Correlation between multistage crack growth and time-dependent strength in commercial silicate glasses Part 1. Influence of ambient media and types of initial cracks

Abstract

The dependence of flexural strength upon loading velocity is studied regarding commercial glasses (sodium-borosilicate, sodium-aluminosilicate and soda-lime-silica glasses) in various ambient media (water, air, nonane, ethyl alcohol) after having produced various types of surface damage (emery paper, powder jet, Vickers indenter). This dependence (fatigue curves) is calculated by means of a numerical method based on data on macroscopic crack growth and compared with experimental results. Extension of the study to extremely high and low loading velocities allowed for experimental representation of multistage fatigue curves and also for their comparison with calculated results in a wide range from which some peculiarities of the subcritical growth of surface microcracks can be derived. On the other hand, the influence of ambient media on the life time of glass under stress could also be studied. It is pointed out that two factors are of great influence: the types of the initial cracks (part 1) and the treatment after damaging the surface but before performing the fracture tests (part 2 ) .