Research On Corrosion And Fatigue Damage Monitoring Of Steel Wire Based On Piezoelectric Ceramics Transducers

With the improvement of China’s comprehensive strength and the increasing demand for transportation,the bridge structure is also developing towards a larger span.The long-span bridges mostly use cables as the main force members.Long-term in a complex environment and withstand fatigue loads,the steel wire inside the bridge cable is prone to corrosion,and the fatigue performance of the steel wire after corrosion will be greatly reduced.The resulting cable breakage and even bridge collapse accidents are not uncommon.Therefore,it is of great significance to develop a monitoring method for the corrosion of bridge cables and the corresponding damage evaluation indicators.In recent years,piezoelectric monitoring technology has been widely used in structural health monitoring.Among them,piezoelectric ceramics have the advantages of low price and flexible layout,and are very suitable for being arranged in bridge cable structures.In this paper,based on the common rust and post-rust fatigue problems of parallel cable,a high-strength steel wire rust fatigue damage monitoring method based on piezoelectric ceramics is proposed.Based on the traditional piezoelectric signal analysis,the frequency band variation based on wavelet packet energy spectrum is introduced.The damage evaluation index was carried out,and the parallel steel wire corrosion and rust post-wire bundle fatigue monitoring test was carried out to verify the feasibility of the monitoring method and damage index.The specific research work is as follows:(1)A damage evaluation index based on the energy band energy variation of the wavelet packet energy spectrum is introduced.In order to obtain better noise robustness and damage sensitivity,the wavelet packet energy spectrum of the signal is obtained by wavelet packet decomposition,and the energy band of the larger frequency band is selected to form the characteristic frequency band,and the characteristic band energy and all frequency bands are adopted.The change of the average value of the energy is used as the early warning parameter,and based on this,the damage evaluation index of the energy ratio variation deviation and the variance is established.(2)Developed piezoelectric guided wave monitoring technology for high strength steel wire corrosion.Accelerate the corrosion of the high-strength steel wire by a steady-current power supply,paste the PZT on the two end surfaces of the high-strength steel wire,use the frequency sweep signal to stimulate the PZT at one end,and perform signal acquisition at a certain interval.The test results show that with the increase of the degree of corrosion of high-strength steel wires,the time-domain signal,frequency-domain signal,and wavelet packet energy will be significantly attenuated.Especially during the galvanization of the steel wire,the signal decays faster.The damage index of steel wire corrosion based on wavelet packet energy spectrum increases linearly with the increase of the corrosion degree,and the damage indexes ERVD and ERVV both have better anti-noise ability.When the signal-to-noise ratio reaches 10db,the sensitivity index K of the damage index ERVD only decreases by 3.03%.Under the strong noise environment of 0db,the K value can still reach 0.0475;the damage index ERVV has a higher degree of fitting,and the strong noise at 0db The environment still reached 0.9273.(3)A method for fatigue damage monitoring of corroded steel wire bundles based on piezoelectric guided waves was proposed.Fatigue tests for steel wire bundles with different rust rates were designed.PZT was attached to the two ends of the steel wire as transmitting and receiving sensors.The steel wire was monitored by piezoelectric guided waves after a certain number of fatigue times.The test results show that the energy attenuation of piezoelectric signals can effectively reflect the three processes of steel wire fatigue damage.There is no fatigue crack on the uncorroded steel wire,and the corresponding piezoelectric signal does not change much.The fatigue performance of the rusted steel wire is greatly reduced.After the fatigue crack occurs,the piezoelectric signal decays with the increase of the number of fatigue.When the fatigue limit of the wire is approached,the wavelet packet of the signal The degree of energy attenuation increases,and the closer the signal acquisition time is to the fatigue limit,the more severe the signal attenuation.The damage index based on wavelet packet energy spectrum increases with the degree of fatigue damage,which can effectively reflect the degree of fatigue damage of steel wires.