Fractographic strength estimations of 1- and 2-step, ion-exchanged glass plates fractured in bending

Fractography is routinely applied to estimate the fracture strength of annealed brittle materials, however, it is rarely used in chemically strengthened (CS) glasses displaying significant residual stress. This work expands and improves upon a recently proposed fractographic strength estimation method applicable to CS glass plates with deep, 1-step residual stress profiles and no stress relaxation. In particular, the current work considers both CS soda-lime silicate glass with significant stress relaxation and 2-step, ion-exchanged lithium aluminosilicate glass plates. The proposed methodology and its limitations are discussed in light of extensive testing and analysis carried out on numerous CS glass plates. The accuracy of the proposed correlation between non-dimensional strength and mirror radius was validated on both 1-step and 2-step ion-exchanged glass plates with a relatively small case depth and relatively large, induced surface damage.