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Influence of the correlation lengths on the continuous mode conversion
Author(s) -
Zimmmermann Eugen,
Weber Wolfgang
Publication year - 2021
Publication title -
pamm
Language(s) - English
Resource type - Journals
ISSN - 1617-7061
DOI - 10.1002/pamm.202000245
Subject(s) - covariance , covariance function , mode (computer interface) , random field , antisymmetric relation , modal , mechanics , statistical physics , materials science , physics , mathematics , composite material , computer science , statistics , mathematical physics , operating system
To detect damages using guided waves, the local mode conversion of a symmetric S0 mode into an antisymmetric A0 mode can be utilized. In simulations which use a homogeneous material model, the conversion will take place only at structural irregularities, e.g. damages. In contrast, the wave propagation in carbon reinforced plastics (CFRP) is more complex. Due to the irregular arrangement of the fibres, regions with varying fibre volume fraction are present. This spatial fluctuation causes an inhomogeneous material behaviour, which significantly influences the wave propagation. In addition to the primary induced symmetric S0 waves, secondary A0‐waves arise which are caused by the material itself and extends over the entire structure, they are continuous. These are also present if the structure is intact and consequently makes it more difficult to detect damage. In order to include the spatial variation of the material properties in the numerical model, second order random fields, which are fully represented by their mean and covariance, can be used. The random distribution of the material properties over a region can be achieved by Karhunen‐Loève decomposition. The spatial structure of the decomposition and therefore the random field depend on the chosen covariance function.