| Engineering structure is the key part to carry the weight of equipment and realize the load transfer.The safety and reliability of the structure is a very important index in the engineering practical application stage.However,due to the influence of alternating load,environmental erosion and other factors in the service process,damage will inevitably occur in the structure,leading to structural strength and performance degradation,which may cause economic losses or even casualties in serious cases.Therefore,it is of great significance to carry out the research on structural health monitoring damage identification system.Compared with other detection technologies,ultrasonic guided wave detection technology is widely used in the field of structural health monitoring due to its advantages of long propagation distance,fast detection speed and high sensitivity.Aiming at the needs of damage identification in engineering structures,this paper designs a multi-channel,wide-band,high-precision and high-reliability ultrasonic guided wave active structural health monitoring system.The main research contents include:(1)Principle and scheme design of ultrasonic guided wave monitoring system.Firstly,the propagation characteristics of ultrasonic guided waves were analyzed theoretically,the multi-mode characteristics and dispersion characteristics of Lamb waves were analyzed and derived,and the energy conversion mode of piezoelectric effect was analyzed.The piezoelectric ceramic transducer was used as the sensor to stimulate and receive ultrasonic guided waves.From the perspective of overall design,aiming at the problems existing in the engineering application of ultrasonic guided wave monitoring system,the functional design requirements of ultrasonic guided wave monitoring system are summarized,and the performance index parameters are formulated.On this basis,the overall design scheme of the system hardware and software is formulated.(2)Hardware design of ultrasonic guided wave monitoring system.In order to adapt to the complexity of the structure to be tested,a multi-sensor integrated sensing intelligent layer is designed as the sensor network.Based on the overall design scheme of ultrasonic guided wave monitoring system and the requirements of performance index,a system host composed of signal generation module,power amplifier module,channel switching module,signal conditioning module,data acquisition module,collaborative control module and power module is developed.According to the requirements of the system,the selection and design of each part of the circuit are completed.DDS technology is used to realize the rapid synthesis of the excitation signal,the power amplifier circuit and the transformer booster circuit are used to realize the high power drive,the electronic switch chip is used to realize the switching of the excitation receiving channel and the cross talk suppression,and the high-precision adjustable gain operational amplifier is used to realize the weak signal amplification.Dual-channel high-speed acquisition circuit is adopted to realize data acquisition,and multi-controller cooperative mode is adopted to realize the underlying logic control.(3)Software design of ultrasonic guided wave monitoring system.Write the lower computer software program of multi-controller collaborative control management,mainly responsible for driving the system hardware,coordinating the control logic between different operations,carrying out data transmission and timing control of the system,and realizing data transmission,signal generation,data acquisition,channel switching,signal conditioning and other functions.The upper computer software integrates damage imaging algorithm,mainly including hardware management,sensor network configuration,signal preprocessing,damage location analysis and data management modules,with automatic sensor network construction,digital processing of sampled signals,real-time display of response waveform,automatic damage location imaging and other functions.(4)Test and analysis of ultrasonic guided wave monitoring system.A test platform was built for the ultrasonic guided wave monitoring system designed in this paper,and the hardware performance,positioning accuracy and reliability of the system in complex environment were tested.First of all,the system performance is verified to verify that the system has good excitation signal output and response signal acquisition function within the bandwidth range and the high-speed switch has the ability to truncate crosstalk.On this basis,the positioning experiment of the system is carried out through the composite material plate.The results show that the designed system can identify the damage and locate the system accurately,and the positioning error is less than 6.7mm.Finally,the reliability of the system host is tested,and the test results show that the system can work stably under complex environment.In this paper,an ultrasonic guided wave monitoring system integrating sensing intelligent layer,system host and upper computer software is developed to meet the actual engineering requirements,and experiments are carried out to test the system’s performance indicators,damage location effect and reliability.The developed ultrasonic guided wave monitoring system has good stability and environmental adaptability,and has obvious advantages in positioning accuracy and complex environment,which provides a solution for damage detection of engineering structures under complex working conditions. |
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