Application of giant magnetic impedance in bridge detection

2022-05-30 0 By

The bridge above was discussed a few days ago, it is said that it is still closed, after all the cable fell, think of the consequences.Nothing happened these days. I talked to my colleagues about this matter. Especially, even though the bridge was opened to traffic after repair, I couldn’t relax at all on the inspection and monitoring of the bridge and the inspection and maintenance of the rod and cable.Our colleague Yang Donghao, Yang Gao Gong, has something to say. Let’s listen to the application of giant magnetic impedance in bridge maintenance and rod and cable detection.Of course, the most important thing is: we already have the corresponding product in the actual work, the upgraded version is on the way!A recently, bridge wire fracture fall off somewhere in shanxi incident has caused quite a concern within the transportation sector, as the chart shows, from road bridge connection of the lateral meniscus shape a suspension wire, steel structure of the fracture to fall from the sky falling in the road, as a result, pulled the lateral wire number of large steel structure bridge less a root,The south Central Bridge was temporarily closed to ensure the safety of vehicles. Fortunately, there were no casualties, but the incident is a wake-up call for operators of similar Bridges of similar design and structure.As a kind of cable system, cable stayed bridge has greater span capacity than beam bridge and is the most important bridge type of long-span bridge.Cable-stayed bridge consists of many cables directly connected to the tower to lift the deck, cable-stayed bridge is mainly composed of cable tower, main beam, stay cable.Cable-stayed bridge structure belongs to high order statically indeterminate structure in mechanics, which is the most complex structure in all bridge types.Because of the different cable forces and construction methods, the final stress state of the bridge will be obviously different.Therefore, in the force analysis of cable-stayed bridge structure, the primary task is to determine the reasonable bridge state, so as to make the bridge structure uniform force, and then determine the reasonable construction state.It can be seen from the figure that the vertical curve of cable-stayed bridge has a great influence on the stress of the main girder. Therefore, the calculation axis of the main girder must be established according to the vertical curve in the modeling of cable-stayed bridge.Capture the cable on cable-stayed bridge on the load-bearing capacity of support play a crucial role, based on this we are carried out, in the construction of the bridge under construction and maintenance, should focus on the “health” of wire rope, its security is directly related to the normal operation of the bridge and the use of staff’s life safety, steel wire rope in many areas is mandatory testing project,For example, in the elevator, wire rope detection is one of the mandatory testing items, the need for regular testing and maintenance.Wire rope detection has visual method, acoustic emission, ultrasonic, resistance method and magnetic leakage detection methods, with the continuous progress of magnetic material technology, now there is a new technology to solve the bridge detection, based on cobalt amorphous wire giant magnetic impedance effect multi-feature characterization method to detect Bridges.Giant magnetic impedance (GMI) refers to the phenomenon that the AC impedance of a material changes significantly with the applied magnetic field.Since the Giant magneto-impedance GMI effect was found in cobalt-based amorphous wires by Japanese researchers in 1992, the GMI effect has attracted wide attention and research in the world.The GMI magnetic sensor based on this effect has obvious advantages in sensitivity, stability, response speed, power consumption and sensor size, and has good adaptability and wide application prospect.The skin effect of sensitive materials under high frequency excitation is used to analyze the mechanism of GMI effect.Skin effect refers to the uneven distribution of current on the cross-sectional area of the conductor when the alternating current passes through the conductor. The closer it is to the surface of the conductor, the greater its current density, mainly caused by the induction of current.The skin effect formula is: in the screenshot, ρ is the resistivity of the sensitive material;F is the frequency of the excitation signal;μφ is the circular permeability;The physical meaning of δ can be understood as the distance from the conductor surface when the current density inside the conductor is 37% of the current density on the conductor surface.Based on this formula, we can extend thinking application in bridge wire, the magnetic array detection technology, by a type of GMI multichannel ultra high sensitivity gradient sensors, load carrier robot climbing rope, movement type of real-time characteristics of magnetic anomaly extraction, recognition and judgment, real-time detect all kinds of flaws of the internal steel wire rope, accurate positioning defect position.The above test curve is a multi-feature characterization method for GMI effect. Through comparative test analysis, this characterization method can overcome the limitation of single feature characterization method and improve the measurement accuracy while expanding the measurement range.Compared with the traditional cable flaw detection technology, the application of GIANT magnetic impedance flaw detection technology has the advantages of high sensitivity, accurate flaw detection location, fast detection speed and so on, which is a cost-effective detection technology.In the comparison of detection efficiency between large and extra-large cable-stayed Bridges, GMR technology can improve detection efficiency by 3 orders of magnitude, and the operation process is simple, and a single person can complete the whole process of detection, which has been successfully applied in a bridge cable detection in Jiangxi province.With the mature application of this technology in bridge design, construction and operation and maintenance, it will significantly improve the “health level” of Bridges, and provide an important boost to the quality and efficiency of social development and economic construction.Screenshots — E N D — Text: Dong Hao, Yingwu Illustration: Network