Numerical study on the excitation-dependent nonlinear behavior of distributed microcracks
Loading...
Author(s)
Goletz, Marius
Advisor(s)
Editor(s)
Collections
Supplementary to:
Permanent Link
Abstract
Since it is well known that microcracks generate higher harmonics in propagating monochromatic waves, there exist dfferent approaches to model this phenomenon. Recent research from Hoffmann et al. combined a Bilinear Stiffness model and a Rough Surface Contact model for a more complete description of the nonlinear behavior
of materials containing distributed microcracks. This model intends to be
utilized to simulate second harmonic generation in dependence of characteristic crack parameters, e.g. crack radius and number of cracks. The materials considered in this context are Nanostructured ferritic alloys (NFA). This research presents a numerical approach to determine this dependency, since
other methods like the pertubation method fail due to the strong nonlinear effects occurring in such materials. In the first instance, the problem is formulated as a hyperbolic system of conservation laws, before it is implemented and solved with a semi-discrete central scheme. The numerical results are then studied using the signalprocessing tool fast Fourier transform (FFT) in order to analyse and interpret the nonlinear effects. To ensure on the one hand, that numerical algorithm works properly and on the other hand, to understand and interpret the results, the problem is approached step by step. After validating the numerical scheme for a linear problem,
only the quadratic part of the combined model is examined for varying crack parameters. In a next step, the full model is investigated for different crack parameters. This procedure allows to better understand the evolution and physical interpretation of the strong nonlinear effect observed when the full model is considered.
Sponsor
Date
2019-09-03
Extent
Resource Type
Text
Resource Subtype
Thesis