中文摘要：

针对海洋平台水下钢结构无损检测的需要,研究在空气和不同温度的水作为耦合介质的情况下,声发射波在钢结构传播过程中幅值和能量的变化趋势,以及声发射波幅值和能量损失的原因。基于声发射波反射原理,分析了声发射波在钢结构中传播的多径效应及波形转换特性,并解释了时域波形发生分离的原因。实验结果表明：水为耦合介质时声发射波幅值和能量损失较大;水温对声发射波幅值和能量几乎没有影响。

英文摘要：

In order to meet the needs of nondestructive testing of the underwater steel structures of offshore platforms,the trends and causes of amplitude and energy losses of acoustic emission waves propagating in steel structures in air and water as coupling media have been studied.Based on the reflection theory of acoustic emission waves,the multi-path effect and wave conversion have been analyzed and the cause of the dispersion of the time-domain waveform is explained.The experimental results show that：（1） the amplitude and energy undergo a significant loss with water as the coupling medium;（2） the water temperature has a negligible influence on the amplitude and energy.