Determination accuracy enhancement of viscoelastic constitutive model of optical glass

• Published in: Materials & design Vol. 236; p. 112513
• Main Authors: Liu, Guangyu, Fang, Fengzhou
• Format: Journal Article
• Language: English
• Published: Elsevier 01.12.2023
• Subjects: Aspheric lens; Finite element method; Precision glass molding; Viscoelastic constitutive model
• ISSN: 0264-1275
• DOI: 10.1016/j.matdes.2023.112513

This study proposes an effective method for improving the determination accuracy of the viscoelastic constitutive model via the combination of uniaxial creep with stress relaxation and the use of creep data to correct stress relaxation curves, known as “stress relaxation and creep correction (SRCC).” A typical molding glass was selected as the study material to fit and correct the constitutive model using the new method, and glass was regarded as a thermorheologically simple material to describe the temperature-dependent viscoelasticity. Glass cylinders were used in uniaxial compression stress relaxation experiments, which were conducted on a molding machine, and the experimental results were fitted with the generalized Maxwell constitutive model. The constitutive model was corrected further by optimization of the long-term modulus based on the SRCC method, and friction coefficients were calibrated under different molding conditions to improve the simulation accuracy. To verify the accuracy of the corrected constitutive model, we constructed a two-dimensional axisymmetric numerical model of molding biconvex aspheric lens and extracted and compared the molding displacement curves with experimental data. The results indicate that more accurate guidance for the optimization of the glass molding process can be provided based on the corrected model.