Research On Topological Optimization Design Of Space Optical Mirror Based On Additive Manufacturing

In recent years,with the rapid development of space remote sensing technology at home and abroad,it has played an increasingly important role in the fields of meteorology,military,astronomy and so on.As the key optical element of space telescope,with the increasing demand for space telescope,the index requirements of its lightweight degree,surface accuracy and development cycle are also improving.In this paper,the spatial optical mirror with an aperture of 500 mm is taken as the object,and the following research work is carried out:In the first part,the different working conditions of the mirror from preparation stage,launch stage to on orbit operation stage are described in detail;Combined with classical theoretical analysis and finite element analysis,the initial structure scheme of 500 mm aperture mirror is determined.The second part is the lightweight design of mirror.According to the principle of topology optimization,the topology optimization design is carried out on the basis of the traditional stiffener structure design.After adopting the traditional empirical design and the topology optimization design based on this scheme,the research on the direct topology optimization of solid mirror is carried out.The mass of the mirror obtained by the three design methods is 7.00 kg,5.24 kg and 4.75 kg in turn.Among them,the surface accuracy of the topology optimization of the solid mirror is the best and the degree of lightweight is the highest.It shows that the topology optimization method can not only effectively improve the shape accuracy of the mirror,but also improve the lightweight rate,and the structure weight and surface shape accuracy obtained from the direct topology optimization of the solid mirror are lighter,which provides a reference for the rapid design of the innovative lightweight structure on the back of the mirror.In the third part,the supporting structure of the mirror is designed,and the static and dynamic analysis of the mirror assembly is carried out.The analysis results show that the shape accuracy of the reflecting mirror under the condition of X,Y and Z self weight and2-degree uniform temperature rise can meet the design index requirements;The fundamental frequency of the mirror assembly is 230.3 Hz,indicating that the dynamic stiffness is sufficient to effectively avoid resonance with the whole machine structure;Under the X,Y and Z low-frequency sinusoidal excitation,the maximum magnification of the acceleration response of the mirror assembly meets the index requirements of less than10 times;Under the X,Y and Z random vibration excitation,the mirror assembly meets the requirements of structural failure 3σ principle.The mirror assembly meets the design index requirements under static and dynamic conditions,which shows that the design is reasonable,the structure is stable and reliable,and the mirror can work normally in different environments,which provides a reference for the component design of innovative structural mirror.The fourth part is the additive manufacturing test of topology optimization mirror.Taking PLA(non engineering material)as the material,the topology optimization mirror is3 D printed by FDM method.This method has low cost and high speed.It verifies the actual lightweight degree of the topology optimization mirror structure designed in this paper.At the same time,it provides a reference for the shape finding of subsequent engineering materials,reduces the trial and error cost and improves the success rate of 3D printing.On the basis of the previous process test,taking aluminum alloy(engineering material)as the material,the reduced scale model of the mirror is printed by SLM method.The test results show that it has high structural reduction,short processing cycle and good forming effect.While retaining the topology optimization structure by using additive manufacturing technology,it provides a new idea for the rapid and efficient development of the mirror.