基于FPGA和LabVIEW的超声波螺栓应力测量系统设计

Design of Ultrasonic Bolt Stress Measurement System Based on FPGA and LabVIEW

针对传统螺栓应力测量方法的局限性,基于声弹性效应建立了超声螺栓轴向应力测量系统。测量系统由以FPGA为核心的下位机与基于LabVIEW的上位机两部分组成。研制了基于FPGA的超声激励、采集和传输控制模块,能灵活产生不同频率、不同周期数的高电压超声激励脉冲信号,以适应不同频率探头和不同类型螺栓对激励信号的要求。针对应力测量中超声回波信号周期重复的特征,系统结合等效时间采样法、三次样条插值法和平均值法,提高了螺栓轴向应力测量精度。试验结果表明,所建立的系统成功实现了螺栓轴向应力的精确测量,应力测量不确定度约为1.2 MPa。

Aiming at the limitation of traditional bolt stress measurement method,an ultrasonic bolt axial stress measurement system was established based on acoustic elastic effect.The measurement system consists of two parts, the lower computer based on FPGA and the upper computer based on LabVIEW.An ultrasonic excitation,acquisition and transmission module based on FPGA were developed.It can flexibly generate high-voltage ultrasonic excitation pulses of different frequencies and periods to meet the requirements of different frequency probes and different types of bolts for excitation signals.Aiming at the periodic repetition of ultrasonic echo signal in stress measurement,the system combined equivalent time sampling method,cubic spline interpolation method and average method to improve the accuracy of bolt axial stress measurement.The test results show that the system successfully realizes the accurate measurement of bolt axial stress,and the uncertainty of stress measurement is about 1.2 MPa.