热声载荷下薄壁开孔结构振动响应与寿命预估

Vibration Response Analysis and Fatigue Life Prediction of Thin-walled Structures with Opening under Thermo-acoustic Loads

金属薄壁开孔结构在强热声载荷下,表现出大挠度强非线性响应特性,疲劳寿命缩短。基于时域的基础上,利用有限元法(FEM)结合降阶模态法(ROM)获取4边固支开孔薄板在不同热、声载荷组合下的位移和应力的动态响应,并进行响应时间历程和功率谱(PSD)的统计分析。采用雨流计数法和Morrow平均应力模型,结合Miner线性累积损伤理论对结构进行疲劳寿命的预估和分析。结果表明:屈曲后的位移响应由热声载荷的相对强弱决定。此外,屈曲前结构随热、声载荷的增加,寿命缩短。屈曲后,持续跳变使得结构的寿命缩至最短;进入间歇跳变区域,间歇时间短的跳变要比间歇时间长的跳变造成的结构损伤大,即快频跳变引起的损伤更大。跳变结束后,随着温度的升高,寿命先延长后缩短。

The metallic opening thin-walled structures under the severe thermal-acoustic loadings exhibited large deflection and strongly nonlinear response and fatigue life was decreased. Based on time domain, by using finite element method （FEM） and reduced order modal method （ROM）, displacement and dynamic response of stress for clamped plate under different thermal-acoustic load combinations were obtained, the response time history and power spectral density （PSI）） were analyzed. Miner accumulative damage law was employed in conjunction with the rain-flow counting （RFC） method; fatigue life of structure was estimated and analyzed. Results show that response of post-buckled displacement is determined by relative strength of thermal-acoustic loadings. Besides, the fatigue life of pre-buckled plate decreases with the increase of thermal-acoustic loodings, and goas down to the lowest undergoing persistent snap-through at the post- buckled region. After enter intermittent snap-through region, compared with snap-through with longer intermittent time, the shorter one takes worse damage on the structure. Namely the damage caused by fast frequency snap-through is bigger. After snap-through, fatigue life goes up first,and then go down with the increase of temperature.