149544 research outputs found
Sort by
Visual assistance system for manual composite scarf repair
No full textThe Visual assistance system for manual composite scarf repair is a assistance system. It features a automated creation of the scarf geometry icombined with a continuous deviation analysis. It can be used for complex scarfs with curved geometries and ist suitable for large repairs. It also inkluds support for additional processes
SpaceLiner 8 definition: relevant aerodynamic and aerothermodynamic issues
Get PDFThe SpaceLiner fully reusable launcher and ultra-high-speed
rocket-propelled passenger transport is in conceptual design
phase. The ongoing concept evolution is addressing system
aspects of the next configuration release 8. The challenge of the
passenger stage SLP8 design is to find an aerodynamic shape that
allows both long-range glide missions with good hypersonic L/D,
as in the case of current SpaceLiner 7, and ballistic jumps outside
the atmosphere over populated landmasses.
The paper describes the latest architecture variation of the
SpaceLiner 8 configuration still under definition. The focus is on
the aerodynamic shape evaluation with search for trimmable
designs in a very broad range of flight Mach-number and AoA.
Some of the trajectories reach up to 120 km altitude and are in the
transition regime from continuum to rarefied flow. Hence,
dedicated DSMC-calculations are performed for selected high
altitude points of the trajectory and obtained coefficients are to be
included into a refined AEDB and will subsequently be checked
on system impacts. The aerothermal issues are investigated along
different full mission profiles and suitable thermal protection
concepts are preliminarily sized and evaluated
Distributed Subsurface Imaging with Tikhonov and Total Variation Regularization for Seismic Networks
Get PDFConsistency fix: Make simd reductions SIMD-generic
No full textOne design goal of the simd interface is to enable SIMD-generic code.
This is why all arithmetic operators and functions have corresponding overloads. However, arithmetic reductions are still
missing overloads for non-simd, vectorizable types
Application of BOS velocimetry to full‑scale helicopter flight tests
Get PDFTime-resolved background-oriented schlieren (BOS) data are used to calculate the two-dimensional velocity field in the wake of free-flying full-scale helicopters in ground effect. The calculation is performed based on the density gradient pattern of the helicopter engine exhaust gas passing the BOS field of view. A classical BOS evaluation allows the visualization of density gradients such as vortices and the exhaust plume. The result is the BOS displacement field. Applying the two-dimensional divergence to these data results in a pattern that is constant in shape across multiple BOS images, but convects downstream with the outwash velocity of the helicopter. Quantitative two-dimensional velocity fields are calculated using the divergence of the BOS shift as input to a second, time-resolved evaluation. Choosing an appropriate strategy for preparing and evaluating the data is critical to a reliable velocity estimation. Another important aspect is to distinguish between reliable velocity data and erroneous results in areas of reduced signal intensity due to a lack of thermal structures. The velocity data obtained are compared with an analytical outwash model and constant temperature anemometry data acquired simultaneously with the BOS images. The data show good quantitative agreement in areas of sufficient thermal structures within the field of view. This demonstrates the feasibility of BOS velocimetry to investigate large flow fields in full-scale helicopter flight tests
Opto-Mechanical Design and Testing of a Fabry-Pérot Infrared Spectrometer
No full textThis thesis presents the development of a compact infrared spectrometer designed for planetary surface characterization. The system, based on a thermopile detector and a tunable MEMS Fabry-Perot
filter, is developed based on simulated predictions of the relevant key performance parameters, which
include signal strength, spectral resolution and the noise equivalent emissivity difference. These parameters are chosen to enable the detection of diagnostic spectral features in the thermal infrared
range, which provide insights into surface composition and structure.
The mechanical design of the sensor head, including the integration of an optical system and an
external bandpass filter, is described. Design priorities include compatibility of the sensor head with
the available optical bench for testing, thermal stability and control, as well as vacuum compatibility
to allow for testing in a mission-specific relevant environment.
A data acquisition and testing setup is implemented to operate the FPF and thermopile detector
while maintaining a controlled test environment. The influence of individual components in test
setup and sensor head is depicted and analyzed with regard to the further testing strategy. The
spectrometer’s key performance parameters, including repeatability, accuracy, signal-to-noise ratio
and signal strength, are analyzed based on measured data, giving an overview of its operational
capabilities.
Lastly, a comparison between the predicted and testing results allows for the adaption of the simulation to include setup-specific factors, such as readout electronic noise and changes of sensitivity in
the detector depending on ambient pressure, facilitating further developments of the prototype with
more accurate predictions
Development of data augmentation technique for predicting strain rate effects in the mechanical behaviour of fibre-reinforced polymer (FRP) composites (Masterarbeit)
No full textThe mechanical response of Fiber Reinforced Polymers (FRPs) under dynamic loading is crucial for structural applications, particularly in aerospace, where lightweight, high-strength materials are essential. However, accurately predicting strain-rate-dependent behavior remains challenging due to the complex material structure and the limitations of experimental and numerical methods, which are often costly, time-intensive, and sensitive to material inconsistencies. This research investigates whether a Constitutive Artificial Neural Network (CANN) can effectively model and predict the strain-ratedependent behavior of FRPs while ensuring accuracy, generalizability, and computational efficiency.
A CANN model is developed and trained using dynamic compressive testing data from cross-ply IM7/8552 composites. Unlike conventional data-driven approaches, CANNs integrate constitutive laws governing anisotropic materials, enhancing model reliability and extrapolation capabilities. The methodology involves data acquisition through high-speed uni-axial compression tests, preprocessing, empirical curve fitting, and model training. The performance of the trained CANN is evaluated against experimental results and compared with existing analytical and numerical methods.
Results show that the CANN model accurately captures the stress-strain response of FRPs across varying strain rates. By incorporating physics-based constraints, the model improves extrapolation beyond the training data. These findings demonstrate that CANNs offer a viable and computationally efficient alternative for predicting strain-rate-dependent behavior in FRPs, with potential applications to full the gap of material behavior for simulations, crashworthiness analysis, and material design
