Development of fidelity criteria for finite element modeling of thick cylindrical waveguides

摘要

Measurement of the time delay between axially symmetric waves for the first and second arrival in a thick cylindrical waveguide is well established to determine the shear and Young's modulus of a material. The use of cylindrical buffer rods is used to determine the modulus of materials at elevated temperatures. The use of this method is described in classic references in the area [1] as well as in more recent papers [2]. The modulus of the material is determined based on the delay between waveguide modes. The normal method employed is to measure the time delay between the peaks using pulse overlap or crosscorrelation approaches. The resulting measurement is the difference in the average group delay between the modes. Experimental errors related to dispersion of the signal control the accuracy of the measurement. Other applications for solid cylindrical waveguides include process monitoring [3] and smart structures [4]. In these applications the diameter of the waveguide and the frequency of the input signal require the waveguide be modeled as a thick cylinder.