超高速摄影中铍转镜静力学与动力学性能分析

Mechanical analysis on beryllium rotating mirror of ultra-high speed camera

基于弹性力学空间问题基本方程、线性振动系统运动方程及有限元法,提出转镜力学特性的数值分析方法.运用该方法得出转镜镜面变形量、内部应力分布和振动模态参量的定量数值:在边缘线速度600m/s下,三面体铍转镜的最大变形量为约0.3346μm;最大应力0.204GPa,位于轴孔附近并与镜面距离最短处;两个在互相垂直平面内的一阶弯曲振动模态发生在3.4×105r/min附近,一阶扭振点位于5.13×105r/min附近,两个二阶弯曲振动点位于6.6×105r/min附近.结果表明,如制造无缺陷,由体力产生的静载荷不足以破坏镜体,对转镜产生较大破坏作用的是共振导致的疲劳破坏.

The methods of numerical analysis for the strength and modal of rotating mirrors were presented based respectively on the three-dimensional elastic mechanics and dynamics. On strength computation, the finite element models of rotating mirror were established according to the real structure of the mirror, and the rotating three-faced beryllium mirror were analysed. Results display that the surface deformation magnitude of the mirror is approximately 0. 334 6 μm, and the maximum stress is 0. 204 GPa at 600 m/s of edge linear speeed. The regions of maximum stress are on the axial hole and symmetric to symmetrical planes of mirror body, and keep beelines to surfaces. On the modal analysis, the results show that the first and second modals of bending vibration exist around 3.4 × 10^5 r/ min and 6.6 × 10^5 r/min, which appear binate and orthogonal respectively, and another modal belongs to the first torsional vibration that occurs by 5. 13 ×10^5 r/min. Analysis indicates that endurance failure by resonances plays vital role for mirror failure rather than static load by body force if manufacturing defects are of nonexistence.