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针对普遍存在的航空发动机连接件松动故障现象,建立了单自由度集总质量模型,引入松动故障模型,利用数值积分方法求得系统响应,分析了非同步响应特征;利用对含松动间隙的连接件进行松动实验,发现了其加速度响应经过自相关降噪后,时域波形表现为明显的冲击特征,波形上下不对称,呈现“截头状”波形;频谱上表现为伪临界亚谐共振以及伪临界超谐共振;此特征与仿真结果一致,可以作为判定松动故障的典型特征。通过仿真发现,导致连接件出现该松动特征的原因在于:1)松动故障引起的刚度的变化;2)当刚度变化的周期等于振动周期时,将产生倍频现象,在特定频率下,将激发系统的临界频率;当刚度变化的周期等于n倍振动周期时,则将产生1/n分频及其倍频,在特定频率下,将激发系统的临界频率。
Aiming at the ubiquitous loosening failure phenomenon of aeroengine connector, a lumped mass model of single degree of freedom was established, a loose failure model was introduced, and the system response was obtained by using the numerical integral method. The unsynchronized response characteristics were analyzed. After the auto-correlation noise reduction, the time-domain waveforms show obvious impact characteristics, the waveforms are asymmetric up and down, showing “truncated” waveforms; the spectrum shows pseudo-critical sub-harmonic Resonance and pseudo-critical superharmonic resonance; this feature is consistent with the simulation results, which can be used as a typical feature to determine the loose fault. The simulation results show that the loosening characteristics of the connector are as follows: 1) the change of stiffness caused by loosening failure; 2) when the period of stiffness variation is equal to the vibration period, double frequency phenomenon will occur; at certain frequency, The critical frequency of the system; when the period of stiffness variation equals n times the vibration period, a 1 / nth frequency and its frequency multiplier will be generated, and the critical frequency of the system will be excited at a specific frequency.