Acoustic emission is generally high-frequency signal with the characteristics of broadband and burstiness, so it is very difficult to acquire acoustic emission signal in real time as well as rapidly, In this paper, an USB based acquisition system for acoustic emission signal is designed, which adopts CPLD as controller and uses two high-speed A/D converters to achieve synchronous acquisition of two-channel acoustic emission signals, The system first puts collected data into a FIFO and then transfers data to host through USB using CY7C68013, The sampling frequency of the system is up to 10MHz and the transmission rate of USB is 40M/S, Hard body impact test and lead-breaking test indicate that the system can achieve real-time acquisition of acoustic emission signal well,
Ultrasonic guided waves detecting technology has promising application prospects in structural health monitoring. In order to detect defects in the aluminum sheet, a kind of defect localization imaging algorithm, combining multi-parameter compensation and pixel partitioning optimization is proposed in this paper. Based on the analysis of imaging principles, the waveform signal of time domain was mapped onto the wavenumber domain through a backward propagation compensation, so dispersion parameters can be compensated. Reference signal compensation can be achieved by the baseline signal differential method from wavenumber domain, which overcame influences of environmental changes. During the imaging process, a reasonable threshold was used for pixel partitioning and optimization to improve image quality. Experimental results demonstrated that positioning error about the algorithm is small, defects imaging of sheet is clear and intuitive, this optimization and compensation of guided-wave defects imaging can be used in structural health monitoring.
The grinding wheel wear status is an important guarantee for the processing efficiency and processing quality of precision and super precision grinding. In this paper, a USB acoustic emission signal acquisition system is designed for online monitoring of grinding wheel status. In the system, CPLD is used as the controller, and a high-speed A/D converter is used to implement the synchronous acquisition of acoustic emission array signals. The collected data are sent into FIFO, and CY7C68013A is used for USB data transmission with upper computer. The sampling frequency of the system can be 10 MHz, and USB transmission speed can reach 40M/S. It is proved that it can meet the monitoring requirements of grinding wheel wear status well by the grinding processing.
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