The Selection of Optimal Mode Pair of Nonlinear Guided Waves in Waveguide of Arbitrary Cross-section

The existing researches have indicated the conditions that mode pair of fundamental mode and second harmonic mode need to satisfy to produce the cumulative second harmonic. However, due to the multimodal characteristics of ultrasonic guided waves, the conditions are very complex. In this article, a numerical simulation method is proposed to select the optimal mode pair that can generate the cumulative second harmonic mode with the largest amplitude in waveguide of arbitrary cross-section. The optimal mode pair is determined by calculating and comparing the amplitude coefficients of different mode pairs based on mode shape analysis. The CHN60 rail is taken as an example for simulation verification, and the optimal mode pair of nonlinear guided waves in rail is selected.