Evaluation of indentation induced residual stress in the surface of float glass

Residual stress field around a Vickers diamond indentation was studied using float glass as a model specimen. The basis of the experimental technique is to use cracks from a small indentation as a microprobe to measure the residual stress at a specific point around a large indentation and to study the change of the residual stress by heat treatment. Residual tensile and compressive stresses around a large indentation produced by applying the load of 19.6 N were distributed up to the distance of about 300 μm from the indentation center. The tensile and compressive stresses were 10 MPa and -40 MPa, respectively, at a distance of 200 μm from the indentation center. The residual stress decreased by heat treatment and became zero by keeping the indented specimen at 550°C, a temperature which is close to the annealing point of the glass, for 2h. The depth of the indentation also decreased by heat treatment. This technique can be widely applied to study residual-stress-related phenomena in ceramics as well as in glass.