Estimation of handling stresses in a 4 m Zerodur blank with the finite element method

Abstract

During handling of large Zerodur blanks for astronomical applications, the risk of a break due to an improper procedure is rather high. Using the example of a 4 m Zerodur blank produced by spincasting, this paper demonstrates that the finite element method can be used to estimate the handling stresses in advance. In this way, critical situations can be avoided. Two typical situations are investigated: the position of the blank on 4 or 2 support points, and the moment where the blank is standing vertically during a turning movement. Only static stresses produced by gravity are computed (no further accelerations). The results show the magnitude and distribution of the resulting first principal stresses.