Development And Application Of Multi-channel Guided Wave Focusing Detection System

With the rapid development of guided wave detection technology in the field of non-destructive testing,various new detection methods based on guided wave technology continue to emerge.Among them,the use of sensor arrays combined with the characteristics of guided waves can achieve wide-range high-precision defect detection,which can be widely used in non-destructive testing of industrial plates and pipes.According to the application requirements of guided wave focusing detection technology,a multi-channel guided wave focusing detection system is developed in this dissertation.Combining the piezoelectric sensor array and guided wave detection technology,the focusing detection of defects on plate structures and pipes are employed,which effectively improves the detection sensitivity of small defects.In addition,focusing imaging of defects is implemented.The main contents of this dissertation are shown as follows:(1)A multi-channel guided wave focusing detection system is developed.The research is carried out from the aspects of overall system design,modularized hardware circuit design,programming,system functional test,and software design on the host computer.It realizes the excitation of 16-channel guided wave signals and the synchronous acquisition of 16-channel signals.Using FPGA(Field Programmable Gate Array)as the main control unit of the excitation and acquisition module,generation of tone-burst signals based on DDS(Direct Digital Synthesis)technology and highvoltage amplification of excitation signals by high-voltage power amplifier(PA85)are realized.Each excitation channel is independent of each other and its parameters are adjustable,with the function of simultaneous excitation and delayed excitation.16-channel signal acquisition module possesses high-voltage limit protection,programcontrolled gain,and filtering function.It can realize the automatic collection and storage of full matrix data through the host computer program.(2)Research on defect focusing detection and imaging of plate structure is carried out.Taking a 1mm thick aluminum plate as an example,phased focusing detection is implemented for defects at different positions,based on a linear piezoelectric sensor array,both through finite element simulation analysis and experimental research by the developed multi-channel guided wave focus detection system.It improves the ability of guided waves in detecting defects.Total focusing imaging algorithm is employed to realize the location and imaging of multiple defects.The amplitude total focusing imaging method is combined with the sign coherence factor imaging method,and the results show that the composite total focusing imaging method optimizes the amplitude total focusing results and greatly improves the imaging quality.(3)Research on defect focusing detection and imaging of pipes is also carried out.Taking a wall thickness of 5mm pipe as a target.The finite element simulation analyzes and optimizes the phased focusing detection methodology by L(0,2)mode of the guided waves in the hollow pipe.Different types of defects are located and imaged,and direction control of excited guided waves were realized.