前言在超声探伤中,一般平晶片的探头在远声场(>N)时声束就开始扩散,因此对于厚工件中较远的缺陷,即使只是一个很小的点,如以6dB、12dB 或20dB 降落法移动探头来描述此缺陷的大小,势必形成一个大许多倍的区域。这个区域的大小不仅与声程的远近和探头的扩散角有关,而且还取决于缺陷的形状,尺寸和取向(即决定缺陷本身指向性的因素)。但后一 Foreword Ultrasonic flaw detection, the general flat-wafer probe in the far sound field (> N) when the sound beam began to spread, so for the longer artifacts thick workpiece, even if only a small point, such as 6dB, 12dB or 20dB Landing method to move the probe to describe the size of this defect, is bound to form a much larger area. The size of this area depends not only on the distance of the sound path and the angle of divergence of the probe but also on the shape, size and orientation of the defect (ie, the factor that determines the directivity of the defect itself). But after one