焊缝结构中超声相控阵聚焦声场的数值模拟及分析*

针对焊缝内相控阵声场聚焦问题,建立焊缝结构中多高斯声束法的相控阵声场计算模型,分别用直接聚焦和底面反射聚焦两种方式对焊缝内部的相控阵声场进行数值模拟,分析不同方式下的相控阵聚焦声场特性,讨论不同区域适用的聚焦方式,分析了界面倾斜角度对聚焦效果的影响。结果表明,在相同焊缝结构条件下直接聚焦的方式更适合对厚壁焊缝的中下部进行聚焦扫描,在焊缝上表面附近,当声束偏转角大于80°时,直接聚焦方式无法有效聚焦;反射聚焦的方式更适合对焊缝上表面附近区域进行聚焦扫描,随着焦点深度增加,反射聚焦的声束偏转角增大,当声束偏转角大于55°时,反射聚焦无法形成明显焦点;两种聚焦扫描方式可形成有效的互补。当设置的焦点固定时,直接聚焦的实际焦点随界面倾斜角度增大向预设点远处偏移,而反射聚焦的效果基本不受倾斜角的影响,实际焦点始终在预设焦点附近。

Simulations and analyzation of phased array focus sound field in the welds

The multi-Gaussian acoustic beam phased array sound field calculation model in the weld structure is established. The different numerical simulations of focusing sound field which include direct focusing and bottom reflecting focusing are performed to analyze the characteristics of phased array focusing sound field, discuss applicable focusing method to different areas and analyze the influence of the interface tilt angle on the focusing effect. The results show that in a same weld structure the direct focusing method is more suitable for focusing middle and lower parts of thick-walled welds. In the vicinity of upper surface of the weld, when the beam deflection angle is greater than 80°, this method cannot effectively focus. And the reflecting focusing method is used to scan upper surface of weld seam. The depth of focus increases, the deflection angle of the reflected beam increases, when the angle is greater than 55°, this method cannot form a significant focus. The two focusing scanning methods can form an effective complementary. When focus is fixed, the actual focus of the direct focus shifts toward farther away from the preset point as the interface tilt angle increases. The effect of reflecting focus is not substantially affected by the tilt angle, and the actual focus is always near the preset focus.