基于BEEI方法的软包装热封缺陷超声检测研究

Defects Ultrasonic Detection in Seal Region of Flexible Package Using BEEI Method

将超声无损检测技术应用于软包装热封封口性能检测中,采用背散射回波包络积分(BEEI)成像方法,该方法将每一扫描点的时域回波信号进行Hilbert变换求其包络信号,将包络信号在整个回波时间段的积分值按照扫描的先后次序生成一个二维矩阵,对矩阵插值后进行成像.试验中,采用中心频率为22.66MHz的点聚焦探头,对软包装封口处直径为50—150μm的六种通道型缺陷和夹杂缺陷进行扫描,扫描区域为包含缺陷的2.98mm×1.50mm的矩形区;分析了成像矩阵中BEEI值的变异系数(CV)以及垂直于热封方向和平行于热封方向上BEEI值的变化趋势.结果表明,超声无损检测技术可以较好地应用于软包装热封质量的检测;试验所得的BEEI值的变异系数低于8%,说明整个成像矩阵中BEEI值的离散程度较小;缺陷区的BEEI均值高于背景区的BEEI均值约30%—40%.

Ultrasonic non-destructive testing method was introduced to detect flexible package seal quality.The channel defects with diameters of between 50 and 150μm in the seal area of flexible package were detected using Backscattered Echo Envelope Integral（BEEI） imaging method.The echo signal for each scan point in time-domain was Hilbert-transformed to produce its envelope,and was further integrated over the entire signal envelops to obtain the BEEI value.The BEEI value was calculated producing a two-dimensional BEEI-value matrix.The matrix was aligned into a rectilinear pattern mapped at the scan pattern grid,and then was interpolated.The final interpolated matrix was used to yield the gray scale image.The images were formed with a spot focused 22.66 MHz ultrasound transducer scanned over a 2.98 mm×1.50mm rectangular gird.Coefficient of variation（CV） values of BEEI-matrix for each sample were studied.The variations of the BEEI values in the direction vertical to the edge of the heat seal and in the direction parallel to the edge of the heat seal were compared.The results show that channel defects and inclusion defects in flexible package can be effectively detected using BEEI imaging method.The CV values are lower than 8%for channel and inclusion defect, which indicate the variation of the BEEI values in matrix is small.The mean BEEI values on the defect region are about greater between 30%and 40%than that on the background region.