螺纹边界法对圆柱超声缓冲杆尾随脉冲干扰的抑制*

对于高温管道壁厚的超声波在线监测,需要超声波探头与缓冲杆搭配使用,以降低探头的接触温度。超声波在圆柱形缓冲杆的边界会发生波型转换,在缓冲杆的第一次和第二次底面回波之间产生等间隔的尾随脉冲干扰,影响管道内壁回波的识别与提取。该文创新性地采用螺纹边界法改变缓冲杆的边界特征以抑制尾随脉冲干扰,经实验验证螺纹边界法对尾随脉冲干扰有较好的抑制效果;不同螺纹螺距的实验对比表明,对于直径为20 mm的钢材料圆柱缓冲杆,在1 mm、2 mm和3 mm三种螺距中,螺距为2 mm的螺纹边界对5 MHz超声波的尾随脉冲干扰的抑制效果最强。

Restraining the ultrasonic tail pulses in cylinder waveguide rod with the thread boundary method

In the ultrasonic thickness monitoring of high temperature pipeline, ultrasonic probe and buffer rod need to be used together to reduce the contact temperature of the probe. Because of the ultrasonic wave-mode conversion at the boundary of the cylindrical probe waveguide rod, the uniformly spaced ultrasonic tail pulses will be produced between the first subface echo and the second subface echo, and these tail pulses may influence the identification and extraction of echo signal of the inner wall of pipeline. In this paper, the screw boundary method is proposed to change the boundary characteristics of the buffer rod and suppress the tail pulses. The experimental results show that the screw boundary method has a good inhibitory effect on tail pulses. Specifically, in the 20mm diameter cylinder steel buffer rod, the screw boundary with 2mm screw pitch has the strongest inhibitory effect on tail pulses of 5MHz ultrasonic wave among the screw pitches of 1mm, 2mm and 3mm.