Simulations of ultrasonic guided wave identification using a chaotic oscillator

A novel inspection method of ultrasonic guided waves was proposed here based on the improved Duffing chaotic oscillator with substitution of(-x~3 + x~5)for(-x+x~3) of the non-linear restoring force item.Firstly,the effects of frequency and damping ratio on the chaotic systems were studied using Melnikov's method.Based on this,the frequency of the force and the damping ratio could be determined considering the frequency of the detected signal and noise level, respectively.The chaotic system could transfer the phase from a quasi-periodic motion to chaotic motion with double attractors by changing the amplitude of the driving force.And then,the statistical properties of the noise effect on the system were discussed in detail.It was obviously different from the non-balance phase transition of the system,inducing a chaotic motion with double attractors when inputting a guided wave signal but only inducing a disturbance when inputting a pure noise.Furthermore,a dichotomy was suggested to locate the time of the guided wave.And the effect of the guided wave length on the phase map was studied in detail.The simulations showed the higher sensitivity of the system to the guided wave and its stronger immunity to noise.It was shown that the presented method can be used to inspect weaker guided waves,to extend their detection range and to increase the sensitivity of detecting micro-defects.