热声载荷下薄壁开孔结构振动响应与寿命预估

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。

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

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 (PSD) 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 loadings, and goas down to the lowest undergoing persistent snap-through at the postbuckled 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