ABSTRACT
If the load is held constant, the indenter continues to sink into the material due to time-dependent deformation. This is called creep. It can happen even at room temperature in polymeric materials. However, in the case of brittle solids like glass and ceramics, the creep happens typically at a temperature more than half of its homologous temperature. In such cases, it can happen
when the applied stress is suddenly changed at a constant temperature. It can also happen when the temperature is suddenly changed when the material is held under constant applied stress. There are many other issues involved with creep deformation and the prevalent mechanisms, but that is beyond the scope of our present discussion. Because our main focus area in this book is nanoindentation of brittle solids, it suffices to know for the time being that there has not yet been any significant reported observation on room-temperature creep in brittle solids. After the predesignated hold time is over (region CD in Figure 6.1), the load is withdrawn through a predesignated period of time. How does the indenter feel about it? Well, the indenter starts to relax as the load continues to decrease at a given rate.
