New testing and calculation method for determination viscoelasticity of optical glass

Abstract

New testing and calculation method for determination viscoelasticity of optical glass," Opt.

Deformation Analysis of the Glass Preform in the Progress of Precision Glass Molding for Fabricating Chalcogenide Glass Diffractive Optics with the Finite Element Method

“…The actual pressure σ α1 (t) applied to the upper surface of the glass can be expressed as Equation (10). The projection radius, Rp(t), of the lower contact surface shown in Figure 8b can be expressed by Equation (11). The normal force, Fn(t), applied to the lower contact surface can be expressed by Equation (12).…”

“…Precision glass molding (PGM) technology is a cost-efficient process for the production of micro/nanostructured glass components with complex surface geometries [6][7][8]. It is a technology that deforms glass preform into the desired shape by use of molds at a high temperature in an inert or vacuum environment [3,[9][10][11].…”

“…Around the molding temperature, ChG is in a viscoelastic state [10]. The finite element method has become an efficient method for PGM for predicting the molding force, profile deviation, residual stress of the lens, and birefringence distribution, and for designing the appropriate processing parameters for industrial purposes [3,11,20,21]. Zhou et al analyzed the refractive index changes of ChG As 2 S 3 lens with the cooling rates of finite element method (FEM) to verify and modify the calculated stress relaxation function [22].…”

Modeling nonequilibrium thermoviscoelastic material behaviors of glass in nonisothermal glass molding

“…Despite its importance, modeling the thermoviscoelastic behaviors of nonequilibrium glass‐forming systems has not been carried out in earlier studies. In fact, most of the previous works solely attempted to characterize the material behaviors of glass in its equilibrium regime 9–12 . More specifically, glass specimens were equilibrated by a long temperature holding before the mechanical loads were applied where the viscoelastic responses, either creep or stress relaxation depending on the type of loading, were measured under an isothermal condition.…”

“…In fact, most of the previous works solely attempted to characterize the material behaviors of glass in its equilibrium regime. [9][10][11][12] More specifically, glass specimens were equilibrated by a long temperature holding before the mechanical loads were applied where the viscoelastic responses, either creep or stress relaxation depending on the type of loading, were measured under an isothermal condition. As such, this procedure is valid only if glass undergoes no temperature changes during the forming process such as isothermal glass molding.…”