采用爬波对小径管内壁1 mm×5 mm（深度×长度）模拟裂纹制作DAC（距离-波幅）曲线，在距离小径管焊缝模拟缺陷10～20 mm间以直射波覆盖全焊缝扫查，水平定位可直接读取缺陷位置。当采用横波检测时，以ø1 mm横通孔制作DAC曲线，实测管内外壁1 mm×5 mm模拟裂纹时，其反射声压比DAC曲线高7～14 dB。试验结果表明，横通孔与点状和面状真实缺陷的反射声压差较大，如果采用小径管内壁等深模拟裂纹制作DAC曲线，在定量检测时可避免误差。

A DAC (distance-amplitude) curve for detecting the 1 mm×5 mm (depth times length) simulated crack of small diameter tube inner wall was made by using the creeping wave. If tested with a direct wave range covering the whole weld at a distance of 10-20 mm from the simulated pipe weld defects, the horizontal positioning can directly read the defect position with quantitative accuracy. When the shear wave was used and DAC curve was made through drill hole of diameter 1 mm, the reflected sound pressure for the simulated cracks (1 mm×5 mm) of both inside and outside the tube should be 7-14 dB higher than DAC curve. The experimental results show that the reflecting acoustic pressure by transverse through hole and point and planar defect has big difference, and therefore if making DAC curve by the equal depth simulated crack of small diameter tube inner wall, the quantitative errors can be avoided.