Numerical simulation and experimental study of residual stresses in compression molding of precision glass optical components

Compression molding of glass optical components is a high volume near net-shape precision fabrication method. Residual stresses incurred during postmolding cooling are an important quality indicator for these components. In this research, residual stresses frozen inside molded glass lenses under different cooling conditions were investigated using both experimental approach and numerical simulation with a commercial finite element method program. In addition, optical birefringence method was also employed to verify the residual stress distribution in molded glass lenses. Specifically, optical retardations caused by the residual stresses in the glass lenses that were molded with different cooling rates were measured using a plane polariscope. The measured residual stress of the molded glass lenses were compared with numerical simulation as a validation of the modeling approach. Furthermore, a methodology for optimizing annealing process was proposed using the residual stress simulation results.