Stress characterization of surface damages on soda-lime glass using a nanocontact deformation method

A nanocontact deformation method was used to measure the local and graded residual stresses around contact damages. By analyzing influences of the residual stress on nanocontact deformation itself instead of measuring the secondary crack emanated from it, 0.65 μm spatial resolution, which was superior to the highest level 1.8 μm attained by previous indentation fracture mechanics tests with an acute cube-corner indenter, was obtained with a general Berkovich indenter. However, a stress model combined with the nanocontact deformation provided only average stress variation around the contact damages. Thus, a resolution of two principal components from the residual stress in a biaxial state has been attempted in this study. By introducing radial microcracks around artificial microVickers damages, a crack-normal circumferential stress component disappeared and a series of nanoindentations close to the microcrack line yielded a variation of the radial stress component. By comparing this result with the average stress variation mentioned above, the crack-opening circumferential stress was measured and showed a good consistency with the previous study in soda-lime glass. In addition, distinctive features of present method were compared with previous indentation fracture mechanics method.