STUDY ON ELASTIC-PLASTIC COMPONENT IN INDENTATION FATIGUE OF SODALIMEGLASS

Fracture mechanics studies on glass by indentation has become predomin ant in recent times. Interest in it has become more prominent due to a large application of such materials in areas of engineering applicati ons encountering fluctuating stresses induced thermally, mechanically or physically. However, glass subjected to repeated indentation at a p oint prior to crack initiation with subcritical loads phenomenological to metal fatigue has not been systematically investigated. Repeated i ndentation at a single point with different subcritical loads (0.1N, 0 .15N, 0.25N, 0.50N, 1.0N) was performed till radial cracks occurred. T he length of the diagonal was measured after each indentation, which w as found to increase with indentation cycle eventually leading to crac k initiation. This observation was analysed considering the elastic pl astic component and the residual stress developed during each cycle. A mathematical model has been postulated to correlate the contribution of cumulative residual stress for crack initiation.