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Конференции
Описание
Imaging techniques such as EUSR or Excitelet algorithms used in guided wave damage detection rely on an accurate knowledge of group or phase velocities. The problem is that variability in material properties directly affects the guided wave dispersion curves. Traditional approaches to mechanical characterization are based on ASTM standards. However, most of these techniques require numerous specimens to test and evaluate the properties of a structure within a few percents. The main goal of this paper is to assess a new integrated characterization approach to identify the mechanical properties of an isotropic structure (Young's modulus, Poisson's ratio, density) onto which imaging is performed to detect damage. The integrated characterization approach is based on a modified version of the Excitelet algorithm, where mechanical properties, instead of geometrical features, are set as the variables to be identified. This paper thus aims at evaluating the benefit of using the same array of transducers, and similar signal processing tools, to first identify the mechanical properties of the structure using a modified version of the Excitelet algorithm and then produce an image of this structure using the standard Excitelet imaging algorithm. The experimental setup consists of an aluminum plate with a 2 mm notched hole and instrumented with a linear array of seven circular elements micro-machined from bulk piezoceramic (PZT). Excitelet imaging is performed with the linear array and the characterization uses this same array and an extra PZT transducer located in the near field of the array. In this paper, low order Lamb modes are exploited for both characterization and imaging techniques. The results obtained for the properties identified with the modified Excitelet algorithm are within 1% of properties from the material supplier. Imaging results are then presented using Excitelet with both A0 and S„ modes at dispersive frequencies for the localization the notch. This integrated characterization algorithm combined with the Excitelet imaging technique is shown to improve the accuracy of the localization of the damage for isotropic structures.
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25 декабря 2013
09 января 2014
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