中文摘要：

偏置磁场的合理设计是磁致伸缩式纵向超声导波传感器设计的关键之一，大直径管道中偏置磁场由于管径较大的原因而呈现磁场强度弱、分布不均匀的特点。通过有限元软件模拟了直径为88mm的大直径管道中各种磁路偏置磁场的分布情况，得到了不同截面磁场分布方差随磁路组个数增加呈现的对数衰减规律，中截面上偏置磁场与磁路组个数呈现线性递增的关系。结果表明5磁路组设计为88mm大直径管道超声导波磁致伸缩传感器偏置磁场的最优化阵列组合。

英文摘要：

The reasonable design of bias magnetic field is one of the key factors of longitudinal modes guided wave sensor based on magnetostrietive effect. The purpose of this paper is to study the distribution regularity of the bias magnetic field in large diameter pipes. Different magnetic circuits for an 88 mm diameter pipe was discussed based on numerical simulation and the distribution variance was used to measure the uniformity of the bias magnetic field. The result showed the distribution variance presented logarithm type attenuation with the increment of magnetic circuit number and finally a five-magnetic-circuit bias magnetic field was chosen for the magnetostrictive sensor.