Signal processing for the guided wave test based on the empirical mode decomposition

In order to detect the small defect, the empirical mode decomposition (EMD) method is employed to process the magnetostrictive guided wave testing signal. Firstly, the principle of the EMD is introduced. Then, the experimental setup is developed to obtain guided wave testing signals. Both the prestressing strand and the parallel wire cable have been manufactured grooves in the wires. It is difficult to find the defect signal from the original signal. By means of the EMD, the test signal is decomposed into series of the intrinsic mode functions (IMFs). The small defect signal is enhanced by analyzing the different order of the IMF. It is easy to find the small defect signal in the first mode wave for the prestressing strand. For the parallel wire cables, the second and third mode can be used to find the small defect signal. These test results indicate that the EMD approach can suppress noise effectively and improve the ability of guided wave testing of the small defect.