Development Of Concrete Ultrasonic Tomography Instrument

As the preferred material for modern infrastructure construction,the structural strength of concrete buildings is closely related to the safety of people's life and property.The two key factors that determine the performance of concrete detector are the accuracy of data acquisition system and the reliability of data processing and imaging algorithm.Therefore,the development of the concrete ultrasonic tomography detector will be carried out from these two aspects.The data acquisition system of the concrete ultrasonic tomography detector users TEXAS INSTRUMENTS 16 bit analog-to-digital conversion chip ADS1605 with a maximum sampling frequency of 10 MHz as the core component of the system.In order to ensure the accuracy and sensitivity of analog-to-digital conversion,a signal conditioning circuit composed of two low-distortion,all-difference amplifier ada4940-1 and a variable gain amplifier AD8338 is designed at the input end of the analog-to-digital conversion circuit to amplify and filter the signals received by the ultrasonic probe.The control of the whole acquisition system is realized by FPGA.Specifically,the sampling controller and FIFO interface are designed by Verilog hardware description language,and connected to FPGA soft core Nios II through Avalon bus.In addition,considering the reliability of data transmission and the improvement of transmission speed,data is buffered by FIFO in FPGA and transferred to SDRAM by DMA.Data processing and imaging algorithm is composed of S5P6818 as the core ARM processor equipped with Android system,including Android driver design and data processing and imaging application design.The design of Android driver mainly completes the research on the general architecture of character device and the serial port driver of Linux kernel terminal device.For data processing and imaging application program design,a good interactive interface is provided for users in the UI design of the application program and the interface is preset for the subsequent data processing algorithm.Finally,Snell ray tracing technique is used to determine the propagation path of ultrasonic wave in concrete under test.The serial port communication technology is used to realize the communication between the data acquisition system,data processing and imaging applications.In order to ensure the reliability of data transmission,the serial port communication protocol is designed,and the CRC16 check code is used to complete the data verification.The imaging effects of the data acquisition system and the data processing and imaging applications were tested in the laboratory.Experimental results show that the concrete ultrasonic tomography detector has basically realized the basic functions of digital ultrasonic detection equipment,and the sensitivity is no more than 44.6 V,the dynamic range is 77 d B,and can match the ultrasonic probe frequency bandwidth of 10khz-750 khz.However,due to the problems such as too large mesh division of measured concrete and the need to improve the inversion imaging algorithm,the two-dimensional section imaging effect still needs to be improved.