基于多点随机激励的发动机管路振动疲劳寿命分析

Vibration Fatigue Life Analysis of Engine Piping SystemBased on Multi-Point Random Excitation

关键词:  多点激励  功率谱密度  Dirlik模型  弹性约束

Key words:  Multi-point excitation  Power spectral density  Dirlik model  Elastic constraint

摘要:

针对航空发动机管路系统激振环境复杂、激振点多的现状和在此边界条件下单点随机振动方法无法准确分析与模拟的问题，提出了一种多点动力学振动分析方法，首先从理论上推导出多点激励的动力学振动方程，其次利用有限元模拟验证了结构多点振动的动强度响应特性，根据Dirlik模型预测了管路系统的随机振动疲劳寿命，对比分析了结构在多点振动激励与单点振动激励下响应动力学特性以及疲劳寿命的关系，针对载荷相关性问题探究管路应力响应与疲劳寿命的变化规律，最后针对于不同的约束条件，分析了弹性约束刚度值对于结构疲劳寿命的影响。对比分析发现：在多点激励下管路系统的的振动寿命仅为单点激励最低疲劳寿命的22.31%，管路应力响应与疲劳寿命随相位与相干系数变化而呈规律变化，随着约束刚度值的增加，结构的响应功率谱密度增加，结构共振区域对于功率谱密度放大作用减小，疲劳寿命降低，验证了多点动力学振动分析方法的有效性。

Abstract:

Aiming at the complicated exciting environment and many exciting points of the aeroengine pipeline system， the single point random vibration method can not be accurately analyzed and simulated under the boundary conditions. This paper proposes a multipoint dynamic vibration analysis method. Firstly， the dynamic vibration equation of multi-point excitation is deduced theoretically. Secondly， the dynamic response characteristics of multi-point vibration are verified by finite element simulation. According to the Dirlik model， the random vibration fatigue life of pipeline system is predicted. The dynamic characteristics and fatigue life of the structure under multi-point vibration excitation and single point vibration excitation are compared. The relationship between stress response and fatigue life of pipeline is explored according to load correlation. Finally， according to different constraint conditions， the effects of elastic constraint stiffness value on structural fatigue life are investigated. Comparative analysis found that the vibration life of pipeline system under multi-point excitation is only 22.31% of the minimum fatigue life of single point excitation. The stress response and fatigue life of pipelines change regularly with the change of phase and coherence coefficient. Moreover， with the increase of restrained stiffness， the response power spectral density of the structure increases， the amplification effect of the resonance region on the power spectral density decreases， and the fatigue life decreases. The validity of the multipoint dynamic vibration analysis method is verified.