胶层固化对反射镜面形影响的仿真与试验

Simulation and experiment of influence of adhesive curing on reflective mirror surface

研究了用厚胶层进行光学零件之间的黏结操作时,胶层固化后其收缩力对反射镜面形的影响。首先,分析了胶层固化过程中胶层对光学元件产生拉应力的原理,找到了胶层固化过程中产生收缩力的主要因素。其次,建立了反射镜胶结组件的有限元模型,采用等效热变形法仿真分析了胶层收缩对反射镜面形的影响,分析发现胶层的等效线胀系数不能直接采用收缩率代替,而将材料的收缩率转换为胶层的等效线胀系数后,分析结果与试验结果吻合较好。最后,提出了减小胶层收缩对反射镜面形影响的改进方案。试验结果表明:黏胶方案改进后,胶层固化过程中的收缩力引起反射镜中心区域鼓包的PV值从0.574λ减小为0.064λ,镜面面形均方根值从0.127λ减小为0.038λ,这些结果显示胶层固化过程中产生的收缩力对反射镜面形的影响得到了显著改善。

The effect of shrinkage stress induced by adhesive curing on a reflective mirror surface was analyzed when the thick adhesive layer was used to joint optical elements. Firstly, the principle of ten- sile stress induced by adhesive layer to optical elements during adhesive curing was analyzed and the main factors of generating shrinkage stress were obtained. Then, a finite element model of the reflec- tive mirror set was constructed. The finite element analysis was carried out by using the thermal-to-shrinkage analogy and the thermal modeling tools were used to compute the adhesive curing shrink- age. The curing shrinkage was substituted by low temperature concentration, but the Coefficient of Thermal Expansion（CTE） value of the adhesive could not be taken place by the coefficient of adhesive shrinkage directly. After converting the coefficient of adhesive shrinkage to the equivalent CTE value,the analysis results are accord with the test results. Finally, the improved glue scheme was put for- ward on the basis of the analysis results. The experiment results indicate that the reflective mirrorsurface deformation（ PV value） has decreased from 0. 547λ to 0. 064λ, and the RMS value decreasedfrom 0. 127λ to 0. 038λ. This results mean that the effect of shrinkage stress in adhesive curing pro-cessing on the reflective mirror surface has improved greatly.