Publications

Results 2126–2150 of 96,771

Search results

Jump to search filters

Extinction Imaging Diagnostics for In Situ Quantification of Soot within Explosively Generated Fireballs

Propellants, Explosives, Pyrotechnics

Saltzman, Ashley J.; Brown, Alex; Wan, Kevin W.; Manin, Julien L.; Pickett, Lyle M.; Welliver, Marc W.; Guildenbecher, Daniel R.

Fireballs produced from the detonation of high explosives often contain particulates primarily composed of various phases of carbon soot. The transport and concentration of these particulates is of interest for model validation and emission characterization. This work proposes ultra-high-speed imaging techniques to observe a fireball's structure and optical depth. An extinction-based diagnostic applied at two wavelengths indicates that extinction scales inversely with wavelength, consistent with particles in the Rayleigh limit and dimensionless extinction coefficients which are independent of wavelength. Within current confidence bounds, the extinction-derived soot mass concentrations agree with expectations based upon literature reported soot yields. Results also identify areas of high uncertainty where additional work is recommended.

More Details
TYPE Journal Article YEAR 2023
DOIOSTIScopus

Multi-fidelity microstructure-induced uncertainty quantification by advanced Monte Carlo methods

Materialia

Laros, James H.; Robbe, Pieterjan; Lim, Hojun L.

Quantifying uncertainty associated with the microstructure variation of a material can be a computationally daunting task, especially when dealing with advanced constitutive models and fine mesh resolutions in the crystal plasticity finite element method (CPFEM). Numerous studies have been conducted regarding the sensitivity of material properties and performance to the mesh resolution and choice of constitutive model. However, a unified approach that accounts for various fidelity parameters, such as mesh resolutions, integration time-steps and constitutive models simultaneously is currently lacking. This paper proposes a novel uncertainty quantification (UQ) approach for computing the properties and performance of homogenized materials using CPFEM, that exploits a hierarchy of approximations with different levels of fidelity. In particular, we illustrate how multi-level sampling methods, such as multi-level Monte Carlo (MLMC) and multi-index Monte Carlo (MIMC), can be applied to assess the impact of variations in the microstructure of polycrystalline materials on the predictions of homogenized materials properties. We show that by adaptively exploiting the fidelity hierarchy, we can significantly reduce the number of microstructures required to reach a certain prescribed accuracy. Finally, we show how our approach can be extended to a multi-fidelity framework, where we allow the underlying constitutive model to be chosen from either a phenomenological plasticity model or a dislocation-density-based model.

More Details
TYPE Journal Article YEAR 2023
DOIOSTIScopus
Results 2126–2150 of 96,771
Results 2126–2150 of 96,771