In order to detect the debond defect inside a certain solid rocket engine, the propagation model of soundwave in the multi-layer system was analysed in the paper. It was found that the complex impedance of the multi-layer system would shift the phase of the incident wave. Then, a simulation on a triple-layer medium system adhered by glycerin , steel and insulation was carried out, through which the relationship between the phase of reflection echo and the frequency of the incident wave was obtained under the circumstances of steel and insulation bonded well and debonded respectively, which confirmed the result of the theoretical analysis. It was also found that the phase difference between the debonded area and well-bonded area at some frenquencies is bigger than at others. Experiments were carried out on the defected engines and observed the phase of echo at 0. 99 fold phase hit frequency. The result shows that the phase of the observation point relates to bonding condition of the adhesive joint indeed. In conclusion, the method of phase analysis can be used to detect the adhesive quality of the multi-layer adhesive joint.%为了检测某型固体火箭发动机内部的脱粘缺陷,首先分析了声波在分层介质中的传播模型,发现分层系统的复阻抗将使入射波产生相移；然后对甘油、钢板和绝热层组成的三层媒质系统进行了仿真,得到钢板和绝热层脱粘和粘好两种情形下,反射回波的相位随入射波频率之间的关系,验证了理论分析结果,并发现在某些频率点处脱粘和粘好的相位差最大；对带缺陷的样品发动机展开了实验,在相位突变频率的0.99倍处观察回波信号的相位,结果显示粘接良好的部位的相位都在2.85rad以上且分布比较集中,而脱粘的部位相位基本在2.75rad以下；表明回波信号的相位与粘接状态有密切的关系,相位分析法可以用来检测多层粘接结构的粘接质量.
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