The Research On The Effect Of Microcracks On Service Life Of The Space Optical Element

Micro-crack is one of the most effective factors to the intensity and service life of the space optical element (SOE). Because of the micro-crack in the surface, the actual strength of optical glass is less than one-percent of its theoretical strength, and its service life depends on the propagation velocity of the micro-crack.The mechanisms for the formation and propagation of micro-crack are discussed in this paper. A side-testing method for measuring the depth of the crack layer is presented. By using SEM electron microscope to observe glass surface etched by HF, a three-dimensional geometric model of micro-crack is obtained. According to the depth of the crack layer, a more reasonable process redundancy of fine-grinding and polishing in optical production is given. Calculations based on the fracture mechanics theory to the strength and service life of the SOE are given. Three ways based upon analysis to extend the service life of SOE are put forward.