FAST索网高应力幅变位疲劳问题的优化分析

INVESTIGATION ON FATIGUE LIFE OF FAST CABLE-NET UNDER HIGH STRESS AMPLITUDE PRODUCED BY LONG-TIME ACTIVE

五百米口径射电望远镜(FAST)采用柔性索网作为主要支承结构,根据拟定的变位策略要求,通过促动器连接下拉索控制索网变位实现巡天观测。由于变位观测过程中索网将长期承受高达约500MPa的疲劳载荷,约为目前相关标准规定值的两倍多,故索网结构将是该望远镜中的关键易损部位。为此,该文以索网结构后期运行、监测及维护为背景,通过量纲分析方法明确影响索网变位应力幅值的主导因素,基于大型有限元软件ANSYS建立索网模型进行连续变位仿真分析,探索合理的变位策略以降低索网变位过程中的应力变化幅值,提高索网运行的可靠性。

A five-hundred-meter Aperture Spherical radio Telescope （FAST） is supported by a cable-net structure, which enables its surface to form a paraboloid in real time under active control. However, such form-changing operation would lead to about 500MPa of a fatigue stress range for the cable-net structure. This stress range is more than twice as that defined by the relative standard. Therefore, the cable-net structure is the most critical part of a FAST reflector system. Obviously, the fatigue stress will have a significant impact on the reliability of FAST during its service life. The dimensional analysis is used for studying main factor which affects the stress range of structure. Based on the finite element software ANSYS, the form-changing of cable-net structure is simulated. At last, optimal form-changing strategy is proposed for releasing the fatigue stress of cable-net structure, which would be in favor of improving the reliability of a cable-net structure.