基于二进制编码的管道缺陷超声检测方法研究

Research on Ultrasonic Testing Method of Pipeline Defects Based on Binary Coding

脉冲信号激励的超声波用于管道缺陷检测时,存在平均发射声功率小及探测信号频带单一的局限,且在多发多收的阵列检测场合,很难确定接收回波的发射源,不利于被测体全声场的声学特征参数解算。为此,提出了采用正弦波频率调制的二进制超声编码方法检测管道缺陷。建立传感器编码激励响应的数学模型,通过仿真得到了传感器在不同激励频率、分数带宽和码位数下的幅频响应规律,并实现了对接收信号的有效区分和发射声源的有效标识。将该方法用于管道缺陷的超声检测,实现了管道不同种类缺陷的有效检出和发射声源的有效标识,并分析了二进制编码激励方式下缺陷对不同频带的敏感性。统计结果表明,2～4位码对管道渗漏孔和裂纹缺陷的检出率高于62%,对回波信号的标识正确率高于97%。

When the normal pulse signal excited ultrasonic wave was used to detect the pipeline defects,there was a limitation that the average transmitted sound power was small and the band of detection signal was single,and it was also very difficult to determine the emission source of echoes and calculate the acoustic characteristic parameters of the whole sound field in the tested body in the cai^of the array detection with multi-emission and multi-re-ceive.Therefore,a binary ultrasonic coding method using sine wave frequency modulation to detect pipeline defects was proposed in this paper.The mathematical model of the coding excitation response of the sensor is established.The amplitude-frequency response of the sensor under different excitation frequencies,fractional bandwidths and code bits is obtained by simulation.The received signal is distinguished and the transmitted sound source is identified effectively.Finally,the method is applied to the ultrasonic testing of pipeline defects,and the effective detection of different kinds of pipeline defects and effective identifications of emission sources are realized.The sensitivity of the defects to different frequency bands in binary coded excitation mode is also analyzed.The statistical results show that the detection rate of 2~4 bit code for pipeline leakage holes and crack defects is higher than 62%,and the correct rate of echo signal identification is higher than 97%,