A detection method of nonlinear ultrasonic guided wave with carrier modulation

A detection method of nonlinear ultrasonic guided wave with carrier modulation is characterized in that the method comprises the following steps:

• Step S1:
• The high and low frequency components are determined according to the frequency response characteristics of the detection object, and the high-frequency components are processed by delay and combined with the low-frequency components to form a carrier modulation signal;
• Step S2:
• The single excitation and single receiving mode are adopted for signal acquisition, the carrier modulation signal with high frequency and low frequency components is excited by a single transducer, the nonlinear modulation effect is produced by the interaction between the carrier signal and the damage, and the signals are collected by the receiving transducer through transmission method;
• Step S3:
• According to the arrival time of high frequency components and the time of end reflection echo, the signal is intercepted and analyzed, after filtering and normalization processing, the received signal is decomposed by empirical mode decomposition (EMD), according to the decomposed IMF spectrum information, IMF components including fundamental frequency and nonlinear frequency components are used for signal reconstruction;
• Step S4:
• The difference frequency components generated by the modulation of high-frequency and low-frequency, namely nonlinear components, are extracted, and the non-linear coefficient is calculated, the damage degree of materials is evaluated based on the nonlinear coefficient of nondamaged state.