Research On Lamb Wave Acquisition And Damage Detection System Using Optical Low Coherence Technology

With the continuous progress and development of science and technology, many industrys havemore and more highly requrement for materials.The application environment of materials andstructures are more badly, such as applied to wind turbine blades and aircraft and space vehicles.Their composition has become increasingly complex, there are more and more potential safety hazard,damage detection of materials are becoming increasingly important.Guided wave technology has been proved to be a very effective and practical method of materialdamage detection. As a typical guided wave signal, Lamb wave has been widely used in the detectionof many plates structures,very suitable for large-area plate material.For overcome traditionalpiezotransducers are vulnerable to electromagnetic interference and cannot detect in real time for along time.An optical fiber sensor measure the feeble vibration produced by Lamb wave propagated onthe surface of a solid plate based on optical low-coherence in this paper, building Lamb wavedetection system based on optical low-coherence technology, achieveing optical non-contact scanningdetection for the Lamb wave.A measurement system based on the optical low-coherence method that using piezoelectricelements as actuators to detect the Lamb wave was constructed. We are respectively exert to differentfrequency of sine wave excitation signal and a windowed sinusoidal excitation signal in experiment,indicating that the damage detection system of the Lamb wave is feasible. Through the method ofpeak arrival time to measure Lamb wave propagation velocity in experiment, and for comparison withtheoretical velocity through the Rayleigh-Lamb frequency equation, the experimental velocity isconsistent with the theoretical velocity.Two experiments show that the measurement system of opticallow-coherence can accurately detect the Lamb wave signal.Lamb wave detection software system based on optical low-coherence method was designed tocontrol stepping motor，achieveing optical fiber to scan the damage of aluminum plate. A10mmdiameter of round orifice in specimen was qualitative judged by using the power spectral densitydifferences and damage factor. The location of damage was quantified determined by using ovalpositioning method, which measuring error was1.5cm.The experimental results show that the Lambwave detection system can successfully locate the damage of the material.