Study On Structural Nonlinear Damage Identification Method Based On Time-Domain Coherence Function And Volterra-Wiener Model

At present,thanks to the rapid development of modern science and technology,the level of sensing technology,signal acquisition technology,and data processing technology has been greatly improved.In the field of structural health detection,structural damage identification has received more and more attention.In a structural system with nonlinear behavior,because the nonlinear behavior may be mixed with damage,the problem of structural health detection is more complicated.Currently,a variety of technologies have been developed to detect different types of structural damage.Affected by the environment and various sudden factors,the structure often has structural damage problems such as cracks,corrosion,and material aging,and these problems often have some safety hazards.In order to avoid safety accidents caused by structural damage and ensure the long-term operation of the structure,the research on structural damage detection is particularly important.This paper adopts a linear and nonlinear structural damage identification method based on time-domain coherence function.Using the peak coherence function,two new damage indexes are constructed,and detailed numerical research is carried out on the spring damping mass system.The results show that these two indicators are very sensitive to linear and non-linear structural damage,and they can accurately identify the damage even under severe noise-contaminated signals.In order to eliminate the influence of spectrum distribution,a new analysis mode decomposition method is used to extract signals in specific frequency bands for short-time time-domain coherence analysis.Experimental results show that indicators constructed by time-varying functions are more sensitive to structural damage than indicators constructed by a single deterministic parameter,especially for weaker stiffness damage and strong nonlinearity.This paper adopts a nonlinear system identification method based on time series Volterra-Wiener model.The aluminum cantilever beam test model is selected,the electromagnetic exciter is used to apply simple harmonic excitation,and the displacement signal is picked up by the sensor.By changing the damage near the structural support,using white noise excitation to identify the kernel function of the system before and after the damage;The kernel function is used as the basic feature quantity to carry out the coherence analysis,the statistical parameters of the coherence analysis are used to construct the damage discrimination index,and the damage result identification is carried out by the threshold method and the statistical method.The experimental results show that the threshold method can use the kernel function obtained by the damage structure identification and the benchmark kernel function to analyze the coherence,and construct the index to identify the damage.Although the calculation efficiency is high,the sensitivity of identifying small damage is very low,and it is easy to cause Missing judgment;the statistical method uses the coherence analysis between the kernel function identified by multiple tests and the benchmark kernel function,and performs statistical analysis,and uses the probability density function of the peak coherence function characteristic index and its statistical index to perform damage identification,although the test The sum of calculation is relatively large,but it can more accurately and sensitively identify the occurrence of damage.In practical applications,it can be selected according to actual engineering conditions,or comprehensively judged by multiple indicators.The innovation of this paper is to adopt the short-term time-domain coherence analysis method and the time series Volterra-Wiener model to construct the damage identification indicators respectively,and improve the identification results on the basis of the predecessors,and achieve the expected results.