Investigation of the effect of coefficient of thermal expansion on prediction of refractive index of thermally formed glass lenses using FEM simulation

► During cooling in glass forming, refractive index changes due to structural relaxation and must be properly considered prior to manufacturing. ► A finite element model is established to accurately simulate structural relaxation of glass during cooling to predict refractive index changes. ► This study shows that the success of the simulation model depends on the accuracy of material information available to the lens manufacturers. ► Generic coefficients of thermal expansion are inadequate for predicting glass volume change. Thus a reverse calculation method was presented. ► Finite element simulation also showed that liquid coefficient of thermal expansion has a major effect on simulation versus fraction parameter.