| Railway turnout switch rail (including long point rail) which plays an important role of guiding the locomotive line, is one of the key points which influence the safety of maintenance equipment. With the rapid development of China's railway industry, train speed and traffic volume is correspondingly increased, and the switch rail damage trend is increasing. How early detection switch rail damage can be detected and ensuring the safety of railway transportation, is becoming new topic of the railway nondestructive testing. Guided wave detection technology has the advantage of one-stimulating, large area and long distance detection, and the structural health monitoring (SHM) can be realized. It's expected to be used in rail switch rail parts (including long point rail) nondestructive detection.The research status based on guided wave detection technology at home and abroad is summarized at first. And based on a summary of the guided wave of classic theory and practical application, the method of detecting switch rail of guided wave principle and feasibility are studied, which summarized the guided wave detection technology at home and abroad including research status and development trend. The commonly used analytical method and numerical method for the guided wave propagation mechanism analysis are compared, and the advantages of the characteristics of various methods are listed. The limitations of the commonly used methods are also listed. Excitation of guided wave structure analysis is done, and high heat of guided wave wavelet transform, empirical mode decomposition and frequency domain signal processing techniques are discussed in detail; The research results of wave propagation the researchers at home and abroad ultrasound on the guide rail and turnout are summarized and analyzed.Based on Navier control equation,60 type rail and its switch rail parts of the rail bottom, rail waist, rail head is approximately dealt as slab waveguide with different thickness. The rail bottom, rail waist, railhead in critical thickness of symmetric and against mode,whose Rayleigh lamb frequency dispersion equations are deducted. The critical thickness of the phase velocity dispersion curve, group velocity dispersion dispersion curve, excitation angle curve of rail are programmed and drawn. And the best Lamb wave excitation frequency and excitation angle of rail and its each switch rail parts are studied.Using finite element theory, guided wave propagation characteristics in the switch rails are studied. The local switch long core rail 3D entity model is established.The damage modeling and finite element analysis and solving of the sound field of the switch rail are carried on.The study of guided wave frequency dispersion relation and propagation characteristics is done. Simulation is done using transient dynamics module, with hexahedral elements, choosing Hanning window amplitude modulated sinusoidal signal as excitation.The rail base excitation and the rail waist excitation wave field snapshots are obtained respectively, and the defect echo time is calculated. The defect of precise positioning can be obtained.Based on the principle of the interference of polarized light, the elastic field dynamic optical imaging system is built, and the bottom of the switch rail and rail waist variable cross-section optical test block with K9 optical glass material are designed and produced. Choosing different probes, research of different probes to excite guided wave in the test block in the sound field is carried on. Using CCD shooting test block, guided wave sound field images through the computer software are taken for acquisition and analysis. The sound field visualization is implemented.In this paper, two sets of guide wave transmitting and receiving system based on excitation and arbitrary waveform pulse excitation are built. And different types of probe, different excitation frequency and excitation angle probe trial block excitation of guided wave propagation characteristics in the switch rail are all studied. The artificial defects with different size in the switch rail and long core rail are made to study the guide wave's detectability of the switch rail defects.The research of guided wave emission receiving system which collects the data of time-frequency domain signal is processed. The wavelet packet transform is used in signal denoising. Wavelet packet energy spectral energy distribution is dealt as a basis for judging the defects of switch rails. The wavelet frequency analysis method is used to analyze the guided wave signal's instantaneous frequency. The HHT time frequency analysis method was used in the analysis and processing of signal detection. The IMF is decomposed by EMD for signal reconstruction, and the envelope of the signal reconstruction spectrum is extracted.The groove defects can be precisely positioned. |
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