238 research outputs found
Micromechanical fatigue experiments for validation of microstructure-sensitive fatigue simulation models
Crack initiation governs high cycle fatigue life and is sensitive to microstructural details. While corresponding microstructure-sensitive models are available, their validation is difficult. We propose a validation framework where a fatigue test is mimicked in a sub-modeling simulation by embedding the measured microstructure into the specimen geometry and adopting an approximation of the experimental boundary conditions. Exemplary, a phenomenological crystal plasticity model was applied to predict deformation in ferritic steel (EN1.4003). Hotspots in commonly used fatigue indicator parameter maps are compared with damage segmented from micrographs. Along with the data, the framework is published for benchmarking future micromechanical fatigue models
Micromechanical fatigue experiments for validation of microstructure-sensitive fatigue simulation models
Crack initiation governs high cycle fatigue life and is sensitive to microstructural details. While corresponding microstructure-sensitive models are available, their validation is difficult. We propose a validation framework where a fatigue test is mimicked in a sub-modeling simulation by embedding the measured microstructure into the specimen geometry and adopting an approximation of the experimental boundary conditions. Exemplary, a phenomenological crystal plasticity model was applied to predict deformation in ferritic steel (EN1.4003). Hotspots in commonly used fatigue indicator parameter maps are compared with damage segmented from micrographs. Along with the data, the framework is published for benchmarking future micromechanical fatigue models
Microbunching instability characterization via temporally modulated laser pulses
High-brightness electron bunches, such as those generated and accelerated in
free-electron lasers (FELs), can develop small-scale structure in the
longitudinal phase space. This causes variations in the slice energy spread and
current profile of the bunch which then undergo amplification, in an effect
known as the microbunching instability. By imposing energy spread modulations
on the bunch in the low-energy section of an accelerator, using an undulator
and a modulated laser pulse in the centre of a dispersive chicane, it is
possible tomanipulate the bunch longitudinal phase space. This allows for the
control and study of the instability in unprecedented detail. We report
measurements and analysis of such modulated electron bunches in the
2Dspectro-temporal domain at the FERMI FEL, for three different bunch
compression schemes. We also perform corresponding simulations of these
experiments and show that the codes are indeed able to reproduce the
measurements across a wide spectral range. This detailed experimental
verification of the ability of codes to capture the essential beam dynamics of
the microbunching instability will benefit the design and performance of future
FELs
Microbunching instability characterization via temporally modulated laser pulses
High-brightness electron bunches, such as those generated and accelerated in free-electron lasers (FELs), can develop small-scale structure in the longitudinal phase space. This causes variations in the slice energy spread and current profile of the bunch which then undergo amplification, in an effect known as the microbunching instability. By imposing energy spread modulations on the bunch in the low-energy section of an accelerator, using an undulator and a modulated laser pulse in the center of a dispersive chicane, it is possible to manipulate the bunch longitudinal phase space. This allows for the control and study of the instability in unprecedented detail. We report measurements and analysis of such modulated electron bunches in the 2D spectrotemporal domain at the Fermi FEL, for three different bunch compression schemes. We also perform corresponding simulations of these experiments and show that the codes are indeed able to reproduce the measurements across a wide spectral range. This detailed experimental verification of the ability of codes to capture the essential beam dynamics of the microbunching instability will benefit the design and performance of future FELs
- …