高温环境下薄壁结构声激励响应及疲劳分析与试验验证

Acoustic excitation response and fatigue life analysis and test verification of thin-walled structure under high temperature environment

针对航空发动机薄壁结构热声疲劳问题,采用耦合的有限元/边界元法,对GH188薄壁结构进行动力学响应计算,采用改进的雨流计数法和Morrow平均应力模型,结合Miner线性累积损伤理论对薄壁结构疲劳寿命进行了预估。基于高温行波管试验器开展了GH188薄壁结构高温声激振疲劳试验研究,获取了薄壁结构在不同温度和声载荷作用下的模态频率、应力/应变响应和疲劳寿命结果。仿真计算结果与试验结果对比分析表明:数值仿真对结构破坏位置判断准确,破坏位置均为结构根部,结构1阶热模态频率具有一致性,误差0.49%～2.09%之间,X方向应力响应峰值集中在基频附近,随温度升高,结构发生软化刚度下降,响应峰值向左发生偏移,且预测水平与试验一致,误差在1%～3%之间,验证了薄壁结构热声响应计算方法与计算模型的准确性。结构疲劳寿命随温度和声压级的上升而均呈现下降趋势,疲劳破坏时间的预估值与试验结果在一个量级之内,误差在3～3.5倍之间,满足工程级寿命预测要求,验证了薄壁结构热声疲劳寿命预估方法的有效性。

To solve thermal-acoustic fatigue of aero-engine thin-walled structure,the coupled finite element method/boundary element method was used to calculate dynamic response of GH188 thin-walled structures.Based on the theory of Miner liner fatigue accumulative damage,an improved rain-flow counting method and a Morrow mean stress model wereadopted to estimate the fatigue life of thin-walled structures.With the use of high temperature travelling wave tube tester,GH188 thin-walled structure high temperature acoustic vibration fatigue test was conducted to obtain modal frequency,stress/strain response and fatigue life results of thin-walled structure under different temperatures and acoustic loads.It was shown in the contrastive analysis of the simulating calculation and test results that numerical simulation had accurate location judging for structural damage positions,all in the rooted positions of structures.The first-order thermal modal frequency was of consistent structures,with errors between 0.49%-2.09%,and X-stress response peaks were centered on fundamental frequency.With the rise of temperature,structure softening and stiffness reduction occurred,and response peak moved to the left;as the prediction level was consistent with the experiment,errors were between 1%-3%,validating the accuracy of thin-walled structure calculation method and model thermal-acoustic response.Structure fatigue life showed a decreasing trend with the increase of temperature and sound pressure level,and the predicted value of fatigue life and the test result were in the same order of magnitude,with the error between 3-3.5 times,satisfying the requirements of engineering level life prediction,and validating the effectiveness of simulation method for predicting thermal-acoustic fatigue life of thin-walled structure.