| The surface distortions of the primary mirror of the SOAR telescope are a major concern. Due to its nonhomogeneous coefficient of thermal expansion, the distortions after a temperature change have to be minimized. The goals of this research project are: first, to construct the finite element models which will allow a detailed study about interfacial mechanics; second, to obtain a near-circular form of surface distortions (i.e. minimize global warping).; Due to the material and geometric complexities of the primary mirror, finite element method was adopted to analysis the problem. The validation for adopting the finite element software, MARC, has been verified by analytical solutions and supported by another software, ANSYS. A FORTRAN code was developed to assist the software to capture the variation of coefficient of thermal expansion within each mirror boule. Axisymmetric analyses were adopted to study the interfacial mechanics and predetermine suitable boule placement combinations. After the studies and trials, a satisfactory semi-circular form of surface distortion was achieved. 10 cm thick mirror was proved to be an appropriate design. The maximum principal stresses were far less than the material ultimate strength. |
