采用声发射技术监测带有表面焊接裂纹的箱形梁结构的三点弯曲试验。分析了箱形梁试件受载弯曲过程中裂纹扩展的声发射信号特征，比较了加载过程中不同载荷水平下定位源信号的声发射参数特征。研究发现，表面裂纹扩展的声发射信号为突发型信号，其幅度主要为45～60 dB，频率主要分布在100~450 kHz。试验结果表明，线定位方法可以对箱形梁试件中的裂纹缺陷进行准确定位。

The AE technique was used to monitor the box beam with external crack on the crane during the three-point bending test. The characteristics of AE signals with crack propagating were analyzed. The parametric characteristics of the location sources were compared on the different load level in the test. The research proved that the signals of the crack propagating were burst emission with its amplitude distribute being from 45 to 60 dB mainly and frequency domain being from 100 to 450 kHz. The results indicated that the linear location method could be used well for the AE sources location of box beam when the external crack was propagated during the three-point bending test.