by the Publnv ventilator project showed overall good usefulness of the scheme and emphasised the need of unambiguous assessment scales based on common standards. Less than two thirds of Publnv's listed projects fulfilled minimum criteria for openness.
  • Publication
    Micro-texture dependent temperature distribution of CVD diamond thick film cutting tools during turning of Ti-6Al-4V
    ( 2022) ;
    Schröter, D.
    ;
    Machining titanium alloys such as Ti-6Al-4V results in a high thermomechanical load on cutting tools and consequently short tool lifes. With respect to a necessary reduction of the resulting cutting tool temperatures, ultrashort pulse (USP) laser fabricated micro-textured rake faces offer direct supply of cooling lubricant into the cutting zone and lead to a reduced heat induction. As a result, micro-textured CVD diamond thick film cutting tools are also capable of machining high-performance materials due to reduced contact temperatures. In the scope of the research, the resulting temperature distribution for micro-textured rake faces will be compared under both dry and wet process conditions. Measurements show a reduction of the resulting cutting tool temperatures of Δϑt = 27.9 % using micro-textured cutting tools compared to non-textured cutting tools. A validated simulation provides valuable information about the contact temperatures enabling a specific development of the micro-texture geometry. As a result, a reduction of the contact temperature between chip and rake face by ΔϑT = 24.7 % was possible.
  • Publication
    Influence of superimposed low frequency oscillations on single-pass honing of long-chipping steel
    ( 2022)
    Uhlmann, E.
    ;
    Rozek, André
    Single-pass honing is used as a finishing process to meet high demands regarding form and dimensional accuracy of drilled bores. The disadvantages of single-pass honing compared to the conventional long-stroke honing are high process forces and torques as well as an increased risk of chip space clogging of the abrasive stones. A significant reduction in process forces and torques can be achieved by superimposing the axial movement with oscillations. In this work the kinematic basics of different oscillation parameters and their effects on single-pass honing of long-chipping steel are analyzed. It can be concluded that by superimposing low frequency oscillations in single-pass honing, the process forces and torques as well as the specific energy consumption can be reduced significantly without a decline in surface quality and form accuracy.
  • Publication
    Residual stress assessment during cutting tool lifetime of CVD-diamond coated indexable inserts
    ( 2022)
    Uhlmann, E.
    ;
    Hinzmann, Daniel
    Insufficient coating adhesion limits reproducibility regarding tool lifetime as well as workpiece quality during the application of CVD-diamond coated cutting tools. Depending on the combination of tungsten carbide substrate material, coating thickness as well as coating morphology, individual residual stress conditions exist within CVD-diamond coated cutting tool specifications. The application of these tools is accompanied by coating delamination as primary cutting tool failure. The tool lifetime of the respective cutting tool composition depends on the corresponding residual stress condition until crack development within the CVD-diamond coating initiates tool failure. During external cylindrical turning of hypereutectic aluminium silicon alloy AlSi17Cu4Mg-T6 the residual stress condition of a CVD-diamond coated cutting tool is assessed along the cutting edge, the rake face as well as flank face throughout the respective tool lifetime. Consequently, the progression of the residual stress condition until cutting tool failure regarding coating delamination is observed. During the tool lifetime of the investigated CVD-diamond cutting tools, compressive residual stress ∆σR,c shifts to tensile residual stress ∆σR,t underneath the cutting edge corner. The approximated residual stress difference of ∆σR ≈ 5 GPa indicates stress peak relaxation processes, such as crack initiation, within the CVD-diamond coating.