Modeling the hydrodynamic impact on the tool influence function during hemispherical subaperture optical polishing.

Area of Science:

• Optics fabrication
• Mechanical engineering
• Materials science

Background:

• Deterministic control of material removal is crucial for high-precision optics.
• The tool influence function (TIF) governs material removal during subaperture polishing.
• Accurate modeling of pressure distribution within the TIF is essential.

Purpose of the Study:

• To analyze the pressure distribution within the TIF during subaperture tool polishing.
• To investigate the influence of tool deformation and fluid film thickness on pressure profiles.
• To understand the role of shear forces and fluid dynamics in material removal.

Main Methods:

• Finite element analysis (FEA) was employed to couple solid mechanics and fluid dynamics.
• Experimental parameters from published work were modeled.
• Pressure distribution, shear contribution, and fluid velocities were simulated.

Main Results:

• A flat-top pressure profile was observed, differing from Hertzian predictions.
• Tool deformation significantly influences fluid film thickness and pressure distribution.
• Shear forces were identified as a key contributor to material removal, especially at the contact edge.
• Simulated fluid velocities indicated mixed-mode contact polishing and hydroplaning effects.

Conclusions:

• The study provides a more accurate model of pressure distribution in subaperture polishing.
• Shear forces and hydroplaning are critical factors influencing material removal rates and precision.
• Findings support recent experimental observations on material removal drop-off due to hydroplaning.