Surface residual stress in soda-lime glass evaluated using instrumented spherical indentation testing

Instrumented spherical indentation testing is proposed as a non-destructive way to evaluate surface residual stress in soda-lime glass. 10 μm-deep indentations with a spherical indenter of 250 μm radius do not reduce the strength of 3.5-mm-thick soda-lime glass as measured in four-point bending tests. We find good linearity between the compressive surface residual stress and the force difference at maximum indentation depth in the indentation force–depth curve, while hardness as measured by instrumented spherical indentation testing is independent of compressive surface residual stress introduced by bending and strengthening heat treatment.