热声载荷下薄壁结构非线性振动响应分析及疲劳寿命预测

Nonlinear vibration response analysis and fatigue life prediction of a thin-walled structure under thermal-acoustic loading

基于时域分析法研究了金属薄壁结构在热声载荷下的非线性振动响应特性,并采用四种应力寿命模型预测了薄板梁的热声疲劳寿命。以典型薄板梁为研究模型,首先研究了单一噪声激励下薄板梁的时域响应特性及热载荷对其响应特性的影响机理,并仿真分析了薄板梁在热声激励下的非线性响应特性。在此基础上,运用雨流法统计了薄板梁根部的应力响应,并基于Miner线性累积损伤理论采用Goodman、Morrow、Walker和修正Walker应力寿命模型预测了薄板梁在不同工况下的热声疲劳寿命。研究结果表明:薄板梁的热模态基频在其热声疲劳问题中起主导作用;薄板梁热屈曲后的非线性跳变响应将增大应力幅值,从而严重削弱结构的预期寿命;噪声载荷是影响屈曲前薄板梁热声疲劳寿命的主要因素,而热载荷是影响屈曲后热声疲劳寿命的主要因素。因此在薄壁结构抗热声疲劳设计中必须重点考虑热声载荷联合作用的影响。

The thermal-acoustic vibration response characteristics of metallic thin-walled structures were investigated based on the time-domain analysis method, and four kinds of stress life models were employed to predict the thermal-acoustic fatigue life of a clamped thin-walled aluminum beam. Time-domain response characteristics of a typical beam model under acoustic loading and thermal-acoustic loading were determined, respectively via numerical simulation. Its nonlinear response behavior was simulated and analyzed under thermal-acoustic lading. Furthermore, the rainflow counting method was used to do statistics of the stress response at the root of the beam. Its fatigue life was predicted based on Miner linear cumulative damage theory and using 4 stress fatigue models including Goodman, Morrow, Walker, and modified Walker. The results showed that the thermal modal fundamental frequency of the beam in thermal-acoustic fatigue problems is predominant; the snap-through motion between the beam＇s multiple post-buckled equilibrium positions introduces very high alternating stress weakening the fatigue life expectancy of the beam ; acoustic loading is a major factor affecting the pre-buckled fatigue life of the beam, while thermal loading is a major factor dffecting the post-buckled fatigue life of the beam; therefore, anti-fatigue design of a thin-walled structure under thermal-acoustic loading must study the effects of combination action of thermal-acoustic loading.