Twyman effect mechanics in grinding and microgrinding

Area of Science:

• Materials Science
• Optical Engineering
• Surface Metrology

Background:

• The Twyman effect describes the bending of glass plates due to grinding-induced residual stress.
• Understanding this effect is crucial for precision optics manufacturing.

Purpose of the Study:

• To correlate experimental data on the Twyman effect in optical glasses.
• To investigate the influence of abrasive size and grinding conditions on residual stress.

Main Methods:

• Analysis of literature data on loose abrasive grinding (lapping).
• Review of deterministic microgrinding experiments using bound diamond and loose abrasives.
• Correlation of grinding parameters with glass mechanical properties.

Main Results:

• Grinding force and compressive layer depth correlate with fracture properties like indentation crack size.
• Larger abrasive sizes lead to decreased surface compressive stress and increased layer depth.
• In ductile-mode grinding, stress approaches the glass's yield stress.

Conclusions:

• Abrasive size is a key parameter controlling residual stress and bending in ground optical glass.
• Glass mechanical properties (hardness, Young's modulus) influence abrasive penetration and surface roughness.
• Ductile-mode grinding offers potential for achieving high surface compressive stress.